GB2571988A

GB2571988A - Container planting system

Info

Publication number: GB2571988A
Application number: GB1804197.0A
Authority: GB
Inventors: Caffall Finch Steven
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-15
Filing date: 2018-03-15
Publication date: 2019-09-18
Anticipated expiration: 2038-03-15
Also published as: GB2571988B; GB201804197D0

Abstract

A plant 103 is grown permanently in a planting container 90 alongside at least one root ingrowth container 22, 24 which occupies a substantial volume of the planting container. Each ingrowth container has a perforated wall (3, figs 1-4) through which roots 100 grow into an ingrowth cavity. An extraction tool 30 is inserted into the open end 5 of one of the ingrowth cavities and a cutting head 40 with a lead screw is operated to extract roots 100 and growing medium 110. The cavity is then refilled with fresh growing medium so that the roots can re-grow. By refilling the ingrowth cavities in rotation fine roots continually develop in renewed soil. The containers may be integral. The ingrowth container may be ceramic or steel in a range of specified sizes with a defined bursting pressure and crushing pressure.

Description

Container planting system

This invention relates to the cultivation of plants in containers, and particularly to methods for maintaining a healthy root structure in container grown plants.

Plant root growth can be measured in natural envivonments using root ingrowth cores, typically bags of small polyethylene mesh, as described in GLBRC089: Below Ground Net Primary Production- GLBRC BCSE Sites (Kellogg Biological Station) - available at https://lter.kbs.msu.edu/protocols/157

The root ingrowth core is filled with soil and buried in the ground, where it becomes populated by the large and small roots of nearby plants. After some time the core is removed and examined to determine the rate of root ingrowth, as shown for example in Rivera-Monroy, Victor H., Root ingrowth core after 2 years of deployment, Taylor Slough (2003). FCE LTER Photos. 103. - available at http://digitalcommons.fiu.edu/fce_lter_photos/103

Alternatively, an annular core or root ingrowth donut can be left in the ground and the contents extracted at intervals, as shown at http://sev.lternet.edu/content/root-ingrowth-donuts-below-ground-biomass-0

A root ingrowth core can also be sampled by vacuum extraction using a casing driven into the centre of the core, as described in

Chad S. Boyd and Tony J. Svejcar, A Technique for Estimating Riparian Root Production, Rangeland Ecology & Management 62(2):198-202. 2009 - available at https://doi.Org/10.2111/08-182.l

By sampling roots from root ingrowth cores over an extended period in the same location it is known that the fine roots (less than about 2mm in diameter) of a plant growing in a natural environment tend to be ephemeral. Thus the root structure is continuously renewed as the fine roots die and are replaced by new ones which can extend to occupy new areas of the ground.

In contrast, the root structure of a container grown plant is of course constrained by the walls of the container, and can be examined simply by removing the plant from its container. Thus it is commonly observed that plants grown in traditional nursery containers exhibit circling root growth, with each root being axially elongated with little branching. This contrasts with the more highly branched root structure observed in natural environments and is known to stunt the development of the plant after it is transferred from the container to its final planting position in the ground.

In order to prevent this habit and encourage a more branched root structure in container grown plants, it is known to provide a nursery container with apertures or entrapment structures which cause the root tip to become entrapped or dehydrated by contact with the outside air. This suppresses axial root growth and promotes lateral branching, creating a more dense and highly branched root structure within the container.

For example, US4442628 and US7210266 B2 disclose plant containers with air pruning apertures.

GB2045044 A discloses a container having a finely perforated sidewall, in which a plant can be planted in the ground or in a nutrient medium so as to constrain the development of its root structure while developing normally above ground.

US4098021 discloses a similar container which however is small enough to constrain the growth of the plant both below and above ground, thus exerting a dwarfing effect.

Various perforated containers are available from RootMaker (RTM) Products Company of Huntsville, Alabama, USA (www.rootmaker.com), including the Grounder (TM) which is sunk into the ground after planting the plant in the pot. The plant roots can pass through the perforated sidewall but are constrained by the perforations to a maximum diameter of 3/32 inches (2.38mm), so that root branching occurs within the container. The container can subsequently be removed from the ground by breaking off the small roots when the plant is removed from the nursery ready for sale.

US6173531 Bl discloses a container which is used in a similar way to facilitate the removal of the plant from the ground, having peforations 1.5mm in diameter.

Perforated containers may be used to stimulate a healthy root structure which will help the plant to become established when it is moved to its final planting position. However, if the plant is left too long in the same container, the branched root structure will continue to develop until the container becomes congested with roots. At the same time the growing medium will become progressively more structurally degraded and depleted of nutrients, particularly if the container is standing above ground, so that eventually the plant will lose its vigour.

To overcome this problem the plant may be removed and replanted in the ground or in a larger container. Often however this is not possible, for example, when the plant or the container is very large, when there is no room on a patio or balcony for a larger container, or when the plant is growing up a wall. In such cases the conventional practice is to scrape away and replace some of the growing medium at the top of the container. This however can be difficult when the soil is full of roots, and is only of limited effectiveness.

A general object of the present invention is to make it possible to maintain the root structure of a plant in better condition when grown permanently in the same container without repotting.

In a first aspect, the present invention provides a planting system comprising a planting container and at least one root ingrowth container, which may be separate from the planting container or integral with the planting container.

The planting container defines a planting cavity configured to contain the root system of a growing plant while allowing water to drain downwardly out of the planting cavity.

The root ingrowth container includes a perforated wall and defines a root ingrowth cavity which extends from an open, first end of the cavity to an opposite, second end of the cavity. The perforated wall has an external surface, an opposite, internal surface facing the root ingrowth cavity, and a plurality of root ingrowth holes extending from the external surface to the internal surface and opening into the root ingrowth cavity.

In use, the root ingrowth container is arranged alongside a plant growing in the planting cavity. The root ingrowth cavity is filled with a growing medium into which roots of the plant may grow via the root ingrowth holes, with the open end being arranged so that the growing medium can be introduced into the root ingrowth cavity and removed from the root ingrowth cavity via the open end. The perforated wall is arranged to form a barrier to separate the root ingrowth cavity from the planting cavity and to exclude from the root ingrowth cavity any root having a cross-sectional area substantially greater than any of the root ingrowth holes.

In a second aspect, the invention provides a method for planting a plant, wherein the root system of the plant is arranged in the planting cavity of a planting container alongside at least two root ingrowth containers as described above. The planting cavity and the root ingrowth cavities of the root ingrowth containers are filled with a growing medium, so that the roots of the plant may grow through the root ingrowth holes into each of the root ingrowth cavities.

The invention makes it possible, in the use position of the root ingrowth containers and without removing the plant from the planting container, to replace the growing medium in each of the root ingrowth containers in rotation, so that the root system of the plant can continue to grow indefinitely into fresh growing medium to maintain the vigour of the plant. This may be accomplished by:

(a) inserting an extraction tool into the root ingrowth cavity of a respective one of the root ingrowth containers via the respective open end, and operating the tool to extract a body of growing medium and plant roots from the respective root ingrowth cavity, and then (b) refilling the respective root ingrowth cavity via the respective open end with fresh growing medium, and then (c) allowing the root system to regrow into the fresh growing medium within the respective root ingrowth cavity; and then (d) repeating steps (a), (b) and (c) in the root ingrowth cavity of another one of the root ingrowth containers.

In third and fourth aspects of the invention, the or each root ingrowth container as described above has a stiffness and strength sufficient to resist unsupported and substantially without deformation:

a bursting pressure of at least 1.5MPa within each of the root ingrowth holes, and a crushing pressure of at least 1.5MPa over an area A_Cp at each of two portions of the external surface of the perforated wall on opposite sides of the root ingrowth cavity proximate the open end, wherein the area A_Cp is at least 1.0cm².

The resistance to bursting pressure ensures that the perforated wall can resist enlargement of the root ingrowth holes by the turgor of the developing roots and so makes it possible to restrict the size of the roots growing through the root ingrowth holes. This in turn makes it easier in use to cut the roots and extract them from the root ingrowth cavity, and minimises trauma to the plant. The resistance to crushing pressure exerted by plant roots growing externally of the root ingrowth container helps to ensure that the perforated wall will not become inwardly deformed over time by the pressure of plant roots which are trapped between the root ingrowth container and the walls of the planting container or of adjacent root ingrowth containers, and so will not obstruct the operation of an extraction tool inserted into the root ingrowth cavity.

In its third aspect, the invention provides a product range comprising a plurality of root ingrowth containers in at least two different root ingrowth container sizes, defined by a substantially different internal length and/or internal cross-sectional area of the root ingrowth cavity.

In its third aspect, the invention makes it possible to select a number n of root ingrowth containers, preferably at least three or four root ingrowth containers, of a suitable size to be used together alongside a growing plant in the planting cavity of any selected, conventional planting container. This in turn makes it possible to renew in rotation a substantial proportion of the total volume of growing medium in the planting container while cutting away only 1/n of the root system of the plant at any one time.

In its fourth aspect, the invention provides a planting system comprising at least one root ingrowth container and an extraction tool.

In use, the root ingrowth container is received alongside a growing plant in the planting cavity of a selected planting container as described above. The extraction tool is receivable in the root ingrowth cavity via its open end and operable to cut plant roots growing through the root ingrowth holes into a body of growing medium inside the root ingrowth cavity, and to extract the plant roots together with the growing medium via the open end of the root ingrowth cavity.

The extraction tool may comprise a cutting body with at least one cutting edge, and a drive shaft for driving the cutting body in rotation. The cutting body may be configured as an auger to occupy most of the cross-sectional area of the root ingrowth cavity, while the drive shaft may be flexible so that the user can introduce the cutting body into the open end of the root ingrowth container and then operate it by rotating a handle in a convenient position away from the growing plant.

Further features and advantages will become apparent from the various illustrative embodiments of the invention which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:

Figs. 1A - IE show a short, narrow root ingrowth container, and

Figs. 2A - 2E show at the same scale a short, wide root ingrowth container from a range of different sized ceramic root ingrowth containers, wherein:

Figs. 1A and 2A are side views,

Figs. IB and 2B are top views,

Figs. 1C and 2C are bottom views,

Figs. ID and 2D are cross-sections at D - D of Figs. 1A and 2A respectively, and

Figs. IE and 2E are longitudinal sections at E - E of Figs. ID and 2D, respectively;

Figs. 3A and 3B show at the same scale the swept circle described by a rotary extraction tool when operated within the internal section area of the root ingrowth cavity of a root ingrowth container, wherein

Fig. 3A shows a small size tool in a narrow root ingrowth container, and

Fig. 3B shows a large size tool in a wide root ingrowth container;

Fig. 4 shows the range of six different ceramic root ingrowth containers in narrow (short, medium and long) and wide (short, medium and long) sizes, all six sizes being shown at the same scale by way of comparison;

Figs. 5A and 5B show the extraction tool, respectively in a small size for use in the narrow root ingrowth containers, and a large size for use in the wide root ingrowth containers, again at a common scale;

Fig. 6A shows the small extraction tool with the handle and driveshaft casing removed and with the cutting cylinder in longitudinal section;

Fig. 6B shows the driveshaft casing for the small extraction tool;

Fig. 6C corresponds to Fig. 6A but with the driveshaft casing in place;

Fig. 7A is an enlarged view of the cutting head as shown in Fig. 6A;

Fig. 7B is an enlarged view of the cutting head as shown in Fig. 6C, showing the driveshaft connection assembly also in longitudinal section;

Fig. 8 is a side view of the cutting head;

Fig. 9 shows the spiral blade of the cutting head in an initial, flat configuration;

Fig. 10 shows the spiral blade expanded along its rotation axis into its final form;

Fig. 11 shows the cutting cylinder in an initial, flat configuration before it is formed into a cylinder;

Figs. 12A - 12D show the handle, respectively in side view (Fig. 12A), bottom view (Fig. 12B), and end view (Fig. 12C), and sectioned at D - D of Fig. 12C (Fig. 12D);

Fig. 13 shows the handle insert in side and end view;

Fig. 14 shows the handle retaining screw and lock washer;

Fig. 15A and 15B show the handle connection assembly of the flexible driveshaft, respectively in side view and end view;

Fig. 16 shows the handle end of the casing in longitudinal section;

Fig. 17 corresponds to Fig. 12D, showing the handle connected to the flexible driveshaft and the casing;

Fig. 18A and 18B show a planting container, respectively in side and top view;

Fig. 18C shows in top view four root ingrowth containers arranged inside the planting container;

Fig. 18D is a side view of the arrangement of Fig. 18C, with the planting container sectioned at D - D of Fig. 18B;

Fig. 19 shows the arrangement of Fig. 18C after planting a plant between the root ingrowth containers and filling the root ingrowth containers and the planting container with a growing medium;

Fig. 20 is a side view of the arrangement of Fig. 19, with the planting container in longitudinal section, showing how the small extraction tool is inserted into one of the root ingrowth containers after the plant roots have grown through the root ingrowth holes;

Fig. 21 is a partial longtitudinal section through one of the root ingrowth containers of Fig.

showing how the small extraction tool is rotated and then lifted to extract the cut roots and growing medium from the open end of the root ingrowth cavity; and

Fig. 22 shows the root ingrowth container of Fig. 21 after extracting a portion of the growing medium.

Reference numerals and characters appearing in more than one of the drawings indicate the same or corresponding parts in each of them.

Referring to Figs. 1 and 2, each root ingrowth container 20, 21 may consist essentially of a glass or fired ceramic body. For example, it could be made from a glazed or unglazed porcelain, stoneware or other relatively high strength ceramic to help resist root pressure with relatively small wall thickness. Other ceramics may have suitable strength; for example, Pete Pinnell of the University of Nebraska at Lincoln, US has reported that a smooth red earthenware fired to cone 04 and with a well fitted high compression glaze can develop a higher strength than porcelain, (http://www.potters.org/subject47789.htm)

The perforations are formed with a section area suitable to obtain the desired final cross-sectional area after glazing (if glazed), the glaze being applied in any conventional manner to avoid blocking the perforations, for example, as a suspension with suitable rheology or by vapour deposition, e..g. as a salt glaze.

In the illustrated example, each root ingrowth container consists of a unitary ceramic body, fired and glazed. It may be made in one piece, for example by uniaxial pressing, slip casting, or pressure casting. The perforations may be formed during pressing or casting or afterwards, for example, using an array of punches against an internal former such as the male part of a uniaxial press tool. The punches may be hollow and equipped with vacuum or pressure lines to help produce clean holes and to eject the punchings.

As an alternative to one-piece manufacture, the root ingrowth container may be assembled from more than one part before firing it to produce a unitary ceramic body. For example, the tubular wall may be produced by extrusion, in a similar way to the manufacture of clay drainage pipes, using for example an octagonal male former extending from a die fed by a pug mill or other suitable extruder, with a punching station arranged to act against the former to produce the perforations after each length is extruded, following which the perforated length can be cut off and the next length extruded. The base of the root ingrowth container may be produced as a separate component, for example by uniaxial pressing, and then when both parts have reached a suitable moisture content they may be joined together using slip or other suitable adhesive means as well known in the art. The conjoined parts are then fired together to produce a unitary ceramic body.

The root ingrowth container 20, 21 includes a tubular, perforated side wall 3 which defines a root ingrowth cavity 4 which extends along a central length axis XI from an open, first end 5 to an opposite, second end 6. The perforated wall 3 has an external surface 7, an opposite, internal surface 8 facing the root ingrowth cavity, and a plurality of root ingrowth holes 9 extending from the external surface to the internal surface and opening into the root ingrowth cavity.

The lower or second end 6 of the root ingrowth cavity is closed by a base wall 10 of the root ingrowth container, the perforated wall 3 and the base wall 10 together being configured to form a barrier to exclude from the root ingrowth cavity 4 any root 100 having a cross-sectional area substantially greater than any of the root ingrowth holes 9.

A plurality of drainage holes 11 extend through the base wall 10, and a lower wall 12 extends downwardly from the base wall 10 to define a collar surrounding a downwardly open cavity 13 beneath the drainage holes in the use position. In use, the lower wall 12 and downwardly open cavity 13 may help to discourage roots 100 from growing upwardly through the drainage holes 11 and so may help to maintain drainage from the root ingrowth cavity. Preferably each of the drainage holes 11 has a maximum cross-sectional area (i.e. an internal section normal to its length axis) not substantially greater than that of the root ingrowth holes 9.

Advantageously as shown, the root ingrowth cavity may have a polygonal, specifically an octagonal cross-section, with at least some of the root ingrowth holes 9 opening into the root ingrowth cavity 4 proximate vertices 14 of the polygonal cross-section.

Preferably the root ingrowth cavity has a substantially constant cross-section along its length axis between its upper and lower ends 5, 6, so that in use it guides the cutting body 40 of the extraction tool 30, 31 along its entire length. A substantially constant crosssection may be unvarying along the length axis or may include a slight draft angle to facilitate release from a mould, so that the section area Al, A2 reduces very slightly (preferably not more than 10% at most) from the open, first end 5 to the opposite, second end 6.

The root ingrowth cavity 4 is preferably wide enough to contain sufficient growing medium to support a substantial body of roots, without requiring undue force to drive the extraction tool 30, 31 in rotation. Preferably the root ingrowth cavity 4 has a maximum cross-sectional area Al, A2 of not less than 5000 mm² and not more than 25000mm².

In alternative embodiments, the perforated wall may be generally cylindrical to define a root ingrowth cavity of generally circular cross-section, in which case the cutting body 40 of the extraction tool 30, 31 (further described below) may be arranged to occupy most of the cross-sectional area Al, A2 of the cavity 4 and to rotate as it enters the cavity 4 so as to cut through the roots 100 at the point where they pass through the perforated wall

3. This helps the tool to cut through each root cleanly, minimising damage to the roots and minimising the effort required to operate the tool.

A cylindrical root ingrowth container might resemble the perforated jars of the Harappan or Indus Valley Civilisation of the Bronze Age (3300 -1300 BC) which are thought to have been wrapped in cloth and placed in a larger container for use as a strainer.

Alternatively, in order to ensure that, after extracting the roots from the root ingrowth cavity 4, sufficent root remains within the root ingrowth cavity to support regrowth, the extraction tool 30, 31 may be arranged to cut through the roots at a small distance from the inner surface of the perforated wall. This may be achieved by configuring the perforated wall to define guide surfaces to guide the cutting body 40 of the tool in rotation at a distance from the point at which the root ingrowth holes 9 open into the root ingrowth cavity 4.

One way to do this is to provide the root ingrowth cavity 4 with a polygonal crosssection, conveniently defined by a polygonal wall with vertices 14 and flat faces 15 as shown in the illustrated embodiment, wherein the root ingrowth holes 9 open into the root ingrowth cavity 4 proximate the vertices 14 of the polygonal cross-section. The flat faces 15 of the polygon guide the cutting body 40 of the extraction tool in rotation to cut through the roots 100 leaving each root as a short stub 101 projecting from the vertex 14 of the polygon, in which a thin slab of growing medium remains after the tool is withdrawn, and containing the remaining stubs 101 of the roots as shown in Fig. 22 which can then re-grow into the fresh growing medium.

A polygonal external cross-section can also provide a better packing density of the root ingrowth inserts 20, 21 within a planting container 90 so as to increase the proportion of the section area of the planting container which is occupied by the root ingrowth cavities

4. An octagonal cross-section as shown is particularly preferred although hexagonal and other shapes are possible.

Planting containers 90 are decorative as well as functional and vary widely in shape and size. Typically however they tend to be either rectilinear or circular in plan. In order to ensure that the root ingrowth containers 20, 21 can be arranged to occupy a substantial proportion, preferably most of the volume of any selected planting container, it is preferred to provide the root ingrowth containers at the point of sale (e..g. as a physical display in a garden centre or other retail outlet, or as a virtual display on a website) in a range of sizes. Most preferably the root ingrowth containers are provided in a range of lengths and a range of cross-sectional areas (hence widths), so as to suit planting containers which may be deep and narrow, deep and wide, short and narrow, or short and wide.

Preferably therefore a product range (Fig. 4) comprises a plurality of root ingrowth containers 20 - 25, respective ones of said root ingrowth containers defining at least two different root ingrowth container sizes. The root ingrowth cavity 4 of each root ingrowth container 20, 21, 22, 23, 24, 25 has an internal length LI, L2, L3, L4, L5, L6 along its length axis XI between its open end 5 and opposite, second end 6, and an internal cross-sectional area Al, A2 normal to its length axis.

As seen in Fig.4, each of the different root ingrowth container sizes defines a substantially different internal length LI, L2, L3, L4, L5, L6 or internal cross-sectional area Al, A2 or combination thereof. Preferably as shown, respective ones of the root ingrowth container sizes define substantially different internal lengths LI, L2, L3, L4, L5, L6 and respective ones of the root ingrowth container sizes define substantially different internal cross-sectional areas Al, A2, providing the greatest possible flexibility in selecting a root ingrowth container to fit the selected size of planting container.

In the example of Fig. 4, the root ingrowth cavity 4 of each of the narrow root ingrowth containers 20, 22, 24 has an internal section area Al of about 6860mm² and an internal length respectively of LI = 153mm, L3 = 273mm, and L5 = 383mm, while that of the wide root ingrowth containers 21, 23, 25 has an internal section area A2 of about 14000mm²and an internal length respectively of L2 - 200mm, L4 = 320mm, and L6 = 430mm.

Referring to Figs. 18A - 20, the planting container 90 may be of any conventional form, having a side wall 91 and base wall 92 with a drainage hole 93 and defining a planting cavity 94, the planting cavity configured in use to contain a root system 102 of a growing plant 103 while allowing water to drain downwardly out of the planting cavity via the drainage hole 93.

In use, one or more root ingrowth containers are aranged in a use position alongside a plant 103 growing in the planting cavity 94 so that the external surface 7 of each root ingrowth container faces the planting cavity 94. In the illustrated embodiment, each root ingrowth container is separate from the planting container, and preferably two, three, four or more root ingrowth containers are arranged together in the use position, side by side in the planting cavity 94 alongside the growing plant 103.

In the illustrated example, the planting cavity 94 of the selected planting container happens to accommodate three of the medium length narrow root ingrowth containers 22 and one long narrow root ingrowth container 24 which together occupy most of its volume leaving sufficient space for the root system.

The root system 102 of the plant is arranged alongside the root ingrowth containers 22, 24 in the planting cavity 94, externally of the root ingrowth cavities 4, before filling the planting cavity 94 and the root ingrowth cavity 4 of each of the root ingrowth containers 22, 24 with a growing medium 110 such as soil or compost. Typically the base wall 92 of the planting container 90 will be arranged to stand on the ground or on a patio or other hard surface, with the planting container 90 either entirely or at least mostly above ground level. Preferably the upper end 5 of each root ingrowth container is arranged at or just above the level of the growing medium at the top of the planting container, as shown, so that the growing medium 110 may be introduced into the root ingrowth cavity 4 and extracted from the root ingrowth cavity 4 via the open end 5 of the root ingrowth cavity as further described below.

The roots 100 of the plant may then grow via the root ingrowth holes 9 into the growing medium 110 contained in each root ingrowth cavity 4 so that after some time the root ingrowth cavity becomes populated by roots 100. As shown in Fig. 20, the perforated wall 3 is arranged to form a barrier to separate the root ingrowth cavity 4 from the planting cavity 94 and to exclude from the root ingrowth cavity 4 any root 100 having a crosssectional area substantially greater than any of the root ingrowth holes 9.

When the or each root ingrowth container 22, 24 is arranged in its use position, the planting cavity 94 of the planting container 90 will define a residual planting volume V_Pexternally of the root ingrowth containers. Where several root ingrowth containers 22, 24 are arranged entirely inside the planting cavity 94, the residual planting volume V_P will be the total volume of the planting cavity 94, less the combined total external volume of the root ingrowth containers 22, 24.

The combined total internal volume of all of the root ingrowth cavities 4 is defined as a total volume Vc- Desirably, the root ingrowth cavities occupy a substantial proportion of the volume of the planting cavity 94, so that preferably V_c > 0.5 V_P. More preferably V_c 2. V_P. Yet more preferably V_c > 1.5 · V_P.

Referring to Figs. 5A and 5B, each extraction tool 30, 31 comprises a cutting body or cutting head 40, the cutting body having at least one cutting edge 41, 46, and a drive shaft 60 for driving the cutting body in rotation.

As shown in Figs. 20 and 21, the extraction tool 30, 31 is receivable in a use position in the root ingrowth cavity 4 in the use position of the root ingrowth container 22, 24 via the open end 5 of the root ingrowth cavity. The extraction tool is operable to cut plant roots 100 growing through the root ingrowth holes 9 into a body of growing medium 110 inside the root ingrowth cavity, and to extract the plant roots 100 together with the growing medium 110 via the open end 5 of the root ingrowth cavity.

A plurality of extraction tools 30, 31 may be provided as shown, each extraction tool being receivable in the root ingrowth cavity 4 of a root ingrowth container of a respective one of the root ingrowth container sizes. Preferably, the cutting head 40 of each extraction tool 30, 31 is configured to occupy at least most of the cross-sectional area Al, A2 of the respective root ingrowth cavity 4 in the use position of the extraction tool.

Thus, where the root ingrowth container sizes include a first, narrow root ingrowth container size (20, 22, 24) defining a first cross-sectional area Al, and a second, wide root ingrowth container size (21, 23, 25) defining a second, substantially larger cross-sectional area A2, the extraction tools may include a first extraction tool 30 having a first tool width W1 and configured to be received in the root ingrowth cavity 4 of a root ingrowth container 20, 22, 24 of the first, narrow root ingrowth container size, and a second extraction tool 31 having a second tool width W2 substantially greater than the first tool width W1 and configured to be received in the root ingrowth cavity 4 of the root ingrowth containers 21, 23, 25 of the second, wide root ingrowth container size.

Planting containers often have strong, thick walls which are both functional and decorative and can withstand the pressure of growing roots. When one or more root ingrowth containers 22, 24 are arranged in such a planting container to fill most of the volume or plan area of the planting container, the walls of the planting container may react the pressure of expanding plant roots growing between the root ingrowth containers or between the root ingrowth containers and the walls of the planting container, so that, if the perforated wall 3 is insufficiently strong or stiff, it may become deformed inwardly into the root ingrowth cavity 4. For this reason it is preferred for the perforated wall 3 to have a sufficient strength and stiffness to resist the crushing pressure of the plant roots 100 substantially without deformation - which is to say, without deforming to the extent that it would obstruct the normal operation of an extraction tool 30, 31 when the cutting head 40 is inserted into the root ingrowth cavity 4.

The reported values of maximum radial and axial root pressure vary widely. Maximum radial pressure is generally reported as less than 1.5MPa. Misra et al, Maximum axial and radial growth pressures of plant roots, Plant and Soil, October 1986, Volume 95, Issue 3, pp 315-326 (https://link.springer.com/article/10.1007/BF02374612) tabulated a range of values reported in the literature, of which the highest single value was 2.6 MPa. Thus, it seems reasonable to expect that a root confined between opposed surfaces, for example, against the external surface of the perforated wall 3 or in a cylindrical root ingrowth hole 9, will exert a maximum crushing or bursting pressure of probably not more than 1.5MPa, and in any event substantially less than 3MPa (3 N/mm²) against the perforated wall 3 or the wall of the root ingrowth hole 9.

For this reason the root ingrowth container preferably has a stiffness and strength sufficient to resist unsupported (i.e. without relying on other surrounding structure, e..g. the planting container) and substantially without deformation a crushing pressure of at least 1.5MPa over an area A_Cp at each of two portions of the external surface of the perforated wall 3 on opposite sides of the root ingrowth cavity 4 proximate the open end 5, wherein the area A_Cp is at least 1.0cm².

Referring to Figs. 1A and IB, the crushing resistance of a root ingrowth container 20 may be determined by resting the root ingrowth container on a horizontal, square, hard rubber block of area A_Cp, with one side of the block aligned with the upper end 5 of the container as shown in Fig. 1A where the square 120 indicates the footprint of the block. Another block of equal area is arranged on the diametrically opposite side of the root ingrowth container, and a mass selected to apply the crushing pressure is rested on the upper block so that the same crushing pressure is reacted against the lower block, as indicated by the arrows 121 in Fig. IB. As a practical example, for a test pressure of 1.5MPa over an area A_Cp of 1.0cm², a mass of about 15kg is supported on the upper block with the lower block resting on a horizontal support surface. With the pressure applied, the cutting head 40 of the extraction tool may be inserted into the root ingrowth cavity 4 and rotated to check that the root ingrowth cavity 4 is not obstructed.

The area subject to external root pressure will depend on the packing density of the root ingrowth containers and the type and age of the plant, and so the optimal area A_Cp is best determined by trial and error experimentation, as is the thickness of the perforated wall

3. In the illustrated examples the perforated wall of the narrow root ingrowth containers is 7mm thick, and that of the wide root ingrowth containers 10mm thick, but thinner or thicker walls may be used depending on the strength of the material and the selected target crushing pressure. Preferably the area A_Cp is at least 2.5cm², more preferably at least 5.0cm², most preferably at least 7.5cm², to allow for more substantial root systems.

Referring to Figs. 3A and 3B, the swept circle Cl, C2 described by the cutting head 40, respectively of the small extraction tool 30 (Cl) and the large extraction tool 31 (C2), is shown superposed on the internal section area Al, A2 of the root ingowth cavity 4, respectively of the narrow root ingrowth container 20, 22, 24 (Al) and the wide root ingrowth container 21, 23, 25 (A2).

Preferably the cutting head 40 of the extraction tool is arranged to occupy most, more preferably at least about 70%, most preferably at least about 80% of the crosssectional area Al, A2 of the root ingrowth cavity 4, and preferably it is arranged to be operable by rotation about the length axis XI of the root ingrowth cavity 4. For any given axial tool length, a relatively larger proportional section area (hence a tighter fit) helps to support the tool in axial alignment with the root ingrowth cavity 4 and so reduces the force required to operate the tool. Thus, a substantial degree of deformation may be considered as that which would cause the perforated wall 3 to intrude into a nominal cylindrical volume coaxial with the root ingrowth cavity 4 and occupying most, and preferably at least about 80% of its cross-sectional area.

In the illustrated examples, the swept circle Cl, C2 described by the cutting head 40 of each extraction tool 30, 31 as it rotates in operation occupies about 89% to 90% of the internal section area Al, A2 of the root ingrowth cavity 4.

Preferably the cutting head 40 of the tool 30,31 is relatively axially short, preferably less than 60% of the axial length of the root ingrowth cavity 4, so that it is more easily introduced into the root ingrowth cavity 4 beneath the lower branches of the plant 103. In the illustrated example the overall axial length of the cuttting head 40 of the small tool 30 is about 59% of the axial length LI of the root ingrowth cavity of the narrow, short root ingrowth container 20, about 33% of that L3 of the narrow, medium root ingrowth container 22, and about 23% of that L5 of the narrow, long root ingrowth container 24.

Referring to Figs. 5A - 7B, the cutting body or cutting head 40 may be configured as an auger to occupy in use most of the cross-sectional area Al, A2 of the root ingrowth cavity 4, the drive shaft 60 being operable to drive the auger in rotation about the central length axis XI of the root ingrowth cavity 4.

Preferably the drive shaft 60 is flexible so that the user can bend it out of the way of the plant 103 while rotating the handle 80 to drive the cutting head 40 in rotation. The drive shaft 60 may comprise a cable or wire bundle as known in the art, contained in a flexible outer casing 70. The distal end of the drive shaft 60 may be affixed, e.g. brazed into a socket 51 in a leadscrew body 50 on which a leadscrew 52 is formed, e.g. on a screw cutting machine or a CNC lathe with a milling head, or by moulding. The leadscrew body may incorporate a seal, e.g. an O-ring seal 53 which forms a rotating seal with a distal end ferrule 71 of the casing 70 to keep dirt out of the casing.

Referring also to Figs. 8 -11, the cutting body or cutting head 40 may be formed from a flat stainless steel sheet 42 with one long edge contoured to define the cutting edges 41 which face forwardly in the direction of rotation, the short edges being butt welded together at a seam 43 to form the sheet into a cylindrical wall 44. Another flat stainless steel sheet 48 is cut as shown in Fig. 9 to define a leading edge 46 and a central aperture 45 and then pressed in its axial direction to form a helical blade 47 as shown in Fig. 10. The leadscrew body 50 is introduced into the central aperture 45 and welded along the inner edge of the aperture. The radially outward edge of the blade is welded inside the cylindrical wall 44 and the leading edge 46 sharpened to form another cutting edge.

In the design shown, the leading edge 46 curves inwardly and backwardly away from the direction of rotation, and is fixed in the axial direction slightly behind the cutting edges 41 as best seen in Figs. 7A and 7B.

As the cutting head rotates in the direction of the black arrow as shown in Fig. 21, the leadscrew engages the growing medium 110 and draws the cutting head forward. The cutting edges 41 cut through the plant roots first where they enter the root ingrowth cavity, and then the leading edge 46 follows and slices the plug of growing medium and detached plant roots into fragments. If the plant roots resist the cutting action of the leading edge 46 then they are drawn along the leading edge 46 radially inwardly towards the axial centre of the cutting head where there is more torque available to cut them, the cutting edge exerting a slicing action as the roots are drawn along it. Of course, alternative designs are possible.

The helical blade 47 occupies most or all of the plan area inside the cylindrical wall 44 and so by pulling on the handle to draw the cutting head out of the root ingrowth cavity 4 in the direction of the white arrow as shown in Fig. 21, the sliced root fragments and growing medium 110 above the blade 47 are extracted via the open upper end 5.

The tool is assembled by sliding the casing 70 over the hexagonal, proximal end terminal 61 of the drive shaft as shown in Fig. 6C.

Referring to Figs. 12A -17, the handle 80 may be made from wood or plastics material with an insert 81 having a hexagonal socket 82 to transfer torque from the handle to the proximal end terminal 61 of the drive shaft. The terminal 61 has an axial threaded hole 62 to receive a screw 63 with a lock washer 64 which secures it in the insert 81. By removing the screw 63, commercial uses can detach the handle and engage the terminal 61 instead with a power tool for faster operation.

With the root ingrowth containers 22, 24 in the use position as shown in Figs. 19 and 20, after the plant 103 has been in the planting container 90 for a year or more, and without removing the plant 103 from the planting cavity 94, the user inserts the appropriate extraction tool 30 into the root ingrowth cavity 4 of a selected one of the root ingrowth containers 22, 24 via its open end 5 and operates the tool to extract a body of growing medium 110 and plant roots 100 from the root ingrowth cavity 4, as shown in Fig. 21, leaving the remaining root stubs 101 protruding from the root ingrowth holes 9 as shown in Fig. 22.

The user then refills the respective root ingrowth cavity 4 via its open end 5 with fresh growing medium 110, as shown in Fig. 19.

The remaining root ingrowth containers are left alone while the root stubs 101 of the root system regrow into the fresh growing medium 110 within the re-filled root ingrowth cavity 4.

The following year, the user selects another one of the root ingrowth containers 22, 24 and repeats the same steps in its respective root ingrowth cavity 4.

In this way, by providing a number n of root ingrowth cavities 4 alongside a growing plant 103 in one planting container 90, the entire volume of growing medium 110 contained in the root ingrowth cavities 4 may be renewed over a cycle of n years before it becomes structurally degraded, so that the root structure of the plant may grow continuously to extend into fresh growing medium while only 1/n of its root structure is removed at any one time. Thus, a plant 103 may be grown permanently in the same planting container 90 without repotting, and yet may experience a growing environment which allows its root structure to develop continuously in a manner which mimics the continuous outward development of fine roots into fresh ground which would occur in a natural environment.

In use, the user grips the casing 70 to control the position of the cutting head while rotating the handle 80 with the other hand. The perforated wall 3 guides the cutting head 40 of the extraction tool as it enters the root ingrowth cavity 4 while supporting the ingrowing roots 100 at the point where they pass through the perforated wall 3, and so assists the extraction tool 30, 31 to cut through the ingrowing roots 100 as it advances into the cavity 4. The perforated wall 3 also excludes from the root ingrowth cavity plant roots of a section area greater than the root ingrowth holes 9.

By excluding roots of a larger section area than the root ingrowth holes 9 and defining the boundary of the root ingrowth cavity 4, the perforated wall 3 ensures that the larger roots 100 outside the cavity 4 are not damaged when the growing medium 110 is removed from the root ingrowth cavity 4, and further makes it possible to empty and refill each root ingrowth cavity 4 with fresh growing medium 110 in a regular cycle without disturbing the rest of the root structure in the planting container 90.

It is preferred to limit the root ingrowth holes 9 to a section area corresponding to a relatively small root size so as to reduce the effort required to cut through the ingrowing roots 100 within the cavity 4 and to limit damage to the plant when cutting the roots.

Preferably the root ingrowth holes are cylindrical with a circular cross-section, this being assumed for the hole diameters discussed below.

The root ingrowth holes 9 are preferably not less than 0.5mm² in section area or 0.8mm in diameter, and not more than 40mm² in section area or 7.0mm in diameter.

They are preferably sufficiently large to allow plant roots of more than the very smallest sizes to grow into the root ingrowth cavity 4, so preferably at least 1mm², more preferably at least 2mm² in section area, corresponding to a diameter of at least 1.1mm, more preferably at least 1.5mm.

Yet more preferably, the root ingrowth holes should be large enough to permit the ingress of longer lived plant roots of at least about 2mm diameter or 3mm² section area, below which size the roots tend to be ephemeral. Yet more preferably therefore the root ingrowth holes 9 are at least 3mm², yet more preferably at least 4mm², most preferably at least 5mm² in section area, corresponding to a diameter of at least 2.0mm, yet more preferably at least 2.2mm, most preferably at least 2.5mm.

In order to limit damage to the plant and make the roots 100 easier to cut, the root ingrowth holes 9 are preferably not more than 30mm², yet more preferably not more than 20mm², yet more preferably not more than 16mm², yet more preferably not more than 13mm², most preferably not more than 10mm² in section area, corresponding to a maximum diameter preferably not more than 6.0mm, yet more preferably not more than 5.0mm, yet more preferably not more than 4.5mm, yet more preferably not more than 4.0mm, most preferably not more than 3.5mm.

For all these reasons, the section area of the root ingrowth holes 9 is preferably in the range from 2mm² to 13mm², more preferably 3mm² to 10mm², most preferably 4mm² to 10mm , for example, about 7mm as in the illustrated example. This corresponds to a diameter dl (Fig. 1A) preferably in the range from 1.5mm to 4.0mm, more preferably 2.0mm to 3.5mm, most preferably 2.2mm to 3.5mm, for example, about 3mm as in the illustrated example.

Further preferably, the root ingrowth holes 9 are able to resist enlargement due to root turgor so as to restrict the diameter of the ingrowing roots 100, so that the roots 100 can be repeatedly removed with minimal damage to the growing plant. For this reason, the root ingrowth container preferably has a stiffness and strength sufficient to resist substantially without deformation (which is to say, substantially without enlargement of the root ingrowth holes) a bursting pressure of at least 1.5MPa within each of the root ingrowth holes 9.

The resistance to bursting pressure may be calculated using Barlow's formula for the bursting pressure P of a cylindrical pipe:

P = (2-S-T) / OD wherein P = applied pressure and S = material strength.

T is the radial thickness of the wall surrounding the cylindrical root ingrowth hole 9, and so for each hole in an equally spaced array can be taken to be half of the distance between the walls of two adjacent holes along a straight line joining the hole centres.

OD is the outer diameter of the cylindrical wall surrounding the cylindrical hole, and so can be taken as ID+(2-T), wherein ID is the internal diameter of the hole. So

P = (2-S-T) / (ID + (2-T))

DUBBEL - Handbook of Mechanical Engineering - Wolfgang Beitz, Karl-Heinz Kiittner (editors) - Springer-Verlag London Ltd, 1994 quotes a tensile strength for stoneware in the range from 6.5 -13 N/mm².

The tensile strength of porcelain is variously reported as 40 - 50 MPa (https://www.matbase.com/material-categories/ceramics-andglasses/crystalline/traditional-ceramics/material-properties-of-porcelain.html#properties) and as 10.3 -17.2 MPa (https://www.engineeringtoolbox.com/ceramics-propertiesd_1227.html).

By way of example, taking a conservative value of P= 3 N/mm², for a hole with ID=3.5mm and a relatively low material strength S = 6.5 N/mm², the modified formula above yields a value of T= 1.5 mm, suggesting that the radial centres of the root ingrowth holes 9 should be spaced apart by a distance of 6.5mm. The spacing can be reduced of course where the material is of greater strength. It will be noted that the hole spacing is independent of the thickness of the perforated wall 3.

In summary, a plant 103 may be grown permanently in a planting container 90 alongside at least one, preferably three or four root ingrowth containers 22, 24 which occupy a substantial proportion of the volume of the planting container. Each root ingrowth container comprises a root ingrowth cavity 4 and a perforated wall 3 through which plant roots 100 may grow into the root ingrowth cavity. An extraction tool 30 is inserted into the open end 5 of a selected one of the root ingrowth cavities and operated to extract the mass of plant roots 100 and growing medium 110 from the root ingrowth cavity. The root ingrowth cavity is then refilled with fresh growing medium 110 so that the plant roots can re-grow. By refilling the root ingrowth cavities in rotation the soil structure is renewed and the root system of the plant is maintained in a state of continual development.

In alternative embodiments, recesses (not shown) may be formed at the external surface 7 of the root ingrowth container, the recesses extending radially inwardly towards the central axis XI and terminating at one or more root ingrowth holes. The recesses may serve to guide the plant roots to the root ingrowth holes. Each recess may have two or more flat faces which converge radially inwardly to define an included angle along a line which extends to the root ingrowth hole. A plant root travelling along the faces may turn and follow the line to enter the hole.

In alternative embodiments, the body of the root ingrowth container may be formed in a mould from molten glass, or may be moulded from plastics material, epoxy reinforced cement based material, cement, concrete, calcium silicate or other mineral based material, glass reinforced resin, or any other suitable material with suitable corrosion resistance or a corrosion resistant coating. Alternatively the root ingrowth container could be made from a metal, for example, vitreous enamelled steel (optionally, a dual phase vitreous enamel with enhanced toughness) or stainless steel. If made from a metal, the root ingrowth container may be pressed or deep drawn from stainless or weathering steel before or after forming the perforations.

The root ingrowth container may be formed from steel plate in two halves welded together along its length axis and closed at the base with a flat plate with a welded collar. The open end may be reinforced by a solid butt welded steel ring, with the upper edges being shaped to provide a seat for the ring so that the vertices of the polygon extend to its outer meridian and the centre line of each flat face terminates at its inner meridian, with the ring being tack welded at each point along its two meridians. The finished container may be vitreous enamelled. In order to reduce thermal transfer which could chill the plant roots in cold weather, a glass microsphere powder may be applied as an insulative layer, for example, to the hot surface of the vitreous enamel before removing the finished part from the enamelling furnace.

If preferred, the base wall of the root ingrowth container could be formed without a downwardly open collar. The root ingrowth container could also be formed without a base wall, for example, where the tubular side wall will terminate in use at the base of the planting container to prevent roots from entering the open base of the root ingrowth cavity. The root ingrowth container could be formed integrally with the planting container, for example, by forming the perforated wall as a divider connected to an outer wall of the planting container to separate the planting cavity from the root ingrowth cavity. The open end of the root ingrowth container could open via the top of the planting container or at any other convenient position, for example, via an aperture in a side wall of the planting container, optionally having a lid to retain the growing medium inside the root ingrowth cavity, the lid being removable to expose the open end, so that the root ingrowth cavity may extend along a horizontal or inclined axis rather than vertically downwardly as shown in the illustrated embodiments. For example, several root ingrowth containers could be arranged in this way to open through holes in the side walls of a planting container.

The cutting tool could be formed other than as an auger, and if a flexible drive shaft is provided, the drive shaft could be formed as a jointed assembly, and need not have an outer casing.

Many further adaptations are possible within the scope of the claims.

In the claims, reference numerals and characters in parentheses are provided purely for ease of reference and should not be construed as limiting features.

Claims

1. A planting system comprising:

a planting container (90), and at least one root ingrowth container (20, 21, 22, 23, 24, 25);

the planting container defining a planting cavity (94), the planting cavity configured in use to contain a root system of a growing plant (103) while allowing water to drain downwardly out of the planting cavity;

the root ingrowth container including a perforated wall (3) and defining a root ingrowth cavity (4), the root ingrowth cavity extending from an open, first end (5) to an opposite, second end (6), the perforated wall having an external surface (7), an opposite, internal surface (8) facing the root ingrowth cavity, and a plurality of root ingrowth holes (9) extending from the external surface to the internal surface and opening into the root ingrowth cavity;

the root ingrowth container being configured for use in a use position alongside a plant (103) growing in the planting cavity (94), wherein in the use position:

a growing medium (110) may be introduced into the root ingrowth cavity and extracted from the root ingrowth cavity via the open end (5) of the root ingrowth cavity, roots (100) of the plant may grow via the root ingrowth holes (9) into the growing medium (110) contained in the root ingrowth cavity (4), and the perforated wall (3) is arranged to form a barrier to separate the root ingrowth cavity (4) from the planting cavity (94) and to exclude from the root ingrowth cavity any root having a cross-sectional area substantially greater than any of the root ingrowth holes (9).

2. A planting system according to claim 1, wherein the at least one root ingrowth container is separate from the planting container (90) and receivable in the planting cavity (94).

3. A planting system according to claim 1, comprising at least two said root ingrowth containers, the at least two root ingrowth containers being configured or configurable for use together in the use position alongside the plant growing in the planting cavity.

4. A planting system according to claim 3, wherein the at least two root ingrowth containers are separate from the planting container (90) and receivable side by side together in the planting cavity (94).

5. A planting system according to claim 2 or claim 4, wherein the root ingrowth container has a stiffness and strength sufficient to resist unsupported and substantially without deformation:

a bursting pressure of at least 1.5MPa within each of the root ingrowth holes (9), and a crushing pressure of at least 1.5MPa over an area ACp at each of two portions (120, 121) of the external surface (7) of the perforated wall (3) on opposite sides of the root ingrowth cavity (4) proximate the open end (5), wherein the area ACp is at least 1.0cm2.

6. A planting system according to claim 1, including at least one extraction tool (30, 31), the extraction tool being receivable in the root ingrowth cavity (4) in the use position of the root ingrowth container via the open end (5) of the root ingrowth cavity and operable:

to cut plant roots (100) growing through the root ingrowth holes (9) into a body of growing medium (110) inside jzhe root ingrowth cavity (4), and to extract the plant roojts (100) together with the growing medium (110) via the open end (5) of the root ingrowth cavity.

7. A planting system comprising:

at least one root ingrowth container (20, 21, 22, 23, 24, 25), and an extraction tool (30, 31);

the root ingrowth container having a stiffness and strength sufficient to resist unsupported and substantially without deformation:

a bursting pressure of at least 1.5MPa within each of the root ingrowth holes (9), and a crushing pressure of at least 1.5MPa over an area ACp at each of two portions (120,121) of the external surface (7) of the perforated wall (3) on opposite sides of the root ingrowth cavity (4) proximate the open end (5), wherein the area Acp is at least 1.0cm2;

the root ingrowth container being configured for use in a use position alongside a growing plant (103) in a planting cavity (94) of a planting container (90), wherein in the use position:

a growing medium (110) may be introduced into the root ingrowth cavity and extracted from the root ingrowth cavity via the open end (5) of the root ingrowth cavity, roots (100) of the plant may grow via the root ingrowth holes (9) into the growing medium (110) contained in the root ingrowth cavity (4), and the perforated wall (3) is arranged to form a barrier to separate the root ingrowth cavity (4) from the planting cavity (94) and to exclude from the root ingrowth cavity any root having a cross-sectional area substantially greater than any of the root ingrowth holes (9);

the extraction tool (30,31) being receivable in the root ingrowth cavity (4) in the use position of the root ingrowth container via the open end (5) of the root ingrowth cavity and operable:

to cut plant roots (100) growing through the root ingrowth holes (9) into a body of growing medium (110) inside the root ingrowth cavity (4), and to extract the plant roots together with the growing medium via the open end (5) of the root ingrowth cavity.

8. A planting system according to claim 6 or claim 7, wherein the extraction tool (30, 31) comprises a cutting body (40), the cutting body having at least one cutting edge (41, 46), and a drive shaft (60) for driving the cutting body in rotation.

9. A planting system according to claim 8, wherein the cutting body is configured as an auger to occupy in use most of a cross-sectional area (Al, A2) of the root ingrowth cavity (4), the drive shaft (60) being operable to drive the auger in rotation about a central length axis (XI) of the root ingrowth cavity.

10. A planting system according to claim 8 or claim 9, wherein the drive shaft (60) is flexible.

11. A planting system according to any of claims 1 -10, wherein the second end (6) of the root ingrowth cavity is closed by a base wall (10) of the root ingrowth container, the perforated wall (3) and the base wall (10) together being configured to form a barrier to exclude from the root ingrowth cavity (4) any root having a cross-sectional area substantially greater than any of the root ingrowth holes (9).

12. A planting system according to claim 11, wherein a plurality of drainage holes (11) extend through the base wall (10), and a lower wall (12) extends downwardly from the base wall (10) to define a downwardly open cavity (13) beneath the drainage holes (11) in the use position.

13. A planting system according to any of claims 1 -10, wherein the cross-sectional area of each of the root ingrowth holes (9) is from 0.5 mm2 to 40mm2.

14. A planting system according to any of claims 1 -10, wherein the cross-sectional area of each of the root ingrowth holes (9) is from 2mm2 to 13mm2.

15. A planting system according to any of claims 1 -14, wherein the root ingrowth cavity (4) has a polygonal cross-section.

16. A planting system according to claim 15, wherein at least some of the root ingrowth holes (9) open into the root ingrowth cavity (4) proximate vertices (14) of the polygonal cross-section.

17. A planting system according to any preceding claim, wherein the root ingrowth container consists essentially of a glass or fired ceramic body.

18. A product range comprising a plurality of root ingrowth containers (20, 21, 22, 23, 24, 25), respective ones of said root ingrowth containers defining at least two different root ingrowth container sizes;

each root ingrowth container including a perforated wall (3) and defining a root ingrowth cavity (4), the root ingrowth cavity extending along a central length axis (XI) from an open, first end (5) to an opposite, second end (6), the perforated wall (3) having an external surface (7), an opposite, internal surface (8) facing the root ingrowth cavity, and a plurality of root ingrowth holes (9) extending from the external surface to the internal surface and opening into the root ingrowth cavity (4);

each root ingrowth container having a stiffness and strength sufficient to resist unsupported and substantially without deformation:

a bursting pressure of at least 1.5MPa within each of the root ingrowth holes (9) , and a crushing pressure of at least 1.5MPa over an area ACp at each of two portions (120,121) of the external surface (7) of the perforated wall (3) on opposite sides of the root ingrowth cavity (4) proximate the open end (5), wherein the area ACp is at least 1.0cm2;

each root ingrowth container being configured for use in a use position alongside a growing plant (103) in a planting cavity (94) of a planting container (90), wherein in the use position:

a growing medium (110) may be introduced into the root ingrowth cavity (4) and extracted from the root ingrowth cavity via the open end (5) of the root ingrowth cavity, roots (100) of the plant may grow via the root ingrowth holes (9) into the growing medium (110) contained in the root ingrowth cavity (4), and the perforated wall (3) is arranged to form a barrier to separate the root ingrowth cavity (4) from the planting cavity (94) and to exclude from the root ingrowth cavity any root having a cross-sectional area substantially greater than any of the root ingrowth holes (9);

the root ingrowth cavity of each root ingrowth container having an internal length (LI, L2, L3, L4, L5, L6) along its length axis (XI) between its open end (5) and opposite end (6), and an internal cross-sectional area (Al, A2) normal to its length axis (XI);

wherein each of said different root ingrowth container sizes defines a substantially different said internal length or internal cross-sectional area or combination thereof.

19. A product range according to claim 18, wherein respective ones of said root ingrowth container sizes define substantially different said internal lengths, and respective ones of said root ingrowth container sizes define substantially different said internal cross-sectional areas.

20. A product range according to claim 18, further comprising a plurality of extraction tools (30, 31);

each extraction tool being receivable in the root ingrowth cavity (4) of a root ingrowth container of a respective one of the root ingrowth container sizes, in the use position of the root ingrowth container, via the open end (5) of the root ingrowth cavity, and operable in a use position of the extraction tool:

to cut plant roots (100) growing through the root ingrowth holes (9) into a body of growing medium (110) inside the root ingrowth cavity (4), and to extract the plant roots together with the growing medium via the open end (5) of the root ingrowth cavity;

each extraction tool (30, 31) being configured to occupy at least most of said crosssectional area (Al, A2) of the respective root ingrowth cavity (4) in the use position of the extraction tool;

said root ingrowth container sizes including a first root ingrowth container size defining a first said cross-sectional area (Al), and a second root ingrowth container size defining a second, substantially larger said cross-sectional area (A2);

said extraction tools including:

a first extraction tool (30) having a first tool width (Wl) and configured to be received in the root ingrowth cavity (4) of a root ingrowth container of the first root ingrowth container size, and a second extraction tool (31) having a second tool width (W2) substantially greater than the first tool width and configured to be received in the root ingrowth cavity (4) of a root ingrowth container of the second root ingrowth container size.

21. A method for planting a plant (103), comprising:

providing a planting container (90) and at least two root ingrowth containers (22, 24); the planting container (90) defining a planting cavity (94), the planting cavity configured in use to contain a root system (102) of a growing plant while allowing water to drain downwardly out of the planting cavity;

each root ingrowth container including a perforated wall (3) and defining a root ingrowth cavity (4), the root ingrowth cavity extending from an open, first end (5) to an opposite, second end (6), the perforated wall (3) having an external surface (7), an opposite, internal surface (8) facing the root ingrowth cavity, and a plurality of root ingrowth holes (9) extending from the external surface to the internal surface and opening into the root ingrowth cavity (4);

arranging each of the root ingrowth containers (22,24) in a use position wherein:

the external surface (7) faces the planting cavity (94), the perforated wall (3) forms a barrier to separate the root ingrowth cavity (4) from the planting cavity (94) and to exclude from the root ingrowth cavity (4) any root (100) having a cross-sectional area substantially greater than any of the root ingrowth holes (9), and the open end (5) of the root ingrowth cavity is configured to allow a growing medium (110) to be introduced into the root ingrowth cavity (4) and extracted from the root ingrowth cavity via the open end (5);

arranging a root system (102) of the plant (103) alongside the root ingrowth containers (22, 24) in the planting cavity (94) so that roots (100) of the plant may grow through the root ingrowth holes (9) into the root ingrowth cavity (4) of each of the root ingrowth containers (22, 24), and filling the planting cavity (94) and the root ingrowth cavity (4) of each of the root ingrowth containers (22, 24) with a growing medium (110).

22. A method according to claim 21, wherein each root ingrowth container (22, 24) is separable from the planting container (90), and the root ingrowth containers are inserted side by side into the planting cavity (94).

23. A method according to claim 21, further comprising, in the use position of the root ingrowth containers and without removing the plant (103) from the planting cavity (94):

in the root ingrowth cavity (4) of a first one of the root ingrowth containers (22, 24), carrying out steps (a), (b) and (c) comprising:

(a) inserting an extraction tool (30) into the respective root ingrowth cavity (4) via the respective open end (5), and operating the tool to extract a body of growing medium (110) and plant roots (100) from the respective root ingrowth cavity, and then (b) refilling the respective root ingrowth cavity (4) via the respective open end (5) with fresh growing medium (110), and then (c) allowing the root system (102) to regrow into the fresh growing medium (110) within the respective root ingrowth cavity (4); and then (d) repeating steps (a), (b) and (c) in the root ingrowth cavity (4) of a second one of the root ingrowth containers (22, 24).