WO2010052472A1

WO2010052472A1 - Air-pruning apparatus and method

Info

Publication number: WO2010052472A1
Application number: PCT/GB2009/002624
Authority: WO
Inventors: John Newsome Cooley
Original assignee: John Newsome Cooley
Priority date: 2008-11-07
Filing date: 2009-11-06
Publication date: 2010-05-14

Abstract

A plant-propagation tray (2) has a plurality of cells, generally arranged in a regular array such as a rectangular array, for receiving soil or a growing medium for growing plants. At least some cells of the tray have foot-portions (26) such that, in use, when the tray is positioned on a substantially flat or level surface, the foot-portions (26) contact the surface to support the tray (2) such that a lower end of each cell is spaced above the surface, to permit ventilation beneath and around the soil or growing medium contained in each cell. This may advantageously enhance air pruning of roots of plants grown in the soil or growing medium.

Description

Air-Pruning Apparatus and Method

The invention relates to an apparatus and a method for air-pruning, in particular for enhancing air-pruning of the roots of a plant during plant propagation.

When plants are grown commercially in pots or containers, it is desirable to encourage root branching in order to ensure that a plant has a compact vigorous root system devoid of circling roots. This gives the plant a sound basis for its root system to expand and grow when the plant is transplanted from its initial propagation pot or container into a larger container or into the ground. A known method for enhancing such root branching is air-pruning.

When a plant is grown in a container which is not designed for air-pruning, long roots tend to grow without root branching or root division, and tend to circle within the container. An air-pruning container is typically perforated, with a number of openings. When a root tip emerges from such a container through an opening, the intention is that the root tip is killed, and ceases to grow. It is believed that the root tip ceases to grow in the air-pruning process because it has emerged from the compost or other growing media within the container, which is typically moist, into the surrounding air, which is typically less humid. When the root tip emerges into the air it is therefore desiccated and dies. This process is termed air-pruning. When the root tip ceases to grow, root branching or root division from portions of the root which are surrounded by compost within the container is encouraged, and so a more highly branched, compact root system is developed.

However, a problem arises in that the effectiveness of conventional air-pruning methods and apparatus is disadvantageously variable or ineffective. The present invention aims to address this problem.

The invention provides a plant-propagation apparatus, a tray, a container and a method as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the invention are defined in dependent subclaims. In commercial plant-propagation systems, plants are typically grown in individual containers. For convenience in handling large numbers of plants, the containers are arranged in trays, each tray being capable of holding a plurality of containers, such as typically between 20 and 50 containers, or even between 12 and 600 containers. In some cases, trays are handled by hand and in some cases they are handled by automated machinery. In use, the trays are typically arranged on the ground or on benching or tables. The containers used for plant propagation may be air-pruning containers, having perforated sides and/or bases as described above.

As the skilled person is aware, plants may be grown, or propagated, with their roots in any of a number of conventional growing media, such as soil, peat or coir. For convenience in this document these will be referred to by the generic term "compost".

When a plant is grown in a plant-propagation system, compost must be retained around the growing roots of the plant. This can be achieved in several ways. First, loose compost may be retained in a container, typically of plastic; for air-pruning, this must be an air-pruning container. Second, a system such as an Ellepot (RTM) may be used, in which a volume of compost is held in a (typically cylindrical) membrane of a biodegradable material, such as paper. When a plant grows in the compost, the membrane is designed temporarily to retain the compost until the plant's root structure is sufficiently developed to retain the compost itself. Growing roots are not constrained by the membrane. They can grow outwardly through the membrane and if by doing so they emerge into the surrounding air, they may be air-pruned. Third, a system such as a "glueplug" may be used, in which compost is mixed with a polymeric binder and formed into a suitable shape for plant propagation, such as a cylindrical shape or a shape corresponding to a container in which the glueplug will be held. The binder then sets the compost into this shape. As with an Ellepot (RTM), roots can grow out of the glueplug and, if they grow into the surrounding air, can be air-pruned. Other systems include holding compost in a cardboard- like pot, through which roots can grow, and Jiffy (RTM) pots in which compost is held in a net. Compost may therefore either be used as loose compost or retained as a volume of compost in any of a number of known ways. These systems for retaining a volume of compost, such as Ellepots (RTM), glueplugs and the like, will be referred to in this document as "soilholders".

In a plant propagation system in which air pruning is desired, an air-pruning container is advantageously used. For loose compost, an air-pruning container may be used which is designed to retain loose compost but is sufficiently perforated to encourage air pruning. Where a soilholder is used, an air-pruning container may advantageously be used to support the soilholder, but a more extensively perforated container may be used than would be suitable for loose compost. This is because the soilholder may reduce the tendency for compost to fall out of the perforations in the air-pruning container.

When a plurality of plants are propagated in a tray, for ease of handling, the tray may either be designed to receive a corresponding plurality of air-pruning containers, or the air-pruning containers may be integral with cells of the tray in order to receive loose compost, soilholders of compost, or any combination of these systems.

Commonly, when loose compost is used, plants (or seeds or cuttings) may be planted in compost held in a container, and the container positioned in a receiving portion, or cell, of a tray. Alternatively, loose compost may be held in a container integral with a cell of a tray, and a plurality of plants planted directly in the containers integral with the tray. Commonly, when a soilholder of compost is used, a plant (or cutting or seed) may be planted in the soilholder and the soilholder placed in a container which is integral with a cell of a tray. Alternatively, such a soilholder may be placed in a separate air-pruning container and the container positioned in a receiving portion, or cell, of a tray.

In a first aspect, the invention may therefore provide a plant-propagation apparatus comprising an air-pruning container for propagating or growing a plant, and a tray comprising a cell for receiving the container. The cell comprises a foot-portion such that in use, when the tray is positioned on a sufficiently flat or level surface, the foot-portion of the cell contacts the surface to support the tray. When the container is received in the cell, a base, or lower end, of the container is spaced from, or above, the foot-portion of the cell.

In a second aspect, the invention may therefore provide a plant-propagation apparatus comprising an air-pruning container for propagating or growing a plant, the container forming part of, or being integral with, a cell of a tray. The cell comprises a foot-portion such that in use, when the tray is positioned on a sufficiently flat or level surface, the foot-portion of the cell contacts the surface to support the tray. A base, or lower end, of a container portion of the cell is spaced from, or above, the foot-portion of the cell.

In these arrangements, a tray may typically comprise an array of cells, such as 12 or more cells for containing, or forming, a corresponding plurality of air- pruning containers. The array may be a rectangular array. When a tray is filled with a number of containers or plants the spacing between the bases of the containers and the foot-portions of the cells advantageously permits ventilation around and beneath the containers to enhance or enable air-pruning of roots of plants emerging from the containers.

Reference is made to a rectangular array of cells in a tray, and this is an arrangement commonly used in conventional plant-propagation systems, typically using air-pruning containers that are square, round or circular, square with rounded corners, or any other convenient shape. Other arrays of cells may also be used, such as hexagonal arrays. As the skilled person would appreciate, the invention may apply to substantially any cell arrangement or container shape.

In a conventional commercial plant-propagation system, it is desirable to pack plants in their containers closely together, in order to increase the number of plants that can be propagated in a predetermined area of a nursery. Typically, therefore, containers arranged in cells in a tray may be closely packed together. For example, if square containers are used, then they may be packed in cells in a square or rectangular array. In addition, in a nursery, two or more trays are usually positioned adjacent to each other; for example rectangular trays may be positioned adjacent to each other either in a row of trays or in a rectangular array of trays. When two trays are adjacent to each other, they cannot be placed closer to each other than is permitted by the abutment of their rims. However, it is advantageous to be able to position two trays sufficiently close to each other that the cell spacing is not significantly changed, or interrupted, between trays. Such trays may be termed "endless" or "sideless" trays. Ideally, for example, if a tray comprises an array of cells, then the width of the rim of the tray may be half of the width of the upper surface of the tray between two cells in the array, measured in the same direction across the array. In that case, the eel) spacing within the array can be maintained between two adjacent trays. This allows the selected cell spacing for plant propagation to be maintained throughout an array of trays, giving each plant the same growing conditions whether it is in the middle of a tray or at the edge of a tray, and achieving optimal packing of plants so as to make good use of space in a nursery or greenhouse.

Even if the ideal of maintaining an even cell spacing throughout an array of trays cannot be achieved, there is advantage in being able to position adjacent trays such that the spacing between cells at the edges of adjacent trays exceeds the array cell spacing by as little as possible.

In order to achieve good air-pruning, it is important to maintain ventilation beneath the upper surface of a tray and around the air-pruning containers in the cells of the tray. This may advantageously reduce the humidity in the air beneath the tray and encourage air-pruning. This problem is made more difficult when an array of many trays positioned adjacent to each other is considered. Ventilation beneath trays at the centre of an array of trays may be difficult to achieve if the air flow is restricted by the trays nearer the edge of the array of trays. A prior art tray has attempted to improve ventilation beneath containers in the tray by forming a supporting skirt around a portion of the peripheral rim of the tray. The depth of the skirt is greater than the depth of the containers held in the tray and so the tray stands on the lower edge of the skirt, such that the bases of the cells are spaced from the ground or surface on which the tray is supported. This prior art tray has a number of significant disadvantages. First, although the skirt does not encircle the entire periphery of the tray but is formed with several gaps to allow air flow beneath the tray, the skirt impedes air flow and ventilation beneath the tray. The ventilation is impeded even more beneath an array of adjacent trays. Second, the skirt is flared outwards from the rim of the tray towards the bottom of the skirt. This is required so that trays can conveniently nest with one another for storage. However, when two such trays are positioned adjacent to each other, the flared skirts inevitably increase the separation between the trays and therefore interrupt the spacing of the plants growing in the trays. Consequently, the use of a skirt or other structure around the periphery of a tray in order to elevate the cells of the tray above the ground leads to significant disadvantages.

In a preferred embodiment, a tray according to the invention may solve both of these problems by enabling ventilation for all containers in a tray or a group of trays, to encourage good air-pruning, while additionally permitting trays to be placed closely adjacent to each other, unimpeded by supporting structures around the rim of the tray.

In order to obtain adequate ventilation, the inventor has found that the spacing between the base of an air-pruning container and the foot-portion of the cell, or the ground or surface on which the tray is supported, should be at least 15mm, or at least 20mm, 25mm or more, 30mm or more, 40mm or more, or 50mm or more.

In order to encourage ventilation, a cell for receiving a container is advantageously in the form of a frame comprising sufficient structural elements to locate the container and to support the tray while permitting the flow of air for ventilation beneath, and preferably around, the container.

Similarly, when a cell comprises an air-pruning container (the container forming part of, or being integral with, the cell), the foot-portion extends beneath the container-portion of the cell to support the tray, while permitting the flow of air for ventilation preferably beneath and around the container.

The foot-portion of a cell advantageously comprises a load-bearing surface for contacting, in use, a substantially flat or level surface on which the tray is supported. In a tray, all of the cells may comprise a foot-portion but, alternatively, only a fraction of the cells may comprise foot-portions. The purpose of the foot-portions is to support the tray such that the containers are spaced above the surface on which the tray is placed. Depending on factors such as the size of a tray, the number of containers that the tray is to hold, and the size and weight of the compost and plants in the containers, it may be sufficient to provide only a fraction of the cells with foot-portions. For example, in a rectangular array of cells, every other cell might comprise a foot portion, and this may be sufficient to support the tray. In practice, in order to support the entire area of a tray securely and reliably it is anticipated that three or four or more of the cells in a tray, and preferably more than one tenth, or more than one quarter, of the cells in a tray should comprise foot portions. If greater load- bearing capacity is required, then more than one half or more than two-thirds or three-quarters of the cells may comprise foot-portions. The skilled person would appreciate that the number and distribution of foot portions can be varied according to factors such as the size and weight of a tray.

The distribution of the load-bearing foot-portions across the area of the tray is a significant advantage of a tray according to this preferred embodiment of the invention. This is particularly the case when the tray is to be used on the ground, which is desirable in many nurseries, as benching is expensive and inflexible. The surface of the ground, unlike benching, may be uneven and not perfectly level and the distribution of the load-bearing foot portions may then give good mechanical support to the tray without requiring a more expensive, more complex or more bulky tray structure to provide the necessary rigidity and mechanical support for growing plants. Preferably, because of its enhanced design, the tray embodying the invention can then be made as a relatively lightweight, one-piece plastic moulding and still achieve sufficient mechanical performance in use.

In a commercial setting, it is important that trays can be easily handled. In a preferred embodiment, therefore, the cells of a tray embodying the invention are tapered inwardly towards their lower end so that the cells of similar trays may nest within one another and a plurality of trays can therefore be nested together. Advantageously, trays should nest closely together so that a number of nested trays occupies as little overall height as possible. For example, the overall height of 4, 5, 6 or even 7 or more nested trays may advantageously be less than twice the height of a single tray.

In a further preferred embodiment of the invention, the portion of a cell below the base of a container received in that cell continues to taper inwardly. This, combined with appropriate design of the container, advantageously enables a tray to be nested with, and stacked above, a tray that has been filled with containers (where the containers are separate from the tray). Thus, in practice, such trays may be filled with containers and stacked on top of one another prior to loading the containers with plants and compost. This may advantageously enable automated planting of plants in containers, by machine.

Similarly, where the air-pruning containers are integral with cells of the tray, in a preferred embodiment the cells may taper inwardly towards their lower end so that cells of similar trays may nest within one another and a plurality of similar trays can be nested together.

It may be noted that the tapering of containers and cells within the tray, such that the widest part of each container is at its upper end, may advantageously permit ventilation, or airflow, between as well as beneath the containers in a tray. This may advantageously enhance air pruning of roots not only at the base of each container but also enable air-pruning of roots emerging from the sides of containers having perforated side walls. This may advantageously enable air-pruning as high on the root ball as possible.

It is known to allow a gap beneath a plant container to allow for free drainage of water out of the bottom of the container. Typically such gaps are between 1 mm and 5mm. The provision of such small gaps also reflects the desire by manufacturers to use as little material as possible in fabricating components in order to reduce costs. It is also desirable to minimise the overall dimensions of a component such as a tray for receiving plant containers, or a tray in which plant containers are integral, including the height of the tray, because such components are typically fabricated by injection moulding of plastic, and minimising the dimensions of such moulds advantageously reduces costs. Transport costs are also reduced by reducing component sizes. Consequently, it can be seen that increasing the physical dimensions of a tray for plant containers, as in the present invention, goes against normal prejudices in the industry.

Thus, in a preferred embodiment, a tray embodying the invention may consist of a single injection-moulded plastic component, shaped to receive air-pruning containers or having integral air-pruning containers. The containers may be of conventional design or may be modified in order to allow nesting of trays filled with containers, as described above. In some systems, instead of individual air-pruning containers being placed in cells of a tray, a separate tray comprising a plurality of air-pruning containers joined together in an array, may be used. In that case, the plurality of containers may all be inserted into cells of a tray embodying the invention at the same time. This may advantageously simplify handling of the air-pruning containers.

Embodiments of the present invention may therefore provide the following advantages, among others.

a) The frame, or tray, elevates the container or pot above the ground in order to get good air flow and air-pruning.

b) The frame, or tray, has a stronger construction than systems used previously.

c) Because each cell, or a significant proportion of the cells, is extended to the ground there are a number of points of contact with the ground which make this type of frame, or tray, more stable on uneven or wet surfaces.

d) This tray product is a one-piece solution (which may be fabricated as a single moulding) and therefore there is no assembly required. This helps to keep costs down and thus this is a much more economical solution than conventional systems. e) The design is very strong and robust in use.

f) This system is very practical as the trays nest into each other for transport to the nursery thus saving money, as well as for storage taking up less space.

g) The fact that the trays nest also allows them to be automatically de- nested (by machine) for use on the nursery.

h) The frames, or trays, have also been designed in such a way that they will not only nest into other frames or trays but also stack on top of other frames or trays with containers or pots already in them, which makes them even more practical for use on the nursery. Such trays can thus be filled with containers or pots and then stacked, ready for being used on the potting line.

Specific Embodiments and Best Mode of the Invention

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is an isometric cut-away view of a portion of a tray and air-pruning containers according to a first embodiment of the invention;

Figure 2 is an isometric view of a single cell and container embodying the invention;

Figure 3 is a transverse section of the tray of Figure 1 ;

Figures 4, 5 and 6 are different isometric views of the tray of Figure 1 , with the containers removed;

Figures 7, 8 and 9 are different isometric views of a cell of a tray according to a second embodiment of the invention, comprising an integral air-pruning container; Figure 10 is a plan view of the cell of Figures 7 to 9;

Figure 11 is a side view of the cell of Figures 7 to 9;

Figure 12 is a vertical section of the cell as illustrated in Figure 11 ;

Figures 13 and 14 are isometric and vertical-sectional views of the cell of Figures 7 to 12, with a plug of compost in place; and

Figure 15 is an isometric view, from beneath, of a cell according to a further embodiment of the invention.

Figure 1 illustrates a corner of a tray 2 for containing a square array of cells 4. The illustrated portion of the tray contains two parallel rows of four cells. In Figure 1 , the front row of four cells is cut away.

An air-pruning container 6 is received in each cell. Each container is of square cross-section and has an outwardly-extending flange 8 around its upper end, as seen most clearly in Figure 3. The flange sits on a seat 10 at an upper end of each cell. Each container tapers inwardly from its upper end to a base 12. Openings 14 are defined in the base and side walls of each container. When a plant is growing in compost in a container, roots can emerge through these openings for air pruning.

Figure 2 illustrates schematically a single cell of a tray as in Figure 1 , with a container in place. Components in Figure 2 are numbered using the same reference numbers as in Figures 1 and 3.

The tray 2 is illustrated in more detail in Figures 4, 5 and 6. It comprises a peripheral rim 20 around its upper edge, shaped with an inverted-U cross- section for rigidity. Within the rim, a square lattice of beams 22 defines square openings for the containers. The seats 10 are formed along upper edges of the beams for supporting the rims 8 of the containers. Each cell is therefore square in cross-section and comprises a set of four legs 24 extending downwards from corners of the square lattice. The four legs of each cell terminate at their lower end at a foot portion 26, consisting of a substantially square foot with a central square opening. The legs 24 are straight and the cell tapers inwardly towards the foot portion. Each pair of adjacent legs in each cell is also linked by a crossbar 28, slightly beneath the mid-point of the legs, to increase the rigidity of the structure.

In cross-section, each leg has a concave surface facing towards its cell. These inner surfaces on each leg help to guide the container when inserted into the cell.

In the embodiment, each container has an overall height of approximately 100mm and each cell has an overall height of approximately 150mm, so that when a container is inserted into a cell, there is a gap of approximately 50mm between the base 12 of each container and the foot portion 26 of its cell. In addition, because each cell and each container tapers inwardly from its upper end, spaces are left between each adjacent cell and container, for additional circulation of air, or ventilation.

In general, containers and cells may be of various dimensions. A typical range of overall container height may be 25mm to 125mm, and a range of overall cell height may be 50mm to 150mm, so that when a container is inserted into a cell there is a gap of 25mm or more between the base of each container and the foot portion of its cell.

Both the air-pruning containers and the tray are conveniently fabricated by injection moulding, from plastics materials. The tapered form of the containers and the cells is advantageous in this process, as removal of the components from moulds is made easier by the tapered cross-section.

The structure of each cell, as described above and illustrated in the drawings, is in the form of a frame, allowing significant space for air flow and ventilation beneath and around the containers. This advantageously enhances the air- pruning process. The described embodiments use a square array of cells and each cell comprises four legs. The skilled person would appreciate that variations from this are possible within the scope of the invention. For example a hexagonal arrays of cells may be used, each cell then preferably comprising six or three legs. Further, although the legs in the cells of the described embodiments extend along corners of cells, they need not do so. They could extend along sides of cells. Also, the number of legs need not be the same as the number of sides or corners of a cell. A four cornered cell could comprise three or two legs for example.

Figures 7 to 14 illustrate a further embodiment of the invention. Each figure illustrates a single cell of a tray. The complete tray would comprise a square array of cells positioned next to each other, for example in a 6 by 12 array of cells. Since the cells are circular, alternative array patterns, such as a hexagonal array, could be used.

Each cell 50 comprises a circular container portion 52 extending (in use) downwardly from the upper surface 54 of the tray. The container, or container- portion, is an air-pruning container or frame for retaining a soilholder of compost 56, as illustrated in Figures 13 and 14. The air-pruning container comprises an upper rim 58 extending downwardly from the upper surface of the tray 54, and four side-wall portions, or ribs, 60 extending downwardly from the rim 58 to a container base 62. The rim and the side-wall portions taper inwardly towards the base and the side-wall portions are positioned at 90° intervals around the circumference of the container. The base is of cruciform shape, linking the lower ends of the side-wall portions, and has a central circular opening 64.

The container-portion 52 is thus adapted to receive a soilholder of compost 56. If the soilholder is cylindrical, then it is preferably of a suitable size such that it is a close fit at the base of the tapered container, but it can be a looser fit at the top of the tapered container, as illustrated in Figure 14.

The gaps between the side-wall portions 60, the gaps between the four arms of the cruciform-shaped base, and the central opening in the cruciform base all provide air-pruning openings for air pruning of any roots that grow out of the soilholder and emerge in an air-pruning opening. The container-portion of the cell thus serves as an air-pruning container for the soilholder.

Four legs 66 extend downwardly from the base of the container, to foot portions 68. As described in relation to the first embodiment, the foot portions serve to support the tray and ensure adequate space beneath the base of the container portion of each cell such that air flow around the compost held in the container portions can lead to effective air pruning.

Figure 15 illustrates a further embodiment, comprising a container portion as in Figures 7 to 14, but comprising only two legs and foot portions extending from the base of the container. The specific structure and number of the foot portions in a tray may be determined by the skilled person in view of a number of factors including the following; the size of the tray and the number of cells in the tray, the weight of the compost and plants to be held by the tray, and the proportion of the cells which are provided with foot portions, and the distribution of those cells within the tray.

As can be seen from the drawings in Figures 7 to 15, the container portions and foot portions of the cell are both tapered and are constructed such that cells in similar trays can nest within each other, so that similar trays can be nested. In the embodiments of Figures 7 to 15, the tray height is 70mm, and similar trays can nest such that the spacing between adjacent trays is only about 10mm.

Claims

1. A plant-propagation tray comprising a cell having a foot-portion such that in use, when the tray is positioned on a substantially flat or level surface, the foot-portion of the cell contacts the surface to support the tray;

and in which, when an air-pruning container is in position in the cell, a base or lower end of the container is spaced from the foot-portion of the cell.

2. A plant-propagation tray according to claim 1 , in which the base of the air-pruning container is spaced from the foot-portion of the cell so as to permit ventilation around and beneath the container to enable air pruning of roots of the plant emerging from the container.

3. A plant-propagation tray according to claim 1 or 2, in which the base of the container is spaced from the foot-portion of the cell by more than 15mm, 20mm, 25mm, 30mm, 40mm or 50mm.

4. A plant-propagation tray according to claim 1 , 2 or 3, in which the cell is adapted to receive a separate air-pruning container while permitting ventilation around and beneath the container.

5. A plant-propagation tray according to claim 4, in which the air-pruning container is a container for loose compost or for a soilholder of compost.

6. A plant-propagation tray according to any of claims 1 to 3, in which the air-pruning container is integral with, or forms part of, the cell.

7. A plant-propagation tray according to claim 6, in which the air-pruning container is a container for loose compost or for a soilholder of compost.

8. A plant-propagation tray according to any preceding claim, in which the foot-portion of the cell comprises a load-bearing surface for contacting, in use, a substantially flat or level surface on which the tray is supported.

9. A plant-propagation tray according to any preceding claim, in which the tray comprises a plurality of cells, at least a fraction of the plurality of cells comprising foot-portions, the foot-portions of the fraction of the cells being sufficient to support the tray, in use.

10. A plant-propagation tray according to claim 9, in which the cells comprising foot-portions are distributed substantially evenly among the cells in the tray.

11. A plant-propagation tray according to claim 9 or 10, in which more than one quarter, preferably more than one half and particularly preferably more than two-thirds of the cells comprise foot-portions.

12. A plant-propagation tray according to any of claims 1 to 9, in which each cell comprises a foot-portion.

13. A plant-propagation tray according to any preceding claim, in which a first tray can be nested in a second similar tray to form a stack of trays.

14. A plant-propagation tray according to claim 4 or 5, in which containers can be received in cells of a first tray and a second similar tray can be nested in the containers in the first tray, foot portions of cells of the second tray being located in the containers.

15. A plant-propagation apparatus comprising a tray and a separate air- pruning container as defined in claim 4 or 5.

16. A container for a plant-propagation apparatus as defined in claim 15.

17. A method for plant propagation, comprising the steps of;

locating an air-pruning container in a cell of a tray such that a base of the container is spaced from a supporting foot-portion of the cell, so as to provide sufficient ventilation beneath and around the container to enable air pruning of roots of a plant contained in the container.

18. A method according to claim 17, in which the air-pruning container is a separate air-pruning container to be received in the cell.

19. A method according to claim 17, in which the air-pruning container is integral with, or forms part of, the cell.

20. A plant-propagation apparatus comprising:

an air-pruning container for receiving a plant, the container having a base; and

a tray comprising a cell for receiving the container, the cell comprising a foot-portion such that in use, when the tray is positioned on a substantially flat or level surface, the foot-portion of the cell contacts the surface to support the tray;

in which the base of the container is spaced from the foot-portion of the cell when the container is received in the cell.

21. A plant-propagation apparatus according to claim 20, in which the base of the air-pruning container is spaced from the foot-portion of the cell so as to permit ventilation around and beneath the container to enable air pruning of roots of the plant emerging from the container.

22. A plant-propagation apparatus according to claim 20 or 21 , in which the base of the container is spaced from the foot-portion of the cell by

15mm or more, preferably by 30mm or more, and particularly preferably by 50mm or more.

23. A plant-propagation apparatus according to claim 20, 21 or 22, in which the cell is in the form of a frame for receiving the container while permitting ventilation around and beneath the container.

24. A plant-propagation apparatus according to any of claims 20 to 23, in which the foot-portion of the cell comprises a load-bearing surface for contacting, in use, a substantially flat or level surface on which the tray is supported.

25. A plant-propagation apparatus according to any of claims 20 to 24, in which the tray comprises a plurality of cells for receiving a corresponding plurality of containers, at least a fraction of the plurality of cells comprising foot-portions, the foot-portions of the fraction of the cells being sufficient to support the tray, in use.

26. A plant-propagation apparatus according to claim 25, in which the cells comprising foot-portions are distributed substantially evenly among the cells in the tray.

27. A plant-propagation apparatus according to claims 25 or 26, in which more than one quarter, preferably more than one half and particularly preferably more than two-thirds of the cells comprise foot-portions.

28. A plant-propagation apparatus according to any of claims 20 to 25, in which each cell comprises a foot-portion.

29. A plant-propagation apparatus according to any of claims 20 to 28, in which a first tray can be nested in a second similar tray to form a stack of trays.

30. A plant-propagation apparatus according to any of claims 20 to 29, in which containers can be received in cells of a first tray and a second similar tray can be stacked on the containers in the first tray, foot portions of cells of the second tray being located in the containers.

31. A tray for a plant-propagation apparatus as defined in any of claims 20 to 30.

32. An air-pruning container for a plant-propagation apparatus as defined in any of claims 20 to 30.

33. A tray substantially as described herein with reference to the drawings.

34. An air-pruning container substantially as described herein with reference to the drawings.

35. A method for plant propagation substantially as described herein with reference to the drawings.