GB2202722A - Plant restrictor - Google Patents

Abstract

A plant restrictor in the form of a tree ring is used for amenity planting of trees and comprises a tubular upright wall (12) made in glass fibre reinforced cement (grc) in a number of sections boiled together at external flanges (13). Each section is light enough to lift by hand. The plant restrictor has a lid (23) which surrounds a tree to be planted and provides anchorage for supporting the tree (10) and optionally a grille (24) and tree guard (25), as well as levelling up the surface of the planting by use of bearing members (26) and packing strips (27) between the lid (23) and the ring (11). The use of grc provides a strong root containment combined with lightweight for the ring and enables various shapes of restrictor to be readily made. <IMAGE>

Description

TITLE: Plant Restrictor This invention relates to plant restrictors.

Where it is desired to grow large plants in relatively confined spaces, for example in the amenity planting of trees in urban areas, there is a requirement that the spread of roots should be restricted. Unrestricted root growth can lead to damage to underground services such as water or gas pipes, electricity or telephone cables or even to foundations of buildings and roads.

Currently, it is the practice to use a large diameter concrete sewer pipe sunk into the earth with its axis upright, in order to confine the roots of large plants such as trees. However, this practice is unsatisfactory because such a concrete pipe is extremely heavy and requires a crane to place it in position. Additionally, although a concrete sewer pipe is strong in compression, due to its circular cross-section, the expected outward forces of a growing root system within the pipe may eventually induce such a high tensile load in the concrete that the pipe may crack, making it useless for the purpose of restraining the tree roots.

When the concrete pipe has been positioned and the tree planted, finishing work involving a high degree of skill may be required to make good the area immediately surrounding the tree or other plant.

It is an object of the present invention to provide a plant restrictor which overcomes or reduces some or all of these disadvantages.

According to the invention there is provided a plant restrictor having a generally tubular peripheral wall disposed with its axis generally upright in use; the peripheral wall being made wholly or principally of grc (glass fibre reinforced cemement).

Preferably, the generally tubular peripheral wall is open at the bottom in use.

The plant restrictor may have a transverse dimension of greater than 0.5 metres.

The tubular peripheral wall may be an assembly of a plurality of parts. For example it may comprise two parts which may be secured together by bolting.

The tubular peripheral wall may be of generally circular cross-section or of polygonal cross-section, for example rectangular or square.

The tubular peripheral wall may include anchor means adapted to receive anchor ties for supporting a plant upright in the restrictor.

The restrictor may additionally include lid means adapted partially to close the upwardly directed mouth of said tubular peripheral wall. Preferably, the lid means are made wholly or principally of grc.

The lid means may be provided with drainage apertures.

The lid means may have an integral bearing member adapted to rest on the open mouth of the generally tubu lar peripheral wall of the restrictor.

The lid means may be provided with integral fixing means for a grille and/or for a tree guard.

Two plant restrictors in the form of tree rings will now be described in more detail by way of example only with reference to the accompanying drawings in which; FIGURE 1 is a vertical sectional view of a tree ring in use.

FIGURE 2 is a composite plan/sectional view of the tree ring of Figure 1, also illustrating a grille in position with the tree ring.

FIGURE 3 is a detail sectional view of a fixing for the grille.

FIGURE 4 is a vertical sectional view of an alternative embodiment of plant restrictor.

Referring firstly to Figure 1 of the drawings, where it is intended to plant a tree 10 in a relatively confined space where the roots cannot be permitted unrestricted growth, a tree ring plant restrictor generally indicated at 11 is provided. The tree ring 11 has a tubular upright wall 12 which is made as a number of sections 12a for example, which are bolted together by means of externally directed flanges 13. In the example illustrated, the wall 12 has four quarter circular sections 12a but it could equally well be provided in two or three sections, depending on the size and weight of the sections.

Alternatively, the wall could be formed as a single tubular part not requiring further assembly.

In each case; however, the tubular wall 12 is made of glass fibre reinforced cement. This is reinforced with alkali-resistant glass fibre such as the zirconium glass fibre marketed under the registered trade mark CEMFIL by Pilkington Brothers.

Because of the considerable strength imparted to the cement by the glass fibre, a very strong peripheral wall can be made with a very thin cross-section, the strength including tensile strength as well as compressive strength. Thus, compared with a conventional concrete pipe made by conventional spinning or casting into a mould, the grc tubular wall 12 would be of relatively light weight. In the case of a large ring, particularly where this is made in a number of sections as illustrated, each section would be sufficiently light to be moved without the use of a crane, normally necessary for moving a large concrete pipe.

Referring in more detail to Figures 1 and 2 of the drawings, the tubular wall 12 has fixings 14 which are intended to be used for securing guys 15 to hold the tree root ball 16 in position during planting and thereafter.

The wall 12 also has upper and lower flanges 17, 18 to provide increased bearing area.

Each grc section 12a is made by spraying up into a mould in generally known manner. It will be appreciated that the amount and orientation of glass fibre used may be selected to impart the desired strength characteristics to the ring.

In use, the peripheral wall 12 is lowered into a hole, the sections being bolted together as described above. At the foot of the hole, the sub soil would previously have been broken up to assist in drainage. A layer of graded gravel 19 is firstly laid within the peripheral wall. Much of the remainder of the space is then filled with top soil 20, followed by a bed of sand 21 as illustrated. The tree root ball 16 rests on the bed of sand on which it can be firmly bedded down to position the tree. The immediately surrounding area 22 is filled with tree compost to nourish the roots.

However, before the tree is planted, a lid 23 of grc is placed on top of the upright tubular wall 12. The function of this lid is partly to support a conventional cast iron tree grille 24 and optionally a tree guard 25 within which the tree is grown.

Additionally, the lid 23 assists in making good the planting by providing means to level up the tree grille 24 irrespective of any slight problem of positioning the peripheral wall 12. The lid 23 forms an adaptor or connector between the peripheral wall 12 and the tree grille 24, the latter usually being of square shape in cross-section as shown in Figure 2, and formed in two halves, so that it can be placed around the tree after planting.

The grc lid 23 has an integrally formed bearing member 26 of, for example, expanded polystyrene having a grc skin. This bearing member rests either directly on the upper flange 17 of the wall sections 12 or on suitable packing in the form of grc packing strips 27 which can be used to level the lid 23.

A square cross-section opening is provided in the lid 23 to receive the two half grille sections 24. The opening is provided with a suitable stepped shoulder 28 to receive the grille as shown in Figure 1.

The remainder of the lid 23 is positioned at a lower level, below the normal soil level 29. For this reason it is provided with suitable openings 30 for drainage.

In use; the ring sections 12 are firstly positioned and the hole infilled with the materials described. Once the layer of sand 21 has been put down, a coiled perforated pipe 31; having an upwardly directed feed end is positioned around the planting hole and the surrounding area backfilled with graded gravel 32. The lid 23 is then placed in position and packed as necessary using spacers 27 so that the shoulder 28 is levelled; ready to receive the grille 24.

Before placing the grille in position; the tree 10 is planted and the guys 15 are laid, using softwood blocks 33 on top of the root ball to prevent damage. The guys 15 are tightened to hold the tree 10 upright. Op tionally a tree guard 25 is added and bolted at 34 to the lid 23. The outspread limbs 35 of the tree ring 25 can be supported on a further layer 36 of sand to assist in bedding the limbs 35. Finally, the remaining space around the tree is filled with pea gravel 37 for drainage purposes and to prevent the growth of weeds around the tree.

The two halves of the tree grille 24 are positioned around the tree trunk and secured down by bolts 38 as shown in more detail in Figure 3 of the drawings. The area around the tree is levelled and infilled with top soil or paved up to the normal level 29 so that the tree grille is more or less flush with the surface of the ground around the tree.

Figure 3 shows the securing of the tree grille 24 in more detail. The bolts 38 pass through countersunk holes 39 in the grille and are received in threaded sockets 40 which have been cast into the grc lid 23. In order to ensure that the sockets 40 are captive in the lid, cross pins 41 are used for mechanical keying. Figure 3 also clearly shows the shoulder 28 on which the grille 24 rests.

Clearly, the tree ring shown in Figures 1 to 3 is suitable for planting a tree whose roots are expected to spread to a lateral extent greater than the normal size of the tree grille 24. However, trees of lesser dimensions can be planted using a smaller plant restrictor as shown in Figure 4. In this case, the plant restrictor 50 comprises a generally rectangular box of grc which is made in two or more pieces and bolted together on site.

The lid 51 is of a similar rectangular form and is levelled on the main body 50 of the plant restrictor by means of grc spacers 52. In other respects, the planting of the tree proceeds as described above in relation to the first embodiment.

It will be appreciated that plant restrictors can be made in shapes other than square or circular cross sections as required. One advantage of the use of grc is that it is capable of adopting a wide variety of shapes since it is spray deposited on a suitable mould.

Claims (18)

1. A plant restrictor having a generally tubular peripheral wall disposed with its axis generally upright in use; the peripheral wall being made wholly or principally of grc (glass fibre reinforced cemement).

2. A plant restrictor according to Claim 1 wherein the generally tubular peripheral wall is open at the bottom in use.

3. A plant restrictor according to Claim 1 or Claim 2 wherein the transverse dimension of the restrictor is greater than 0.5 metres.

4. A plant restrictor according to any preceding claim wherein the tubular peripheral wall is an assembly of plurality of parts.

5. A plant restrictor according to Claim 4 wherein the tubular peripheral wall comprises two parts secured together by bolting.

6. A plant restrictor according to any preceding claim wherein the tubular peripheral wall is of generally circular cross section.

7. A plant restrictor according to any one of Claims 1 to 5 wherein the tubular peripheral wall is of polygonal cross section.

8. A plant restrictor according to Claim 7 wherein said polygonal cross section is rectangular or square.

9. A plant restrictor according to any preceding claim and including anchor means adapted to receive anchor ties for supporting a plant upright in the restrictor.

10. A plant restrictor according to any preceding claim and additionally including lid means adapted partially to close the upwardly directed mouth of said tubular peripheral wall.

11. A plant restrictor according to Claim 10 wherein said lid means are made wholly or principally of grc.

12. A plant restrictor according to Claim 10 or Claim 11 wherein the lid means are provided provided with drainage apertures.

13. A plant restrictor according to any one of Claims 10 to 12 wherein the lid means have an integral bearing member adapted to rest on the open mouth of said generally tubular peripheral wall of the restrictor.

14. A plant restrictor according to any one of Claims 10 to 13 wherein the lid means are provided with integral fixing means for a grille and/or for a tree guard.

15. A plant restrictor assembly comprising a plant restrictor according to any one of Claims 1 to 14 and a grille fixed thereto.

16. A plant restrictor assembly comprising, in combination, a plant restrictor according to any one of Claims 1 to 14 and a tree guard secured thereto.

17. A plant restrictor substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3 of the drawings.

18. A plant restrictor substantially as hereinbefore described with reference to and as illustrated in Figure 4 of the accompanying drawings.