Plant-growing tray

Abstract

A plant-growing tray for containing cylindrical stabilised media for growing plants comprises an array of flared columns, a lower end of the columns being wider than an upper end. The columns define an array of cells therebetween for containing cylindrical stabilised media, and a column comprises one or more contact edges defined by an intersection between a wall of the flared column and a virtual cylindrical surface in a cell, such that the contact edges are suitable for contacting a cylindrical stabilised medium positioned in the cell.

Claims

1. A plant-growing tray for containing cylindrical stabilised media for growing plants, the tray comprising: an array of flared columns, a lower end of the columns being wider than an upper end; in which the columns define an array of cells therebetween for containing cylindrical stabilised media; and in which a column comprises an arch-shaped contact edge defined by an intersection between a wall of the flared column and a virtual cylindrical surface in a cell, such that the contact edges are suitable for contacting a cylindrical stabilised medium positioned in the cell.

2. A plant-growing tray according to claim 1, in which one or more flared columns are open-ended chimneys defining passages through which air may flow.

3. A plant-growing tray according to claim 2, in which the arch-shaped contact edge extends upwardly over the column, and in which the width of the arch-shaped contact edge widens towards the lower end of the column.

4. A plant-growing tray according to claim 1, in which the column comprises a concave portion below the arch-shaped contact edge, optionally in which the concave portion has a curvature equal to that of the virtual cylindrical surface.

5. A plant-growing tray according to claim 1, in which the contact edge extends upwardly over at least 40% 50%, or 60%, or 70%, or 80%, or 90% of the height of the column, optionally over the entire height of the column.

6. A plant-growing tray according to claim 1, in which one or more columns is hollow and comprises one or more openings through the wall of the column, the edges of the openings being configured to lie on the virtual cylindrical surface in the cell, optionally in which the edge of an opening forms a contact edge for contacting a cylindrical stabilised medium positioned in the cell.

7. A plant-growing tray according to claim 6, in which the column comprises one or more arch-shaped openings through its wall, and in which the arch-shaped openings widen towards the lower end of the column and/or in which the one or more openings are positioned between two contact edges on the same column wall, optionally in which the opening spans the distance between two contact edges; and/or in which the one or more openings are formed through a vertex of the column.

8. A plant-growing tray according to claim 6, in which a wall of the column defines a cell side wall and comprises an opening, and in which the area of the opening occupies less than 75% of the area of the column wall, or less than 50%, or 40%, or 30%, or 20%, or 10% of the area of the column wall; and/or in which the openings in the columns extend upwardly from a cell base over a portion of the column that is greater than an equal to 25%, or 30%, or 40% of the height of the columns, and less than or equal to 45%, or 50%, or 60%, of the height of the columns.

9. A plant-growing tray according to claim 1, in which the flared columns comprise a circular cross-section, or a square cross section, or a polygonal cross section.

10. A plant-growing tray according to claim 1, in which the columns comprise a plurality of convex walls configured to form cell walls, or in which the columns comprise a plurality of flat walls configured to form cell walls.

11. A plant-growing tray according to claim 1, in which the two sides of the arch-shaped contact edge form two contact edges positioned on column walls either side of a vertex of the flared column, and in which the portion of the vertex between the contact edges is configured to define an intersection between the walls of the flared column and a virtual cylindrical surface in a cell.

12. A plant-growing tray according to claim 1, in which an upper portion of the flared columns is chamfered, such that the chamfered columns define a widened upper portion of the cells, optionally in which the chamfered upper portions of the columns extend over greater than or equal to 5%, or 10%, or 15%, and less than or equal to 18%, or 20%, or 25%, of the height of the columns.

13. A plant-growing tray according to claim 1, comprising a plurality of column-connecting walls configured to connect adjacent columns to one another.

14. A plant-growing tray according to claim 13, in which the column-connecting walls are configured to connect the upper ends of adjacent columns to one another, such that the column-connecting walls form a tray top on top of which a similar tray may be stacked; or in which the lower ends of the flared columns are hollow and the column-connecting walls are configured to connect the lower ends of adjacent columns to one another and to extend upwardly from the lower end over a portion of the column that is greater than or equal to 10%, or 20%, or 30% of the height of the columns, and less than or equal to 40%, or 50%, or 60% of the height of the columns, such that the upper ends of the flared columns may be nested underneath the flared columns of a similar try.

15. A plant-growing tray according to claim 1, in which the flared columns have an angle of taper which varies along their height.

16. A plant-growing tray according to claim 1, comprising one or more projections facing into the cell, configured in use to contact the cylindrical stabilised medium positioned in the cell; optionally in which the projections are configured in use to contact an upper portion of the stabilised medium; and/or in which at least a portion of the projections is configured to contact the cylindrical medium at a greater height than the one or more contact edges; and/or in which the projections comprise vertical ribs.

Description

DESCRIPTION OF SPECIFIC EMBODIMENTS AND BEST MODE OF THE INVENTION

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

(2) FIGS. 1a and 1b are perspective views, from above, of a section of a first plant tray according to the prior art;

(3) FIG. 2a is a perspective view of a second plant tray according to the prior art;

(4) FIG. 2b is a perspective view of the prior art plant tray of FIG. 2a, containing several cylindrical stabilised media;

(5) FIG. 3a is a perspective view, from above, of a section of a plant tray according to a first preferred embodiment of the present invention;

(6) FIG. 3b is a plan view of the tray of FIG. 3a;

(7) FIG. 3c is a perspective view of the underside of the plant tray in FIGS. 3a and 3b;

(8) FIG. 3d is a perspective view, from below, of the plant tray in FIGS. 3a to 3c when containing a plurality of stabilised media;

(9) FIG. 3e is a perspective view, from above, of a larger section of the plant tray of FIGS. 3a to 3d;

(10) FIG. 4a is a perspective view, from above, of a single cell of a plant tray according to a second preferred embodiment of the present invention;

(11) FIG. 4b is a cross-sectional view, taken along the line X-X, of the cell of FIG. 4a;

(12) FIG. 4c is a cross-sectional view, taken horizontally through the cell of FIG. 4a at 50% of the opening height;

(13) FIG. 4d is a cross-sectional view, taken horizontally through the cell of FIG. 4a above the opening;

(14) FIG. 5a is a perspective view, from above, of a section of a plant tray according to a third preferred embodiment of the invention;

(15) FIG. 5b is a perspective view, from almost vertically above the plant tray of FIG. 5a;

(16) FIG. 5c is a perspective view of the underside of the plant tray in FIGS. 5a and 5b;

(17) FIG. 5d is a perspective view from almost vertically below the plant tray of FIG. 5a to 5c;

(18) FIG. 6a is a perspective view, from above, of a corner section of a plant-growing tray according to a fourth preferred embodiment of the present invention;

(19) FIG. 6b is a cross-sectional view, taken along the line A-A, of the plant-growing-tray of FIG. 6a;

(20) FIG. 6c is a plan view of the section of plant-growing-tray of FIGS. 6a and 6b;

(21) FIG. 7a is a perspective view, from above, of a section of a plant-growing tray according to a fifth preferred embodiment of the present invention;

(22) FIG. 7b is a plan view of the section of plant-growing-tray of FIG. 7a;

(23) FIGS. 8 and 9 are perspective views of a plant-growing tray according to a sixth preferred embodiment of the invention; and

(24) FIG. 10 is a perspective view of a cell of a plant-growing tray according to a seventh preferred embodiment of the invention.

(25) FIGS. 1a and 1b illustrate a repeat section of a prior art plant tray 2, which is marketed by Proptek® as model no. 126S58I: 126 Cell Stacking Eucalyptus & Forestry Propagation Tray. The illustrated section of prior art tray comprises a square, 2 by 2, array of square cells 4. Each cell is defined by a cell-base 6, formed by a grid of parallel base-ribs spanning a bottom end of the tray, and four pairs of support ribs 8 projecting into the cell. Individual pairs of ribs 8 are connected to one another by vertical cell side-walls 10. Tray-top ribs 12 connect separate cell side-walls to one another at the top of the tray. Between side walls 10 the corners of the cells are open, so that air may flow freely between the cells and around stabilised media positioned in the tray.

(26) Support ribs 8 are arranged to extend vertically from the cell-base, so that when a cylindrical stabilised medium (not shown) is inserted into a cell, its bottom end rests on the cell-base 6, and the support ribs 8 contact the sides of the stabilised medium so as to hold it upright in the cell.

(27) FIGS. 1a and 1b show a four-cell unit bounded by dividing wall 14, which extends vertically from the cell base to the tray top. The 126S58I commercial embodiment of the tray, however, comprises 126 cells in a 9×14 array, in which the boundary wall is formed only around the outermost edge of the 9×14 array.

(28) FIGS. 2a and 2b show a section of a different prior art plant tray 20, which is marketed by Proptek® as model no. 126N58N: 126 Cell Nesting Eucalyptus & Forestry Propagation Tray.

(29) The 126N58N prior art tray 20 comprises a regular array of cells 22, each of which is defined by a cell-base 26 formed by a grid of base-ribs, and a cell wall 28 which projects upwards approximately 10 mm above the cell base 26 and extends around the sides of the square cells. Each cell 22 comprises four pairs of ribs which project upwards from the cell-base, and converge to connect to one another and form an inverted “V” shaped rib 30 over the corner of the cell. Some inverted V ribs 30 are connected to the inverted V rib of an adjacent cell by a connecting member at their uppermost end. Inverted V ribs 30 which are not connected to an adjacent rib 30 are supported by a third upright rib which extends upwards from the corner of the cell to form a tripod with the inverted V shaped rib 30.

(30) Large openings under the upright ribs allow the tray 20 to be nested with a similar tray, the uprights of which can be nested underneath and inside the inverted V ribs of the tray above.

(31) As shown in FIG. 2b, in use, stabilised media 23 such as Ellepots® are inserted into the cells 22 between the inverted V shaped ribs at the corners of the cells. When the stabilised media are in position within the cells, the inverted V ribs 30 abut the sides of the stabilised media to hold them in place. The inverted V ribs 30 and the cell base 26 are very thin, so that the area of plastic tray in contact with each stabilised medium is very small, and as much of the stabilised medium as possible is exposed to airflow for air pruning.

(32) FIG. 3a to 3e illustrate a plant tray 40 according to a first preferred embodiment of the present invention.

(33) The tray 40 is formed from hollow columns, or chimneys, 42 arranged in a regular square array, so that the spaces left between adjacent columns 42 form a regular array of cells 44. Each column 42 is shared between four cells, so that each quarter of the column effectively protrudes into the corner of a different cell.

(34) The columns 42 are flared in shape, with their bases wider than their tops, and four inclined convex walls 46 arranged in a roughly diamond shape relative to the array of cells, so that each convex column wall 46 forms a cell wall of a different cell. The columns are hollow, and open-ended, so that air may flow upwards or downwards through the columns without passing through a cell.

(35) Base ribs 48 extend between the bases of neighbouring column walls 46 in a grid that defines the cell-base.

(36) An upper portion 52 of the column walls is chamfered to widen the cell opening through which stabilised media are inserted into and removed from the cell, in order to make placement of stabilised media easier, particularly for automated systems. The chamfered upper portion 52 is rounded in both horizontal and vertical planes, in order to provide a smooth surface for guiding-in stabilised media to the cells.

(37) Column-connecting walls 50 span the gap between adjacent columns 42, and extend from the base to the upper end of the columns, so that the top surface of the column-connecting walls forms a tray top.

(38) Cross-bars 56 are positioned inside the hollow columns 42 and span the open upper ends of the columns to provide improved strength and rigidity.

(39) Pairs of two contact edges 57 are formed on each column wall by a change in angle of the column wall. The two contact edges 57 are arranged either side of, and define, the intersection between the inclined column wall and a virtual cylindrical surface in the cell.

(40) The pairs of contact edges 57 are separated by an angular distance of 40 degrees of the circumference of the virtual cylindrical surface.

(41) Concave portions 58 are formed in each of the convex column walls 46 between pairs of contact edges 57, so that the concave portions span the space between the contact edges and lie on the virtual cylindrical surface.

(42) The contact edges 57 and the concave portions 58 extend over the column walls over the entire height of the columns, from the cell base to the upper end of the columns.

(43) Below the chamfered upper portion 52 of the columns, the contact edges and concave portions of all four columns around a cell 44 lie on the same virtual cylindrical surface. Thus, when a cylindrical stabilised medium of appropriate dimensions is inserted into the cell, the outer walls of the stabilised medium will contact the concave portions of the columns.

(44) As the column walls 46 are inclined, or tapered, the separation of opposing columns is smaller at the cell base than it is at the cell top. The concave portions 58 therefore become gradually wider and deeper towards the base of the column wall, so that the concave portion still lies on the cylindrical surface as the column separation narrows.

(45) In the preferred embodiment shown in FIGS. 3a-3d, the lower, non-chamfered portion of the convex column walls 46 has a draft angle of 1.25 degrees from vertical. While a non-zero draft angle is required for injection moulding, the concave portions 58 have a draft angle of 0.25 degrees to lie as closely as possible on the virtual cylindrical surface in the cell. The draft angle of the chamfered upper portion 52 of the columns is 26 degrees.

(46) Each column wall 46 comprises an opening 54 in the concave portion. The openings 54 take the form of arch-shaped cut-outs in the column walls 46, starting at the column base and extending upwards from the base over approximately 45% of the column height. The openings 54 are widest at the column base, where they span an angular distance of 26 degrees of the column circumference, and gradually narrow as they extend upwards. As they are formed in the concave portions 58, the edges of the openings 54 lie on the same cylindrical surface as the concave portions. The edges of the openings 54 thus form contact edges defining an intersection between the wall of the flared column and the virtual cylindrical surface in the cell.

(47) The size and shape of the openings 54 are selected so that the area of the opening in the column wall 46 is equivalent to roughly 9% of the total area of one of the column walls facing into the cell (opening surface area 178 mm.sup.2; total surface area of one of the column walls facing into the cell 2048 mm.sup.2). This opening is therefore significantly smaller than the apertures provided in the skeletal prior art trays, in which 60-80% of the cell sides are open.

(48) Suitable cylindrical stabilised media are chosen to have an outer diameter approximately equal to the diameter of the virtual cylindrical surface defined by the concave portions 58.

(49) One such suitable stabilised medium may be Ellepots® with a diameter of 30 mm. However, the skilled person will appreciate that trays may be provided to accommodate stabilised media of various heights and diameters by altering the heights and separation of columns in the array. Cylindrical stabilised media are typically available from 23 mm wide and from 30 to 60 mm tall. The biggest cylindrical medium currently available is 120 mm wide by up to 12 inches tall. For forestry applications, stabilised media are typically at least 30 mm wide and from 70 mm to 100 mm high, while the largest currently available is 40 mm wide and from 80 to 120 mm tall.

(50) In use, cylindrical stabilised media 60 are inserted into the cells 44 so that the bottom ends of the stabilised media abut the base ribs 48 of the cell base 50, as shown in FIG. 3d. In this position, the cylindrical sides of the stabilised media are in contact with the column wall along the contact edges 57, over the concave portions 58 of each column wall 46 and along the arch-shaped edges of the openings 54. The contact area between a cylindrical stabilised medium 60 and a column wall 46 is therefore roughly shaped like an inverted “Y”. When in position, portions of the lower end of the stabilised media protrude through the openings 54 into the interior of the hollow columns 42.

(51) Unlike the trays of the prior art, the columns and the column-connecting walls of the plant tray prevent the free flow of air between cells. While this was previously thought to be disadvantageous, as it may reduce air pruning, the design of the present tray has been found to improve irrigation management by reducing the rate at which water is evaporated from the stabilised media. The columns also greatly reduce the problem of root bridging between neighbouring cells. The columns are also much more physically robust than the upstanding skeletal ribs of the prior art tray in FIGS. 2a and 2b, which is important for the lifespan of the reusable tray.

(52) As shown in FIG. 3d, the stabilised media do not occlude the entire base of each cell, so some air may flow upwards or downwards past the stabilised media. Air flowing through the columns and below the cell base may also flow over the exposed portions of the stabilised media to promote air pruning. By preventing free flow of air laterally through the tray between cells, however, irrigation management and root bridging have been improved while still obtaining satisfactory air pruning.

(53) FIG. 3e shows a 4×8 square array of the cells described above in relation to FIGS. 3a-3d, bounded on two sides by a tray wall 62 which spans the entire height of the tray from the base to the tops of the columns. As the skilled person will appreciate, the tray of the present invention may be adapted to comprise a desired number of cells by varying the size of the array of columns. A preferred tray size may be, for example, 98 or 126 cells.

(54) FIG. 4a-4d illustrate a single cell 100 of a plant tray according to a second preferred embodiment of the present invention. The cell 100 is similar to the cells 44 of the plant tray 40. Instead of two contact edges extending over the entire height of the columns, however, the cell 100 is bounded by inclined column walls 120 which each have an arch-shaped contact edge 130 defining an intersection of the column walls 120 with a virtual cylindrical surface with a diameter of 30 mm in the cell. The arch-shaped edge extends from the cell base upwardly over approximately 85% of the height of the column, with its apex positioned just below a change in the draft angle of the column wall to form an upper chamfered portion 135.

(55) Below the arch-shaped contact edge 130, the arch is spanned by a concave portion 140 which lies on the virtual cylindrical surface. A roughly triangular opening 150 is formed through each column wall in the concave portion 140.

(56) As shown in FIG. 4b, when a cylindrical stabilised medium 145 with a height of 100 mm and a diameter of 30 mm (the same as the virtual cylindrical surface) is positioned in the cell 100, the stabilised medium contacts the column walls 120 along the contact edge 130 and over the surface of the concave portion 140, as indicated by the shaded area in FIG. 4. Lower portions of the stabilised medium project outwards through the openings 150 into the interior of the hollow columns, and the stabilised medium is contacted and supported upright by the column walls.

(57) As shown in FIGS. 4c and 4d, the cylindrical stabilised medium 145 is in contact with the column walls 120 within the arch-shaped contact edge 130 and over the concave portion 140.

(58) In FIGS. 4c and 4d:

(59) X=Interference between Stabilised medium and cell sides;

(60) Y=0.02 mm clearance between Stabilised medium and cell sides.

(61) The 0.25 degree draft angle of the concave portion 140 may create a very small gap (for example, around 0.24 mm) between the surface of the stabilised medium and the column wall at the bottom of the chamfered portion. Manufacturing tolerances of stabilised media, and swelling of stabilised media when watered, however, will mean that the stabilised media contacts the column walls over the contact edges and the concave portion.

(62) FIGS. 5a-5d illustrate a plant tray 70 according to a third preferred embodiment of the invention.

(63) The plant tray 70 of FIGS. 5a-5d is similar to the embodiment of FIGS. 4a-4e, except that the frusto-conical columns of FIGS. 4a-4e are replaced with an array of flared frusto-pyramidal columns 72. The frusto-pyramidal columns 72 are arranged in a regular square array, with each column 72 rotated 45 degrees relative to the array, so that adjacent columns contact one another at one vertex. The frusto-conical columns 72 are hollow, open-ended chimneys, which define passages through which air may flow upwards or downwards through the tray.

(64) Each frusto-pyramidal column 72 comprises four inclined column walls 74, each of which forms a cell wall for a different cell 76, and the wide base of the frusto-pyramids arranged at the bottom end of the cells. Thus, each cell 76 is defined by the sides of four frusto-pyramidal columns, so that the shape of the cell is that of an inverted frusto-pyramid.

(65) As described above in relation to FIG. 4, an arch-shaped contact edge 77 is formed by a change in the angle of the column wall 74. A concave portion 78 is formed in each of the column walls 74, so that the arch-shaped contact edge and the surface of the concave portion 78 lie on a virtual cylindrical surface in the cell. Arch-shaped openings 80 are formed within the concave portions 78 and extend upwards form the cell base to approximately 50% of the column height. At the cell base, the openings 80 have a width approximately equal to one third of the column wall 74.

(66) When a cylindrical stabilised medium of appropriate dimension is inserted into a cell 76, the cylindrical sides of the stabilised media contact the arch-shaped edges 77 and the concave portions 78 of each column wall, and portions of the lower end of the stabilised medium protrude through the openings 80 into the interior of the columns 72.

(67) Similarly to the tray of FIGS. 3a-3e, the columns of the plant tray 70 prevent the free flow of air between cells to improve irrigation and reduce the problem of root bridging between neighbouring cells.

(68) FIG. 6a-6c illustrate a section of a plant-growing tray 82 according to a fourth preferred embodiment of the present invention.

(69) In FIGS. 6a-6c:

(70) PF=Pyramid faces (4 per cell) taper towards base;

(71) SE=Support edges for Ellepot;

(72) VC=Vertical cylindrical cut generates support for Ellepot;

(73) V=Ventilation;

(74) BR=Base rib structure.

(75) Plant-growing tray 82 is similar to plant tray 70 shown in FIGS. 5a-5d. A square array of hollow, open-ended frusto-pyramidal columns, or chimneys, 84 defines a square array of cells 86 therebetween. Compared to the columns 72, however, the frusto-pyramidal columns have a greater draft angle, so that the upper ends of adjacent columns 84 are further apart and are connected by column-connecting walls 88. Inclined walls 90 of the columns 84 and column-connecting walls 88 form cell walls, so that the cells 86 have an upper end with an octagonal shape, tapering to a lower end with a square shape at the cell base.

(76) An arch-shaped opening 92 extends from the lower end of each column wall 90 to an apex approximately 80% of the way up the column wall. The edge of the arch-shaped opening forms an arch-shaped contact edge which follows the intersection of the cell walls with a virtual cylindrical surface. Thus, when a cylindrical stabilised medium is inserted into the cell 86, the stabilised medium contacts the arch-shaped contact edge of the opening 92, and is supported in an upright position.

(77) FIG. 7a-7b illustrate a section of a plant-growing tray 94 according to a fifth preferred embodiment of the present invention.

(78) In FIGS. 7a and 7b:

(79) CF=contact face with Ellepot;

(80) VC=Vertical cylindrical cut to accept Ellepot;

(81) DP=Drafted ‘pyramid’ faces;

(82) V=ventilation;

(83) BR=Base rib structure;

(84) DF=Drafted faces create “pyramid” form toward cell base.

(85) The plant-growing tray 94 of FIGS. 7a and 7b is similar to the plant tray 82 shown in FIG. 6a-6c, with the frusto-pyramidal columns 95 rotated through 45 degrees relative to the array of cells, so that each of the four vertices 96 of each column protrude into a different cell.

(86) In order to accommodate a cylindrical stabilised medium, an arch-shaped opening 97 is formed through each column vertex 96. The edges of the opening 97 thus form contact-edges 98 defining the intersection between two walls and a vertex of the column 95 with a virtual cylindrical surface in the cell. Thus, when a cylindrical stabilised medium is inserted into the cell, the stabilised medium contacts the contact edges 98 of the opening 97, and is supported in an upright position in the centre of the cell.

(87) FIGS. 8 and 9 show an embodiment of a plant tray 400 which is similar to that described above in relation to FIGS. 3a to 3e. In the embodiment of FIG. 8, however, the plant tray 400 additionally comprises four pairs of vertical ribs 410 arranged to project into each cell.

(88) As with the plant tray 40 of FIGS. 3a to 3e, four columns 42 surround each cell 420, and each convex column wall 46 forms a cell wall.

(89) The arch-shaped edges 430 of the openings 54 in the column walls 46 lie on the virtual cylindrical surface in the cell, and thus form contact edges for contacting a cylindrical stabilised medium positioned in the cell.

(90) A pair of vertical ribs 410 projects into the cell 420 from each column wall 46. One rib is positioned on either side of the openings 54, so that the openings 54 and the concave portions 58 are positioned between two ribs. The ribs project from the column walls 46 into the cell, so that the innermost face 440 of each rib is substantially vertical. As the walls of the columns 42 are inclined, this means that in order to provide the vertical face 440 the top end of each rib extends further from the column wall than the bottom end.

(91) The ribs 410 extend from the column base, to the bottom of the upper portion 52 of the columns. The top surface 450 of each rib is level with the lower end of the chamfered upper portion 52, and the top surface of each rib is angled at substantially the same draft angle as the chambered upper portion.

(92) The vertical innermost face 440 of the ribs 410 are angled relative to the column wall, so that the faces 440 follow the virtual cylindrical surface in the cell even though the ribs are not arranged radially around the virtual cylindrical surface. This may advantageously mean that when a cylindrical stabilised medium is inserted into a cell, the outer surface of the stabilised medium contacts both the vertical faces 440 of the ribs 410, and the contact edges 430 formed around the openings 54. By supporting the stabilised medium with both the contact edges 430 and the vertical ribs 410, the likelihood of the stabilised medium tilting out of its intended upright position may be reduced.

(93) FIG. 10 shows an alternative embodiment of a cell 520 for a plant-growing tray. The cell 520 of FIG. 10 is similar to that described above in relation to FIGS. 3a to 3e, 8 and 9. In the embodiment of FIG. 10, however, the cell 520 comprises four vertical ribs 510.

(94) As with the plant tray 400 of FIGS. 8 and 9, the arch-shaped edges 430 of the openings 54 in the column walls 46 lie on the virtual cylindrical surface in the cell, and thus form contact edges for contacting a cylindrical stabilised medium positioned in the cell.

(95) In the cell 520, however, vertical ribs 510 are positioned above each of the openings 54 through the walls of the four columns. The vertical ribs extend upwards from the apex of the openings 54 to the top of the cell. The upper end of the ribs 520 are rounded so that stabilised media may be inserted into and removed from the cell without snagging on the ribs.

(96) By providing ribs 510 above the arch-shaped edges 430 of the openings 54, the innermost faces of the ribs may advantageously lie on the same virtual cylindrical surface as the arch-shaped edges. The ribs 520 may advantageously contact and support a cylindrical stabilised medium at a higher position than the arch-shaped contact edges 430, helping to keep the stabilised medium in its intended upright and central position in the cell.