PLANT GROWTH SYSTEM WITH ROOT BARRIER

Abstract

The invention provides a plant growth system comprising growing substrates (110; 206; 306) as well as plants (P) of which the roots (R) grow in the growing substrate, a number of holding bodies (100; 202; 301) each having a bottom (101; 224; 324) and at least one bottom spacer (104, 105; 9b; 309b), the at least one bottom spacer at the upper side thereof supporting a growing substrate thereon such that a distance is maintained between the bottom and the growing substrate, irrigation means (331) for supplying water to the roots of the plants, drainage means having a drainage opening (241; 341) in the bottom as well as a common drainage which is in communication with each of the drainage openings for allowing water supplied by the irrigation means to the plants to drain via the drainage opening to the common drainage, a water permeable root barrier (123; 205; 305) for each holding body wherein the at least one root barrier is positioned below the upper side of the at least one bottom spacer, upstream of the common drainage for allowing passing of water throught the root barrier to the common drainage but preventing the roots from penetrating throught the root barrier in the common drainage.

Claims

1. A plant growth system comprising: a growing substrate as configured to receive roots of growing plants; a holding body having a bottom surface and at least one bottom spacer having an upper surface supporting the growing substrate thereon such that the bottom surface and the growing substrate are separated by a distance; an irrigation means for supplying water to the growing substrates; a drainage means having a drainage opening defined in the bottom surface and in communication with a common drainage for allowing water supplied by the irrigation means to the growing substrate to drain via the drainage opening to the common drainage; and a water permeable root barrier disposed in the holding body wherein the root barrier is positioned below the upper surface of the at least one bottom spacer and upstream of the common drainage for allowing passing of water through the root barrier to the common drainage while preventing the roots from penetrating through the root barrier into the common drainage.

2. The plant growth system according to claim 1, wherein the root barrier is positioned in or downstream of the drainage opening.

3. The plant system according to claim 2, wherein the bottom surface of the holding body slopes towards one of the root barrier or the drainage opening.

4. The plant growth system according to claim 3, wherein the root barrier has openings with a pore size from about 5 m and to about 100 m.

5. The plant growth system according to claim 1, wherein the root barrier is mounted on a frame which surrounds the root barrier such that the frame with the root barrier is detachably connected to the holding body and wherein the frame includes an additional bottom spacer which is aligned with the at least one bottom spacer.

6. (canceled)

7. (canceled)

8. The plant system according to claim 1, wherein the root barrier has a substantially circular shape.

9. The plant system according to claim 1, wherein the root barrier has a surface area from about 20 cm.sup.2 to about 500 cm.sup.2, the drainage opening has a surface area from about 1 cm.sup.2 to about 100 cm.sup.2, and the root barrier has a surface area from about 15% to about 85% of the surface area of the bottom surface.

10. (canceled)

11. (canceled)

12. The plant growth system according to claim 1, wherein the drainage means further includes a reservoir directly downstream of the root barrier and having an additional bottom surface with an additional drainage opening, the additional bottom surface slopes towards the additional drainage opening.

13. (canceled)

14. The plant growth system according to claim 1, further comprising a circumferential wall extending from the bottom surface, the circumferential wall is integrally formed with the holding body and includes an upper edge that is at a higher level than the upper surface of the at least one bottom spacer the bottom surface, and the circumferential wall define an interior volume configured to accommodate at least a portion of the growing substrate, wherein the holding body further includes at least one wall spacer extending inwards from the circumferential wall configured to maintain a horizontal distance between the circumferential wall and at least the portion of the growing substrate disposed in the interior volume.

15-18. (canceled)

19. The plant growth system according to claim 1, wherein the holding body is made by injection moulding from a polymer material selected from the group consisting of an expanded polystyrene (EPS), a polyethylene (PE), a polypropylene (PP), a polylactic acid (PLA) and combinations thereof.

20. (canceled)

21. The plant growth system according to claim 14, further comprising a cover positioned on the holding body and configured to cover an interior volume defined by the holding body, wherein the cover comprises an opening for receiving a propagation substrate with a plant growing therein.

22. The plant growth system according to claim 21, wherein the cover is made by vacuum moulding, wherein the cover forms at least an upper part of the circumferential wall and includes two cover parts which define the opening in the cover.

23. (canceled)

24. (canceled)

25. The plant growth system according to claim 1, wherein the common drainage includes a closed conduit which is in communication with the drainage opening via a closed sub-conduit.

26. (canceled)

27. The plant growth system according to claim 1, wherein the irrigation means includes irrigation elements configured to provide water to the roots of a single plant through the upper surface of the growing substrate.

28. (canceled)

29. The plant growth system according to claim 27, wherein the irrigation means a water supply; piping for transporting water from the water supply to the irrigation elements; a pump for pumping the water from the water supply through the piping to the irrigation elements; a nutrition reservoir coupled to the water supply; and a mixing unit configured to mix nutrition with the water in the nutrition reservoir provided to irrigation elements.

30. (canceled)

31. (canceled)

32. The plant growth system according to claim 29, wherein each of the irrigation elements includes a dripper.

33. (canceled)

34. The plant growth system according to claim 32, wherein the common drainage and the water supply are in communication with each other via a water recirculation system having a cleaning system for cleaning water from the common drainage.

35. (canceled)

36. The plant growth system according to claim 1, further comprising a propagation substrate positioned on top of the growing substrate.

37. (canceled)

38. Method for growing plants, comprising: positioning a growing substrate on a bottom spacer of a holding body having a root barrier; positioning a propagation substrate each having a plant growing therein on top of the growing substrate allowing growth of roots of the plant into the growing substrate; supplying water through an irrigation element to the propagation substrate and connecting a drainage opening of the holding body with a common drainage to allow water supplied via the irrigation element to the propagation substrate to drain via the drainage opening to the common drainage.

39. The method according to claim 38, wherein the method further comprises: positioning a cover on the holding body to cover an interior volume associated with the holding body, wherein the cover includes an opening for receiving the propagation substrate.

40. (canceled)

41. (canceled)

42. The plant growing system according to claim 1, wherein the growing substrate includes a bag and a substrate material disposed within the bag, the bag having openings with a pore size from about 100 m.sup.2 to about 4000 m.sup.2, allowing plant roots to penetrate the bag while preventing the substrate material to pass through the bag, wherein the substrate material is selected from the group consisting of stonewool, polymeric beads, glasswool, organic fiber, coir, peat, wood fiber, polylactic acid, and combinations thereof.

43-45. (canceled)

Description

FIGURE DESCRIPTION

[0053] The invention will be further elucidated below on the basis of the description of several embodiments of plant growth systems, with reference to the following figures, in which:

[0054] FIG. 1 shows an isometric view of an embodiment of the plant growth system which is not according to the invention as claimed in the present application;

[0055] FIG. 2 shows an isometric view of an embodiment of the holding body for use in the plant growth system according to the invention;

[0056] FIGS. 3a and 3b show two vertical cross sections of the embodiment according to FIG. 2 which cross sections are perpendicular to each other;

[0057] FIGS. 4a, 4b and 4c respectively show an perspective exploded view, a top view and a side view of the drainage means for use in the holding body of the plant growth system according to FIG. 2;

[0058] FIG. 5 shows a schematic cross section of an embodiment of a holding body according to the present invention;

[0059] FIG. 6 shows a perspective view of an embodiment of a holding body according to the invention.

[0060] FIG. 7 shows the holding body according to FIG. 6 in combination with a growing substrate;

[0061] FIG. 8 shows the holding body of FIG. 6 in combination with a growing substrate and a cover;

[0062] FIG. 9 shows a side view of the embodiment of the holding body shown in FIG. 8;

[0063] FIG. 10 shows a vertical cross sectional view of the holding body shown in FIG. 8 or 9;

[0064] FIG. 11 shows a cross sectional view of a couple of holding bodies which are stacked;

[0065] FIG. 12 shows in isometric view a root barrier to be used in combination with the holding body as shown in FIG. 6.

[0066] FIG. 1 depicts an embodiment of a plant growth system 1 which is not according to the invention. Its present description is however considered usefull to properly understand and appreciate the invention to which FIGS. 3 to 12 relate.

[0067] The plant growth system 1 comprises a box 2. The box includes a lower part having a circumferential wall 22 and a bottom 24. Together with the bottom 24, the circumferential wall 22 defines a lower part of an interior volume 21 of the box 2. The box 2 further comprises a cover 23 with a cover plate 28 and a circumferential wall 29 which extends downwardly from the circumference of the cover plate 28. This circumferential wall 29 is aligned with the circumferential wall 22. In the centre of the cover plate a square opening 20 is provided. The holding body 2 is made from a plastic material, such as expanded polystyrene (EPS), polyethylene (PE), polypropylene (PP), or polylactic acid (PLA).

[0068] Near the bottom 24 of the box 2 a drainage opening 41 is provided in the circumferential wall 22. The drainage opening 41 connects to a common drainage embodied as a pipe 35 via a tube 34.

[0069] The box 2 is further provided with a cloth-like root barrier 5 which is clamped between the circumferential wall 22 and the circumferential wall 29. The root barrier 5 has mesh openings with a pore size of for instance 50 m or 70 m. Such pore size allows the passage of water through the root barrier 5 but prevents the passage of roots. The root barrier 5 divides the interior volume 21 of the box 2 in an upper part and a lower part. In the upper part substrate material 6 is provided whereas in the lower part a further substrate material 8 is provided. The further substrate material 8 supports the growing substrate and prevents the root barrier 5 to sag under the influence of the weight of the substrate material 6. Substrate material 6 can comprise mineral or glass wool, but can also comprise plastic beads such as made from expanded polystyrene (EPS).

[0070] A propagation substrate 7, shaped as a stable block, is positioned on top of the growing substrate 6, more in particular at the location of opening 20 of cover plate 28. A plant P is growing in the propagation substrate 7. The positioning of the propagation substrate 7 on top of the growing substrate 6 allows the roots of the plant P to grow into the substrate material 6.

[0071] The system 1 comprises irrigation means 3 comprising irrigation elements embodied as dripper 31 for supplying water, possibly containing nutrition, to the roots of the plant P in the substrate material 6 in the interior volume 21 via the upper side of the propagation substrate 7 and via the upper side of the substrate material 6. The dripper 31 is positioned in the propagation substrate 7 and configured to release drops of water in the propagation substrate 7. At the upper end the dripper 31 is connected via a tube 33 to a common water supply embodied as a pipe 32.

[0072] In use boxes 2 will typically rest on the elevated, flat, middle part of a gutter having an -shaped vertical cross section. The pipes 32 and 35 will rest on the lowered opposite parts of the -shape and are part of a closed circuit which prevents light and dust being able to reach the water within the circuit.

[0073] In practise, water from the dripper 31 will travel downwards through the propagation substrate 7 and the substrate material 6 in the interior volume 21. The roots of plant P can absorb this water. Also, when nutrition is provided by the dripper 31, the roots can absorb this nutrition. It is also possible that the propagation substrate 7 and/or the substrate material 6 comprises nutrition which is added to the water as supplied via the dripper 31.

[0074] The water provided by the dripper 31 will pass the root barrier 5 as it travels through the substrate material 6 and the further substrate material 8. When water reaches the drainage opening 41, it is guided out of the holding body 2 via tube 34. The root barrier is water permeable, which means that the root barrier is suitable for allowing water to pass the barrier 5. However, the roots of plant P cannot pass the root barrier 5. The root barrier 5 is positioned upstream of the drainage opening 41. This way it is prevented that roots grow into the drainage opening 41, or into the tube 34 or the common drainage pipe 35. This could lead to an obstruction for the water flow and would likely disturb the growing process of plant P.

[0075] Although FIG. 1 only shows one box 2, in practice the system will comprise a number of similar boxes 2 which each are in communication with the common drainage pipe 35 and the common water supply pipe 32.

[0076] The system 1 as shown in FIG. 1 and as described above is not according to the invention since it does not comprise holding bodies each with at least one bottom spacer extending upwards from the bottom of the holding body and since it does not comprise a root barrier which is positioned in or downstream of the drainage opening. Other aspects of the present invention however are embodied in the system 1.

[0077] FIGS. 2 to 4c relate to a holding body 202. The holding body 202 can be used in a plant growth system according to the current invention. Holding body 202 is made from different components. The bottom 224 is connected with the circumferential wall 222. Bottom 224 and wall 222 could however also be one integral part. The bottom 224 and the wall 222 define a interior volume 221 having an open upper side 223 on which a cover may in use be placed. In use the interior volume 221 accommodates a growing substrate 206.

[0078] A root barrier unit 204 which has a square circumference in top view, is provided in a drainage opening 241 in the bottom 224 of the holding body 202. To this end, a square recess is provided in the bottom 224 the upper side of which constitutes the drainage opening 241. The root barrier unit 204 is provided with a reservoir 44 (FIGS. 3a and 3b). A circular frame 210 is shape fitted received in a further circular recess in the basically rectangular frame of the root barrier unit 203. The root barrier unit 204 further comprises a further drainage opening 49 in the further bottom 245 of the reservoir 44 via which an elbow pipe 43 is communicatively connected to reservoir 44. In use the elbow pipe 43, like elbow pipes 43 associated with other holding bodies 202, will be communicatively connected with its downstream end to a common drainage pipe like drainage pipe 35 forming part of a closed recirculation circuit. A root barrier 205 is mounted to the frame 210. The frame 210 is connected to the rectangular frame of the root barrier unit 204 in such a way that the drainage opening 241 is closed off for the roots of a plant.

[0079] The holding body 202 further comprises a base frame 225. The base frame 225 is provided underneath the bottom 224 and serves as a support. The base frame 225 is suitable for keeping the holding body 202 stably in place. FIG. 3a shows that the bottom 224 slopes towards the drainage opening 241 and bottom spacers 9b which extend upwards from the bottom 224. In use, the spacers 9b provide a space between a growing substrate 206 and the bottom 224. The upper surfaces of the spacers 9b are substantially flat and aligned with, or in other words flush to, each other such that a growing substrate 206 can rest on the spacers 9b.

[0080] The base frame 225 comprises an arc-shaped recess at its lower side as shown in FIG. 3b. The arc-shaped recess 231 is suitable to engage with a flat support, such as the elevated middle part of a gutter having an -shaped vertical cross section, having a width which is smaller than the arc-shaped recess. In case the support would not be perfectly horizontal the arc-shaped recess 231 provides a means for compensating this such that the holding body 202 is oriented as desired.

[0081] The frame 210 is provided with a root barrier 205. The reservoir 44 has a rectangular cross section. However, it is also possible that the reservoir 44 is funnel shaped, wherein the further bottom 245 of the reservoir 44 is sloping towards the elbow pipe 43.

[0082] FIGS. 4a to 4c show different views of the root barrier unit 204 including in FIG. 4a with frame 210. The root barrier unit 204 is provided in a recess in the bottom 224 of the holding body 202.

[0083] In use, water which is being irrigated by drippers via the upper side 209 of the growing substrate 206, flows downwards through the root barrier 205, into the reservoir 44. Water is, temporarily, collected in the reservoir 44, after which the water continues through the opening 49 in the bottom 245 of the reservoir 44 and into the elbow pipe 43 and further to a common drainage pipe. The root barrier 205 is flat and is circle-shaped. Also, frame 210 comprises a circle shaped cross section. In this embodiment, the frame 210 with the root barrier 205 mounted thereon is detachably connected to the holding body 202. Although not shown in the figure, the reservoir may be funnel-shaped, the further bottom 245 sloping towards the further drainage opening 49 such that water is easily guided to the elbow pipe 43.

[0084] FIG. 5 shows a cross sectional view of a plant growth system 301. A first multitude of side spacers 309a is adjacent to the circumferential wall 322 of the holding body 301. The side spacers 309a extend between the plant growing substrate 306 and the circumferential wall 322. The holding body 301 also comprises bottom spacers 309b which extend upwards from the bottom 324 of the holding body 302. The spacers 309b extend in the interior volume 321 of the holding body 302 which interior volume 321 is defined by the bottom 324 and the wall 322. Within the interior volume 321 a growing substrate 306 is accommodated while being supported on the bottom spacers 309b. The side spacers 309a ascertain a distance between the circumferential wall 322 and the plant growing substrate 306 and are configured such that air can flow in a vertical direction along the side spacers 309a to the space 308 below the lower side of the growing substrate 306 and the bottom 324. This space 308 is present because of bottom spacers 9b which support the growing substrate 306 and create a distance and space between the bottom 324 and the plant growing substrate 306. The growing substrate 306 support a propagation substrate 307 with a plant P. A dripper 331 is stuck in the propagation substrate 307. The roots R of the plant P grow both in the propagation substrate 307 as well as in the growing substrate 306.

[0085] The holding body 302 comprises a cover 223. The cover 323 may be connectable to the circumferential wall 322, for instance using a snap connection. The cover 323 covers the open upper side of the holding body 302. The cover 323 comprises an opening for receiving the substrate block 307 with the plant P growing therein onto the plant growing substrate 306.

[0086] In the bottom 324 a drainage opening 341 is provided which connects to a drainage pipe 342. Within the pipe 342 below the drainage opening 341 a root barrier 305 is provided. Downstream of the root barrier 305 the pipe 342 connects to a common drainage pipe just like other pipes 342 of other holding bodies 302.

[0087] FIGS. 6 to 12 relate to a system with another holding body 100. The holding body 100 is tray-like. The holding body 100 comprises a bottom 101 and a circumferential wall 102 that together define a part of an interior volume. The bottom 101 is provided with an opening 131 for receiving a root barrier frame 120 (FIG. 12) with a root barrier 123 mounted thereon. The tray-like holding body 100 further comprises a base frame 103 at its lower side.

[0088] The holding body 100 is provided with bottom spacers 104, 105 above bottom 101 and side spacers 106. Bottom spacers 104 are substantially free from the circumferential wall 102.The bottom spacers 105 extend substantially adjacent the circumferential wall 102. In use the respective upper sides of the spacers 104, 105, which are aligned with each other, support a growing substrate. The side spacers 106 are connected to the bottom spacers 105, and have a vertical positioning surface at a short distance from the circumferential wall 102. When a growing substrate 110 is positioned on the holding body 100, the bottom spacers 104, 105 support the growing substrate 110 such that a vertical distance is maintained between the lower side of the growing substrate 110 and the bottom 101. The side spacers 106 ensure that a horizontal distance is maintained between the vertical sides of the growing substrate 110 and the circumferential wall 102. The upper edge 109 of the circumferential wall 102 is located for instance 20 mm above the upper sides of the bottom spacers 104, 105 reducing the amount of light and dust which in use enters the space 108 between the bottom 101 and the lower side of the growing substrate 110.

[0089] A cover 115 can be positioned onto the holding body 100, more in particular on the circumferential wall 102 thereof. The cover 115 comprises a base plate 117 and a circumferential wall 116 extending downwards from said base plate 117. A shape fitting connection may be used between the holding body 100 and the cover 115. The circumferential wall 116 of the cover 115 defines the interior volume of the holding body 100 together with the circumferential wall 102 of the holding body 100.

[0090] The cover 115 comprises two openings 118 in the base plate 117. In these openings 118 a propagation substrate (not visible) can be positioned on top of the growing substrate 110.

[0091] A root barrier frame or unit 120 is positioned in a circular drainage 111 opening in the bottom 101 of the holding body 100. The root barrier frame 120 comprises a circular outside wall 121 which is connected via ribs 124 to a root barrier bottom spacer 122 within the circumference of the circular outside wall 121. A root barrier 123 is mounted on the root barrier frame 120, between the root barrier bottom spacer 122 and the outside wall 121. The upper side of the root barrier bottom spacer 122 is aligned with the upper sides of the bottom spacers 104. In use, the substrate 110 tends to loose some stiffness due to the usage of the substrate 110. The root barrier spacer 122 supports the substrate 110 above the root barrier 123 in order to prevent the substrate 110 from sinking towards the root barrier 123.

[0092] The outside wall 121 is designed such to provide a shape fitted watertight connection with the drainage opening in the bottom 101. At the outside wall 121 an engagement portion 125 is provided. When the root barrier frame 120 is assembled with the holding body 100, the engagement portion 125 extends upwards from the bottom 101 wherein the engagement portion 125 is free from the bottom 101 such that the engagement portion 125 can be grabbed by a person to remove the root barrier frame 120 from the bottom 101 of the holding body 100.

[0093] The tray-like holding bodies 100 are stackable. This is shown with more detail in FIG. 11. Each holding body 100 comprises a hollowed bottom structure 130 at an underside of the holding body 100. Because each of the tray-like holding bodies 100 has a similar hollowed bottom structure, the trays can be stacked on top of each other.

[0094] The following clauses define several aspects and embodiments of the invention: [0095] 1. Plant growth system comprising [0096] a number of holding bodies each having a bottom and a circumferential wall extending from the bottom, as well as an interior volume for accommodating at least the roots of at least one plant, the interior volume at least party being defined by the bottom and the circumferential wall, [0097] irrigation means for supplying water to plants of which at least the roots are accommodated in the interior volumes of the respective holding bodies, [0098] drainage means having a drainage opening in the bottom or circumferential wall of each holding body as well as a common drainage which is in communication with each of the drainage openings for allowing water supplied by the irrigation means to the plants to drain via the drainage opening from the interior volume of the holding body to the common drainage, [0099] characterized in that [0100] the system further comprises a water permeable root barrier for each holding body wherein each root barrier is positioned upstream of the common drainage for allowing passing of water through the root barrier and through the drainage opening but preventing roots in the interior volume of an associated holding body from penetrating through the root barrier in the common drainage. [0101] 2. Plant growth system according to clause 1, wherein the root barriers are positioned in the interior volume of the respective associated holding bodies. [0102] 3. Plant growth system according to clause 1, wherein the root barriers are positioned in the drainage opening of the respective associated holding bodies. [0103] 4. Plant growth system according to clause 1, wherein the root barriers are positioned downstream of the drainage opening of the respective associated holding bodies. [0104] 5. Plant growth system according to any of the preceding clauses, wherein the root barriers have openings with a pore size ranging between 5 m and 100 m, preferably ranging between 10 m and 75 m. [0105] 6. Plant growth system according to any of the preceding clauses, wherein the root barrier is mounted on a frame which surrounds the root barrier. [0106] 7. Plant growth system according to clause 6, wherein the frame with the mounted root barrier is detachably connected with or integrated to the holding body, preferably with or to the bottom of the holding body. [0107] 8. Plant growth system according to any of the preceding clauses, wherein the root barrier has at least substantially the shape of a circle. [0108] 9. Plant growth system according to any of the preceding clauses, wherein the root barrier has a surface ranging between 20 cm2 and 500 cm2, preferably ranging between 25 cm2 and 100 cm2 or ranging between 200 cm2 and 450 cm2. [0109] 10. Plant growth system according any of the previous clauses, wherein the drainage opening has a surface ranging between 1 cm2 and 100 cm2, preferably ranging between 5 cm2 and 50 cm2. [0110] 11. Plant growth system according to any of the previous clauses, wherein the root barrier is provided in the bottom of the holding body [0111] 12. Plant growth system according to clause 11, wherein the surface of the root barrier ranges between 25% and 75% of the surface of the bottom. [0112] 13. Plant growth system according to clause 11 or 12, wherein the bottom of the holding body slopes towards the root barrier and/or towards the drainage opening. [0113] 14. Plant growth system according to any of the previous clauses, wherein the drainage means comprise a reservoir directly downstream of the root barrier and having a bottom in which the drainage opening is provided, the bottom of the reservoir preferably sloping towards the drainage opening. [0114] 15. Plant growth system according to any of the previous clauses, wherein the holding body comprises at least one wall spacer extending inwards from the circumferential wall for maintaining a distance between the circumferential wall and a growing substrate in the interior volume. [0115] 16. Plant growth system according to any of the previous clauses, wherein the holding body comprises at least one bottom spacer extending upwards from the bottom for maintaining a distance between the bottom and a growing substrate in the interior volume. [0116] 17. Plant growth system according to any of the previous clauses, wherein the circumferential wall of the holding body is formed out of a rigid material. [0117] 18. Plant growth system according to any of the previous clauses, wherein the holding body is made from a plastic material, preferably chosen from the group consisting of expanded polystyrene (EPS), polyethylene (PE), polypropylene (PP) or polylactic acid (PLA). [0118] 19. Plant growth system according to any of the previous clauses, wherein the holding body comprises a cover which is to be positioned on the circumferential wall for covering the interior volume of the holding body, wherein the cover comprises an opening for receiving a propagation substrate with a plant growing therein. [0119] 20. Plant growth system according to clause 19, wherein the cover comprises two cover parts which together from the opening in the cover. [0120] 21. Plant growth system according to any of the previous clauses, wherein the common drainage comprises a closed conduit. [0121] 22. Plant growth system according to clause 21, wherein the closed conduit is in communication with each of the drainage openings via closed sub-conduits. [0122] 23. Plant growth system according to any of the previous clauses, wherein the irrigation means comprise a common water supply for supplying water to a plurality of irrigation elements, wherein each irrigation element is suitable for providing water to a plant of which at least the roots are accommodated in the interior volumes of the respective holding bodies. [0123] 24. Plant growth system according to clause 23, wherein the common drainage and the common water supply are in communication with each other via a water recirculation system. [0124] 25. Plant growth system according to any of the preceding clauses, wherein the system comprises plant growing substrates which are accommodated in the interior volumes of the respective holding bodies. [0125] 26. Plant growth system according to any of the preceding clauses, wherein the system comprises propagation substrates each with a plant growing therein which propagation substrates are positioned at the upper side of the interior volumes of the respective holding bodies. [0126] 27. Method for growing plants, in particular but not exclusively performed in a greenhouse, using the plant growth system according to any of the previous clauses, comprising the steps of: [0127] a. providing a number of holding bodies each with an associated root barrier, [0128] b. positioning propagation substrates each having a plant growing therein at the upper side of the interior volumes of the respective holding bodies allowing the growth of the roots of the plants into the associated respective interior volumes, [0129] c. providing an irrigation element for each propagation substrate for allowing the supply of water to the propagation substrate via the associated irrigation element, [0130] d. bringing the drainage openings on the one hand and the common drainage on the other hand in communication with each other for allowing water supplied via the irrigation elements to the propagation substrate to drain via the drainage opening from the interior volume of the associated holding body to the common drainage, [0131] 28. Plant growing method according to clause 27, wherein the method further comprises the step of: [0132] e. before step b. placing a growing substrate in the interior volume of the holding body, and [0133] f during step b. placing the propagation substrate on top of the growing substrate. [0134] 29. Plant growing method according to clause 27 or 28 wherein the method further comprises the step of: [0135] g. providing a cover for covering the interior volume of the holding body. [0136] 30. Greenhouse provided with the system according to any of the clauses 1 to 26. [0137] 31. Holding body for use in the system according to any of the clauses 1 to 26, having a bottom and a circumferential wall extending from the bottom, as well as an interior volume for accommodating at least the roots of at least one plant, the interior volume at least party being defined by the bottom and the circumferential wall, a drainage opening being provided in the bottom or circumferential wall which drainage opening is to be brought into communication with a common drainage downstream of the drainage opening, the holding body further having a water permeable root barrier for allowing passing of water through the root barrier and through the drainage opening but preventing roots in the interior volume of an associated holding body from penetrating through the root barrier in the common drainage, the root barrier being positioned in the interior volume or in the drainage opening of the holding body. [0138] 32. Plant growing substrate for use in a system according to any of the clauses 1 to 26, comprising a bag and substrate material within the bag, the material of the bag having openings with a pore size having a surface ranging from 100 m.sup.2 to 4000 m.sup.2, allowing plant roots to penetrate the material of the bag but preventing substrate material to pass through the material of the bag. [0139] 33. Plant growing substrate according to clause 32, wherein the substrate material is one or a combination of stonewool, glasswool, wood fiber and/or polylactic acid. [0140] 34. Plant growing substrate according to clause 32 or 33, wherein the substrate material are beads of plastic material, preferably of polylactic acid. [0141] 35. Use of a plant growth system according to any of the clauses 1 to 26 for growing plants.