Abstract:
The present invention relates to the field of plant growth units, and more particularly pertains to an apparatus for plant cultivation which conserves horizontal space and utilizes vertical space, while providing for the growth of plants which are cultivated in an indoor environment. The plant growth unit comprises a nutrient supply module and one or more columns radially disposed about a central vertical longitudinal axis thereby defining an internal space between the one or more columns designed to accommodate a light source. Each column is in fluid communication with the nutrient supply module for circulation of a liquid nutrient flow. The one or more columns support a plurality of growth sites, which are radially disposed about the longitudinal axis and generally face the internal space. Each growth site is positioned to contact the liquid nutrient flow.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of plant growth units. 
     BACKGROUND OF THE INVENTION 
     Plant growth units which attempt to conserve horizontal space and utilize vertical space, are known. A typical hydroponic plant growth system comprises a nutrient base and circulates a liquid nutrient through a cultivation portion wherein the plant seeds or young plants are anchored. For example, U.S. Pat. No. 5,502,923 discloses a hydroponic plant growth system which consists of a nutrient supply module base which supplies liquid nutrient to a series of vertically stacked prop modules, each prop module containing a number of plant growth sites. As liquid nutrient is pumped to each prop module, water is distributed to the plants grown therein. 
     U.S. Pat. No. 4,986,027 discloses a plant growth apparatus comprising a flexible tubular element wherein slits are provided for the growth of plants. A fluid nutrient is supplied to the root permeable material via a pump system, the fluid nutrient thereby being supplied to the plants. 
     Similarly, U.S. Pat. Nos. 5,440,836, 5,555,676, 5,918,416 and 4,033,072 all disclose vertical growing columns for growing a number of plants which are supplied water and nutrients through the use of nutrient solution pumps in the base of the respective apparatuses, which supply liquid nutrient to the top of the apparatuses. The liquid nutrient is supplied to the plants as the liquid travels from the top of the apparatuses to the bases. 
     Further, the prior art indicates that multiple vertical plant grow columns may utilize a single nutrient base. For example, U.S. Pat. No. 5,363,594 discloses a structure for a vertically oriented plant growth unit having a plurality of vertical columns arranged to conserve horizontal floor space and utilize a common base for the supply of liquid nutrient. 
     One of the potential limitations of the growth units described above is that the various plants of the growth units may receive different types and amounts of light from whatever light source is utilized. The differences in light quality and quantity may result in a divergence in growth and quality between plants grown at various levels and on various sides of the vertical columns. 
     U.S. Pat. No. 6,178,692 discloses a lighting system for use with one or more vertical growing columns. The lighting system is mobile and can apparently be angled to provide for equidistant lighting to the plants at both the top and the bottom of the vertical growth column. However, it would appear that equidistant lighting is to be provided by the lighting apparatus to a single side of each growth column. Each vertical column apparently has plants growing on all sides of the vertical unit and therefore a single lighting unit would appear only to provide equidistant lighting to those plants which are somewhat facing the lighting unit. To provide equidistant lighting to all plants on the growing columns, it would appear that two lighting units are set up on either side of one or more growing columns and angled to provide top to bottom equidistant lighting on each side of the vertical grow columns, thereby providing equidistant lighting to all plants. In at least some embodiments, this system therefore appears to be limited by the requirement for multiple lighting units to create equidistant lighting to all plants. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a plant growth unit including a nutrient supply module, one or more columns and a plurality of growth sites supported by the one or more columns. The nutrient supply module may be designed to contain a liquid nutrient. The one or more columns may be radially disposed about a central vertical longitudinal axis to define an internal space between the one or more columns. The internal space may be adapted to acconmmodate a light source. Each column may have an upper portion, a lower portion and a longitudinal passage through which the liquid nutrient may pass. Further, each column may be in fluid communication with the nutrient supply module for circulation of a liquid nutrient flow from the nutrient supply module to the upper portion of each of the one or more the columns and through the longitudinal passage to the respective lower portion of each of the one or more columns. The plurality of growth sites may be radially disposed about the longitudinal axis of the growth unit, generally facing the internal space, and each growth site may be positioned to contact the liquid nutrient flow. 
     In some embodiments, there are at least two columns and at least one growth site on each column. Such columns may be vertically oriented. In yet other embodiments, the growth unit has at least three columns, which may be circumferentially disposed in a generally circular pattern. In other embodiments, there is only one column which contains a plurality of growth sites. In such an embodiment, the single column defines its internal space by, for example, coiling around the longitudinal axis. 
     In accordance with some embodiments, two or more of the growth sites are approximately equidistant from the longitudinal axis. In other embodiments, at least two growth sites are located on each of the one or more columns and at least some of the growth sites on each column are vertically spaced apart. In such an embodiment, the growth sites at generally the same vertical level may be approximately equidistant from the longitudinal axis. In still other embodiments, the growth unit comprises at least two columns and at least two growth sites are located on each column. In such an embodiment, the growth sites on each column may be vertically spaced apart, and growth sites at generally the same vertical level may be approximately equidistant from the longitudinal axis. 
     The nutrient supply module may act as a base into which the columns are located, and may be shaped to facilitate balance of the system, such as disc shaped. The columns may be shaped to facilitate the nutrient flow from the upper portion of each of the columns to the lower portion of each of the columns, such as tubular columns. 
     The plant growth unit may further include one or more fluid connectors, such as tubes, which connect the nutrient supply module with the upper portion of each of the one or more columns. The fluid connectors may be designed to facilitate the liquid nutrient flow from the nutrient supply module to the tops of each of the one or more columns. The plant growth unit may also include a pump, or pumps, facilitating the liquid nutrient flow. 
     Where each column supports a plurality of growth sites, the growth sites may be longitudinally aligned. In some embodiments, the growth sites may protrude upwardly from the columns. The plant growth unit may also include a plurality of baskets which are designed to hold plants and designed to attach to the growth sites. The plants may be anchored to the growth unit by being placed inside the baskets, which are then attached to the growth sites. 
     Other embodiments of the present invention provide methods for growing plants in a growth unit. A nutrient supply module may be adapted for holding a liquid nutrient. One or more columns may be radially disposed about a central vertical longitudinal axis of the growth unit, thereby defining an internal space between the one or more columns. The columns may be disposed in fluid communication with the nutrient supply module and the internal space may be adapted to accommodate a light source. Each column may be designed with an upper portion, a lower portion and a longitudinal passage through which the liquid nutrient may pass. The nutrient supply module may be connected to the upper portion of the columns. A plurality of growth sites may be provided supported by the columns. The growth sites may be disposed radially about the longitudinal axis and generally facing the internal space. A plurality of plants may be then be located in the growth sites and the liquid nutrient may be added to the supply module. The liquid nutrient may then be circulated from the nutrient supply module to the upper portion of each of the one or more columns, through the longitudinal passage to the respective lower portion of each of the one or more columns. During its circulation, the liquid nutrient may be brought into contact with the plants. 
     In such a method, the introduction of a plurality of growth sites may further include locating at least two of growth sites equidistant from the longitudinal axis. During the introduction of a plurality of growth sites, at least two growth sites may be introduced on each of the one or more columns, at least some of such growth sites being vertically spaced apart on the columns. In such a method, the growth sites being at generally the same vertical level may be located approximately equidistant from the longitudinal axis. In another such method, at least two columns may be disposed and at least two growth sites may be introduced on each of the columns, such growth sites being vertically spaced apart on each column. In such a method, the growth sites which are at generally the same vertical level may be located approximately equidistant from the longitudinal axis. 
     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only, and not as limiting the invention to particular embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In drawings which illustrate the embodiments of the invention, 
     FIG. 1 is an isometric view of a plant growth unit according to an embodiment of the invention 
     FIG. 2 is a longitudinal cross-sectional view of the plant growth unit of FIG. 1 
     FIG. 3 is an elevational side view of a plant growth unit, in an embodiment including two columns 
     FIG. 4 is a top view of the plant growth unit of FIG. 1 
     FIG. 5 is a bottom view of the plant growth unit of FIG. 1 
     FIG. 6 is a longitudinal broken away cross-sectional of a portion of the of the plant growth unit of FIG. 1 
     FIG. 7 is an elevational view of a plant growth unit, in an embodiment which includes a single column 
    
    
     DETAILED DESCRIPTION 
     Referring collectively to FIGS. 1,  2  and  4  through  6 , a plant growth unit according to one embodiment is shown. The plant growth unit includes a nutrient supply module  10 , a plurality of columns  20 , and a plurality of growth sites  30  supported by the columns  20 . 
     The nutrient supply module  10  is designed to contain a liquid nutrient  12 . In the embodiment shown, the nutrient supply module  10  acts as a base for the plant growth unit. The nutrient supply module  10  thereby stabilizes the plant growth unit and the columns  20  contained therein. However, the nutrient supply module need not act as a base for the growth unit which may be anchored or stabilized by alternative structures or supports. 
     The nutrient supply module  10  as shown in FIGS. 1 through 5 is disc shaped. However the nutrient supply module may take on various shapes adapted to enable it to act as a nutrient supply module in fluid communication with the columns  20 . Where the nutrient supply module  10  is intended to act as a base for the growth unit, it may be designed to maintain balance and support of the growth unit when placed on its intended surface. 
     The nutrient supply module  10  may have a hole in the upper portion of the nutrient supply module  10  located approximately at the longitudinal axis  40 , such a hole being adapted to hold a mesh basket for collecting medium and dead foliage to later be discarded, a allowing excess liquid nutrient  12  to pass into the nutrient supply module  10 . It is not necessary that the nutrient supply module  10  have such a hole. The outer portion of the upper surface of the nutrient supply module  10  may also slope downwardly towards the longitudinal axis  40 , allowing excess liquid nutrient  12  dripping from the columns  20  to drain towards the longitudinal axis  40  and the hole which may be present in the nutrient supply module  10 . The upper surface of the nutrient supply module  10  may also be level, or may slope in other directions. 
     The nutrient supply module  10  may be made of plastic, such as food grade polyethylene or food grade polycarbonate. The nutrient supply module  10  may be manufactured by, for example, placing food grade polyethylene powder in an aluminum mold, which is then heated and rotated on two separate axes. The food grade polyethylene in the mold melts as the mold is heated and the centripetal force of the rotation forces the melted plastic to the walls of the aluminum mold where it cools as the mold is removed from the heat. The nutrient supply module  10  is then removed from the mold. In alternative embodiments, the nutrient supply module  10  may be manufactured from a variety of other materials capable of containing the liquid nutrient  12  and allowing for fluid communication with the columns  20 . 
     In the illustrated embodiment of FIGS. 1,  2 , and  4  through  6 , the columns  20  are radially disposed about a central vertical longitudinal axis  40  and define an internal space  42  between the columns  20 . In the embodiments illustrated in FIGS. 1,  2  and  4  through  6 , four columns  20  are disposed approximately equidistant from the longitudinal axis  40  and approximately equidistant from each other, as shown in FIG.  4 . Any number of columns  20  may be arranged about the longitudinal axis  40 . For example, as shown in FIG. 3, two columns  20  may be radially disposed about the longitudinal axis opposite each other. The columns  20  may be equidistant from the longitudinal axis  40  and equidistant from each other. Where there are at least three columns, the columns may be circumferentially disposed in a generally circular pattern. In alternative embodiments, the columns  20  need not be equidistant from the longitudinal axis  40  or each other, while the columns  20  remain radially disposed about the longitudinal axis  40  and define an internal space  42 . 
     The columns  20  are generally vertically oriented and generally straight in the embodiments shown in FIGS. 1 through 6. In alternative embodiments, it is not necessary that the columns be vertically oriented and/or straight. The columns may be angled in any direction, and at any degree. For example, the columns may be tilted towards or away from the longitudinal axis  40 . The columns may also be of various appropriate curvatures or shapes. Appropriate curvatures and shapes of the columns may be selected so as to maintain the other functional objectives of the various embodiments of the invention. 
     The internal space  42  may be adapted to accommodate a light source. The light source may be, for example, a tubular light source which can be supported, for example by hanging, vertically between the columns  20  in the internal space  42 . In some embodiments, for generally equidistant lighting and advantageous conditions for all plants growing in the growth unit, the tubular light source may be supported approximately along the longitudinal axis. Alternatively, as shown in the alternative embodiment of FIG. 3, the light source could be a series of bulbs  44  supported vertically between the columns  20  in the internal space  42 , in some embodiments the series of bulbs  44  being aligned approximately along the longitudinal axis for generally equidistant lighting. A series of bulbs  44  may, for example, be vertically supported hung by a chain  46 , or other support, from, for example, a support beam  48 . The light source could also, for example, be a bulb hung in the internal space, or supported in the internal space by the base along the longitudinal axis. Appropriate bulbs for use as a light source include 400 watt Metal Halide, 400 watt High Pressure Sodium, 250 watt Metal Halide, 250 watt High Pressure Sodium and 430 watt Son Agro. Larger bulbs, such as 600 watt High Pressure Sodium, 1000 watt High Pressure Sodium or 1000 watt Metal Halide, may also be used; however, when larger bulbs such as these are used as a light source for the plant growth unit, they may have to be continuously moved up and down the longitudinal axis when lit. 
     Each column  20  may have an upper portion  22 , a lower portion  24  and a longitudinal passage  26  through which the liquid nutrient  12  may pass. The columns  20  may be tubular, thereby defining the longitudinal passage  26 . The columns  20  may be made of plastic or another suitable material, such as clay, metal or wood. The columns  20  may, for example, be manufactured by way of known injection mold techniques, or extruding plastic techniques. Alternatively, the columns  20  could be manufactured from pre-existing ABS or PVC elbows, Tee&#39;s and straight lengths, which can be glued together. Metal elbows, Tee&#39;s and straight pipes could be welded together to form the columns  20 . The columns  20  could alternatively be carved from wood, or other carvable material, or could be formed by gluing or nailing wooden planks together to form square columns. A column may also be formed from clay by shaping clay pieces and then mounting the clay pieces into a column. 
     The columns  20 , in the embodiments shown, rest on the bottom of the nutrient supply module  10  and have a hole in the column such that the liquid nutrient flow  14  may pass out of the lower potion  24  of the columns  20 . In alternative embodiments, the columns  20  may be supported above the bottom of the nutrient supply module and the liquid nutrient flow  14  may pass out of the bottom of the columns  20 . 
     In some embodiments, the longitudinal passage  26  may be hollow or may contain a permeable material, such as a planting medium, through which the liquid nutrient  12  is able to pass. Suitable planting medium includes, but is not limited to, Hydroton™ (or other small round, kiln heated clay types), Sunshine Mix™ (or other peat perlite soil like mixes), perlite, vermiculite, rockwool, washed rock, sand, foam or animal castings. The permeable material is also not limited to planting medium. It may be possible to use a wide range of material which allows for the passage of the liquid nutrient  12  through the longitudinal passage  26 , while still allowing the growth unit to meet the other finctional objectives of various embodiments of the invention. 
     Each column  20  may be in fluid communication with the nutrient supply module  12  for circulation of a liquid nutrient flow  14 . In the embodiments shown in FIGS. 1 through 6, a plurality of pumps  16  circulate the liquid nutrient  12  from the nutrient supply module  10  through a plurality of tubes  18  to the upper portion  22  of each of the columns  20  and through the longitudinal passage  26  to the respective lower portion  24  of each of the columns  20 . In alternative embodiments, a single pump may facilitate the liquid nutrient flow  14 . In some embodiments, once the liquid nutrient is pumped to the end of the tubes  18  at the upper portion  22  of each of the columns  20 , the liquid nutrient is allowed to cascade down the longitudinal passage and back into the nutrient supply module  10  via gravitational pull. The pumps  16  may be, for example, Little Giant™ sump pump 1200 gph, or other such pumps manufactured by Magdrive™ and Rio™. The tubes  18  may be, for example, ½ inch commercial garden hose, ½ inch rubber garden hose, ½ inch ABS hose or other size hoses of the same type. The system connecting the tubes  18  to the columns  20  and the pump(s)  16  may incorporate ABS elbows, ABS stop plugs, hose clamps, rubber washers, ½ inch ABS tees, ½ inch shut off values and female to male hose adaptors, arranged to facilitate the liquid nutrient flow  14 . Other types of fluid connectors are also contemplated by the present invention. 
     Alternative means for establishing the liquid nutrient flow  14  are also contemplated. For example, a pump may be located near the upper portion  22  of the columns  20  to pull the liquid nutrient  12  from the nutrient supply module  10 . The tubes  18  do not have to be inside the columns  20 , but may connect the nutrient supply module  10  to the upper portion  22  of each of the columns  20  on the outside of the columns  20 . The present invention contemplates such other means for establishing the liquid nutrient flow. 
     In the embodiments illustrated, a plurality of growth sites  30  are located on each column  20 , such growth sites  30  being radially disposed about the longitudinal axis  40  and generally equidistant from the longitudinal axis  40 . As illustrated, the growth sites  30  generally face towards the internal space  42 . This provides generally equidistant lighting in the embodiment shown to all plants in the growth unit when a tubular light source is vertically supported along the longitudinal axis  40 . 
     There may be one or more growth sites  30  on each column  20 . Where there is more than one growth site  30  on each column  20 , the growth sites  30  may be vertically spaced apart on the columns  20 . 
     The growth sites  30  may be equidistant from the longitudinal axis  40  for equidistant lighting, even where the columns  20  themselves are not equidistant from the longitudinal axis  40 . However, in some embodiments the present invention also contemplates a growth unit where the growth sites are not equidistant from the longitudinal axis  40 . 
     Where at least some of the growth sites  30  are vertically spaced apart on the columns  20 , those growth sites  30  which are at generally the same vertical level may be equidistant from the longitudinal axis. This may provide advantageous lighting conditions to all the plants where, for example, a single bulb, located along the longitudinal axis, is used as a lighting source. In such a growth unit, the growth sites vertically further away from the bulb may be situated closer to the longitudinal axis than those growth sites vertically closer to the bulb, in order that all plants receive equidistant lighting for advantageous conditions. Those growth sites at the same vertical level may therefore be equidistant from the longitudinal axis, when even where not all growth sites in the growth unit are equidistant from the longitudinal axis. A variation in the distance of the growth sites from the longitudinal axis may be accomplished by tilting the columns or designing the columns to vary in distance from the longitudinal axis. Alternatively, the growth sites may protrude from the columns at different lengths, varying the distance of the growth sites at different vertical levels to the longitudinal axis. 
     The growth sites  30  in the embodiments illustrated in FIGS. 1 through 6 protrude upwardly from the columns  20  in order to facilitate anchoring plants at the growth sites  30 . The growth sites  30  in the embodiments illustrated angle upwardly at approximately a forty-five degree angle. The growth sites  30  may protrude from the columns  20  at alternative angles, however the angle will preferably be chosen as one appropriate to maintain plants in growth sites. The present invention also contemplates a growth unit where the growth sites  30  do not protrude from the columns  20 . 
     In the embodiments shown in FIGS. 1 through 6, the growth sites  30  form a unitary part of the columns  20 , the entire structure being formed from plastic or another suitable material. The invention also contemplates a growth unit where the growth sites  30  are not formed as a part of the columns  20 , but are later attached to the growth unit as separate components. 
     The growth sites  30  shown in the illustrations have circular openings  32  into which plants may be anchored and grown. The present invention is not limited to growth sites which have circular openings for receiving the plants. The growth sites may take various forms which would allow for a plant to be grown. For example, the various shapes and sizes of planting pots as normally found in the field of gardening may be used as growth sites, the size being limited of course by the size of the growth unit. Accordingly, a wide variety of types of growth sites that could be used in growth units are contemplated by this invention. 
     In the embodiments shown in FIGS. 1 through 6, the growth unit includes baskets  34  which fit into the circular openings  32  of the growth sites  30 . As shown in FIG. 6, the baskets  34  may be designed to hold plants  36 . The baskets  34  may be made of plastic or another suitable material. In the embodiment shown, the baskets  34  are open weave baskets. The plants  36  sit in the baskets  34  and the plant roots  38  protrude through the bottom of the baskets  34 . The present invention also contemplates other means for retaining the plants in the growth sites. For example, the columns  20  may contain a planting medium in the longitudinal passage  26  into which the plants may be anchored and grown. 
     Each growth site  30  may be positioned to contact the liquid nutrient flow  14 . The plants  36  may be located in the baskets  34 , which are placed in the growth sites  30 , and the plant roots  38  protrude from the base of the baskets  34 , as illustrated in FIG.  6 . The plant roots  38  are therefore located within the longitudinal passage  26  of the column  20 . As the liquid nutrient flow  14  is established through the longitudinal passage  26 , the liquid nutrient flow  14  will come into contact with the plant roots  38 . 
     There are other means for positioning the various types of growth sites such that the plant roots will come into contact with the liquid nutrient flow as it passes through the longitudinal passage of the columns. For example, where the longitudinal passage contains planting medium into which the plants are anchored at the growth sites, the roots of the plants will come into contact with the liquid nutrient flow as it travels through the planting medium. 
     Various types of liquid nutrient  12  may be used. The liquid nutrient may contain essential elements needed for plant growth, such as Nitrogen, Phosphorus, Calcium, magnesium, Sulphur, Iron, Potassium, Boron, Manganese, Zinc, Copper, and Molybdenum. For example, GGold Nutrient Line™ or General Hydroponics Flora Line™ contain these essential elements needed for plant growth and therefore may be used as the liquid nutirent. The quality, quantity and type of liquid nutrient used will vary depending on many factors, such as the type and age of the plants being grown. The liquid nutrient should be chosen with a view to establishing advantageous growth conditions. 
     Referring to FIG. 7, a plant growth unit according to an alternative embodiment of the invention is shown. The plant growth unit includes a nutrient supply module  50 , a single column  60  and a plurality of growth sites  70  supported by the column  60 . As described above, the nutrient supply module  50  is designed to contain a liquid nutrient  52  and, as in the embodiment shown, may act as a base for the growth unit. The nutrient supply module  50  may take on various shapes and various modes of manufacture, as outlined above. 
     As shown in FIG. 7, the single column  60  is disposed radially about a central vertical longitudinal axis  80  and defines an internal space  82 . This may be accomplished by wrapping the column  60  around the longitudinal axis. In the embodiment illustrated, the column  60  forms a uniform helical structure. The column  60  may, at all points, be generally equidistant from the longitudinal axis  80 . However, the present invention contemplates many various forms that the column  60  may take in order to dispose itself radially about the central longitudinal axis  80  and define an internal space  82 . The column  60  need not vertically rise in a uniform manner and all portions of the column  60  need not be equidistant from the longitudinal axis  80 . 
     The internal space  82  in FIG. 7, as with the previously described embodiments, may be adapted to accommodate a light source. A variety of light sources may be used, as described above. 
     The column  60  may have an upper portion  62 , a lower portion  64  and a longitudinal passage  66  through which the liquid nutrient may pass. As described above, the column  60  may be made of a variety of materials and constructed in a variety of ways. Further, as also described above, the longitudinal passage  66  may be empty or contain a permeable material through which the liquid nutrient  52  may pass. 
     The column  60  may be in fluid communication with the nutrient supply module  50  for circulation of a liquid nutrient flow  54 . In the embodiment shown in FIG. 7, a pump  56  circulates the liquid nutrient from the nutrient supply module  50  through a tube  58  to the upper portion  62  of the column  60  and through the longitudinal passage  66  to the lower portion  64  of the column  60 . As described above, various pumps  56  and tubes  58  are contemplated, as are other methods of establishing the liquid nutrient flow  54 . 
     In an embodiment of the invention including a single column  60 , a plurality of growth sites  70  may be located on the column  60 . The growth sites  70  are radially disposed about the longitudinal axis  80  and the growth sites  70  generally face towards the internal space  82 . In the embodiment shown, the growth sites  70  are located equidistant from the longitudinal axis  80 , resulting in equidistant lighting to all plants in the growth unit when a vertical light source is supported along the longitudinal axis  80 . Though the growth sites  70  may be equidistant from the longitudinal axis  80 , as described above, the growth sites need not be equidistant from the longitudinal axis. In alternative embodiments, only those growth sites at generally the same vertical level may be equidistant from the longitudinal axis. 
     As also discussed above, in embodiments such as illustrated in FIG. 7, the growth sites  70  may or may not protrude from the column  60 , and may do so at various distances and angles. The growth sites  70  may be of various shapes and sizes, and the growth unit may use various means for anchoring the plants in the growth sites  70 . The growth sites  70  may be positioned to contact the liquid nutrient flow  54  in the various ways described above and there are various options for the liquid nutrient to be used. 
     The present invention also contemplates a method for growing plants where a plant growth unit as described above is provided, plants are planted into the growth sites and a liquid nutrient flow is established. 
     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.