Container for plants

An improved container for growing and holding plants for transplanting encloses the root ball in a polyurethane liner, which is then supported within a wire mesh outer basket. The polyurethane liner does not rot above ground, yet is permeable, so that the roots in the root ball air prune, forming extensive fine filamentary root growth, significantly improving the viability and health of the plant when transplanted. Although the liner of the invention does not rot above ground, it easily passes roots when the basket and root ball is planted, As a result, the basket and liner need not be removed prior to planting the plant, significantly simplifying handling of the plant.

BACKGROUND OF THE INVENTION 
This invention relates to the field of baskets or pots for potting nursery 
plants. Such containers hold soil or a growth medium, and serve to support 
and restrain the plant root structure from its initial sprouting through 
continued growth. The container also provides for ready transportation of 
the plant, and should provide for easy transplanting of the plant into the 
ground. 
U.S. Pat. No. 4,223,480 to Welty is the closest known prior art in regards 
to removable inner liner for potting a plant and transplanting the same. 
This patent discloses a perforated, sectionalized liner made of flexible 
material, folding upwards or away from a base member. A group of finger 
members permits the ready removal of the enclosed liner with its contained 
potting soil and root ball from a pot and the subsequent removal of the 
root ball from the liner. 
U.S. Pat. No. 2,960,798 to Linstaedt discloses a nursery pot constructed of 
an outer metal mesh reinforcing material and having, as a liner, tar paper 
(asphaltum felt). This construction provides an impermeable, decoratable 
pot. 
U.S. Pat. No. 4,106,235 to Smith discloses a two section, inner and outer 
pot construction where roots are intended to grow through the inner pot 
mechanism. However, this structure is designed specifically for 
hydroponics and utilizes a porous inner pot bottom (screen) through which 
the roots can grow into a hydroponic medium. 
U.S. Pat. No. 2,142,324 to Magyar, Jr. discloses a potting system in which 
a pot liner is provided with an inner and outer sleeve, rotatable to 
permit the plant roots to extend through the walls of the pot. The entire 
construction is rotated open for transplanting and planted, pot, root ball 
and all. The pot of this patent is therefore properly considered part of 
the root ball. 
U.S. Pat. No. Des. 250,940 discloses a visual depiction of a Plant 
Container having a spaced distance from an inner liner to the base of the 
container. 
U.S. Pat. No. Des. 255,555 likewise discloses a pot having an apparently 
porous inner liner spaced a distance from the bottom of the pot and 
additionally apparently includes tubes vertically ascending from the base 
of the pot through the screen into the upper, root ball area of the pot 
which are hollow and which have periodically spaced holes. 
U.S. Pat. No. 879,613 to Edwards discloses an early transplanting basket in 
which the root ball is suspended within a coarse metal mesh basket. The 
entire outer surface of the root ball is exposed to the air rather than 
just those root tendrils which penetrate through the lining. 
U.S. Pat. No. 4,027,429 discloses another form of pot in which an inner 
ring within the base of the pot creates a spaced annular water reservoir 
in the bottom of the pot upon which is placed, loosely, a soil supporting 
disk which supports the soil and the plant. The bottom of the pot is open 
and the disk can be pushed upward through the bottom of the pot to remove 
the soil or root ball for planting. 
None of these patents disclose a structure in which the soil is contained 
within a permeable soft plastic membrane, enclosing the root ball but 
through which the roots can grow, permitting roots to air prune at the far 
tips only without exposure of the rest of the root system within the root 
ball to air, the ball being supported within a wire basket which minimizes 
inhibition of root growth, but which supports the liner and its contained 
liner with root ball for free air circulation. 
SUMMARY OF THE INVENTION 
A container for starting plants intended to be transplanted is a 
combination of: 
A relatively squat, substantially open mesh external basket generally wider 
than it is high, and preferably with a taper, so that successive baskets 
may be nested in storage. 
The basket should have a false bottom, defining an open, air filled space 
between the bottom of that part of the basket which contains the root ball 
and the ground, or, in an alternate embodiment, it should have an 
impermeable bottom to prevent through growth of roots. 
A penetrable, water permeable liner within the basket, made of polyurethane 
foam. 
The device contains a potting medium within the liner in which a plant is 
started and grown. During growth, the roots of the plant will penetrate 
the lining and the basket, and will then air prune, an effect that occurs 
when the roots of a growing plant are exposed to air. This promotes 
fibrous hair roots, a desirable characteristic in a plant to be replanted. 
The relatively squat shape and open air space of the false bottom of the 
container creates more lateral root growth, which aids upright stability 
after transplanting. 
Such enhanced lateral root growth may alternatively achieved by providing 
an impermeable or root impenetrable bottom to the container, so that 
substantially all fine root growth is lateral. 
It is thus an object of the invention to provide a container for plants 
which enhances fine root growth. 
It is a further object of the invention to provide a container for plants 
which enhances lateral growth of roots. 
It is a further object of the invention to provide a container for plants 
which resists rotting while above ground. 
It is a further object of the invention to provide a container for plants 
which reduces incidence of root bound growth. 
It is a further object of the invention to provide a container for plants 
which enhances retention of soil in a root ball while directing and 
enhancing fine root growth. 
It is a further object of the invention to provide a container for plants 
which enhances fine root growth so as to make a plant more transplant 
shock resistant. 
It is a further object of the invention to provide a container for plants 
which may be transplanted intact, without inhibiting plant growth.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The drawings disclose and this description will concentrate on the 
preferred embodiment of the Plant Container of the invention; several 
significant variations are possible and will be discussed below. 
Referring to the Drawings, the Plant container 10 is used in Nursery 
practice to grow and sustain a plant 12 until it is transplanted into a 
final growing location in the ground. Such a container must contain a Root 
Growth Medium 14, typically soil 16 or a similar loose particulate 
compound, within which plant 12 grows by spreading its roots 18. The 
combination of Soil 16 and roots 18 is typically called a root ball 20, 
and the plant 12 is fertilized, watered, moved and ultimately 
transplanted, by handling the root ball 20. 
The Container 10 of the invention comprises an outer supporting means 30, 
formed as an open mesh construction wire basket 30, the wires forming 
interconnected vertical ribs 32 and horizontal rings 34 to form a basket 
that is typically round, arising from a bottom member 36, enclosing an 
interior within side member 38. This interior is formed to contain the 
Root Ball 20. 
Wire Basket 30 may be made of either corrosion resistant or corrosion 
susceptible wire; the wire may be either galvanized ferrous wire of 
plastic or epoxy coated wire, to resist corrosion. 
Alternately the basket 30 may be made of non-galvanized Ferrous wire. As 
the basket 30 is intended to be planted in the ground as part of the 
transplantation process, corroding wire is generally preferred. However 
some plants 12 require an extended above ground growing and storage time, 
and for such plants, a non-corrosive basket is preferred. The open mesh 
construction of the basket 30, with sizeable openings, and only sufficient 
wire for strength, prevents such a basket 30 from inhibiting or harming 
future growth of a plant, even though the basket 30 degrades slowly after 
being planted. 
The Basket 30 is lined with a permeable, root-penetrable liner means 44. 
This liner means has two functions: it retains the soil 16 within the 
basket 30 to form the root ball 20. More important, it is the means for 
enhancing root growth and propagation by enhancing air pruning of the 
roots 18 of the plant. 
Air pruning is a known phenomenon where a root within a root ball will not 
grow into open air. Air contact kills the tip of the root, which reacts by 
putting out many fibrous root extensions. Ultimately, air pruning produces 
a very dense, fibrous, hair root form of root ball. This produces a hardy, 
healthy plant, and makes survivability for transplanting very good. 
The liner means 44 must then have the strength to hold the soil 16 within 
the basket 30 despite its generally open mesh construction. It must permit 
free growth through itself of roots for air pruning, and it cannot choke 
off or cord the roots. Finally, while it must be permeable to permit 
watering of the plant and control of the moisture content of the root 
ball, it should be reasonably non-biodegradable so that it does not rot 
above ground. Rotting destroys the physical integrity of the root ball 20, 
and is a principal problem with burlap root ball coverings. 
It has been found that a polyurethane foam liner is particularly and 
uniquely suited to form the liner 44. The thickness of the foam is a 
function of the size of basket 30, with thicker foam required for strength 
with larger openings basket 30. Of the polyurethane foams, polyether 
polyurethane is preferred; it is also desirable that a UV resistant foam, 
commonly sold as "Blue Foam" be used in areas having intense sunlight. 
Basket 30 must further provide for air circulation or air flow 56 about the 
exterior 46 of liner 44 to promote air pruning. This may be as simple as 
placing basket 30 on spacing means 48 to provide air flow 56 about the 
bottom 36. Suitable spacing means could be blocks or timbers 50. 
Preferably, spacing means 48 would be integral to basket 30. A false bottom 
52 may be constructed in basket 30, by extending vertical ribs 32 in an 
internal loop. Alternately, separate wire ribs 33 may be interconnected 
within basket 30 to form false bottom 52. False bottom 52 then supports 
conformably liner means 44, creating a space for air flow 56 around the 
bottom exterior 46a of liner 44. 
In such construction it is desirable to promote lateral root growth for 
stability of the plant 12 when transplanted. This may be readily done by 
shaping basket 30 so that it is wider than it is tall; air pruning will 
then produce lateral root growth throughout the root ball 20, causing the 
root structure to follow the lateral, wide shape of basket 30. Tapering 
the sides 38 of basket 30 is advantageous, since it permits the baskets 30 
to be stacked for storage prior to use. 
There are circumstances where air pruning of roots on the bottom of the 
root ball 20 is undesirable. The basket 30 may be modified readily for 
this use by eliminating false bottom 52, and either covering bottom 
interior 36a with an impermeable, root-growth resistant material 50 or by 
covering the bottom exterior 46a of the container 30 with a removable 
material 50 which is root-growth resistant. 
In the first case, a solid, bio-degradable material may be used to cover 
the bottom 36a of the basket 30. Wood is a preferred such material, but 
either plywood, fiberboard or Masonite.TM. are suitable, as either will 
resist growth of roots, but will readily rot once buried for 
transplanting. The resulting container 10 will expose the liner 44 only on 
the sides, and the resulting root growth, with air pruning, will be 
lateral, producing a wide dense root ball 20. 
In the second case, the bottom exterior 46a of the basket 30 (which has no 
false bottom 52) will be covered with a root choking material 50. A 
tightly woven synthetic cloth will have the necessary plurality of small 
non-expandable openings to prevent root penetration by killing any 
penetrating roots by cording, a process analogous to girdling, where a 
plant is killed by circumferential pressure against its growth cells, 
which form the outer layer of the root. Some weave is necessary so that 
water may drain through the cloth; the weave must be tight so that no 
substantial opening exists through which a root may grow. The cloth should 
be synthetic, since natural materials (cotton, sisal, burlap, etc.) would 
rot and would then promote rather than hinder root growth. Such a cloth 
should be removed at the time of transplanting into the ground. 
A second form of root-growth resistant material 50 is that material which 
is not root choking, but is impervious to roots. Such materials include 
solid plastic sheet, preferably opaque or black plastic sheet, such as 
6-mil black plastic. One source is trademarked "Visquene". Alternately, 
Tarred Felt, either 15 pound or 30 pound weight, would be suitable. Other 
solid materials would be suitable, limited only by cost, and the ease of 
removing the material before transplanting. 
The container of the invention also reduces the plant becoming root bound, 
as the roots are not internally deflected during growth by a rigid or 
non-penetrable container wall. The root penetrates the liner, and is air 
pruned, not deflected back into the root ball. 
An alternate form of the invention is shown in FIGS. 11 and 12. In the 
field of transplanting trees, recent mechanical developments have led to 
the use of large digging machines which can remove a small sapling for 
transplanting by spading, in a single action, the entire sapling and root 
ball from the ground. Such Tree spades include designs by manufacturers 
sold under trade names such as Vermeer, Caretree, Big John and Burkeen. 
Such tree spades are in the form of segmented hydraulically powered 
digging spades which cut and pull a root ball in the form of a truncated 
cone having generally a 30 degree angle. 
Such mechanically spaded root balls may be in varying sizes ranging from 
small ornamental shrubs to large saplings. For any given tree spade, 
however, the size of the root ball is uniform and repeatable, and the 
shape of the root ball is that of a truncated cone having a 30 degree 
angle. 
Once spaded out of the ground, the root ball 20 is placed in a lined basket 
for holding above ground until transplantation. Each mechanically spaded 
root ball 20 is uniform in size and shape, as determined by the size and 
shape of the tree spade used. Since the resulting basket 30 is cone 
shaped, the liner 44 of the invention can be formed as two identical cone 
shaped segments 44a of polyurethane foam, which are then stapled or 
otherwise fastened together along their edges 64 for a distance; the 
bottom or tip 66 of the cone shaped segments 44a are not fastened. 
The resulting cone shaped liner 44 can then be placed in a supporting wire 
basket 30 by folding the tips 66, overlapping to each other, forming a 
cone shaped basket liner 44. 
The field dug plant is then placed in the inventive lined basket. An 
advantage of the mechanically spaded root balls and the basket is that 
there is no requirement to back fill the basket with potting soil, pine 
bark or other fillers; the uniform root ball permits exact fitting to the 
liner basket. 
When field growing and digging plants, timing becomes a problem. Digging of 
plants is usually done in the late fall or early spring season. 
Unfortunately, this is also the time when bad weather is most prevalent. 
The invention provides a liner which does not rot, even in the presence of 
excessive rain or temperature extremes. Thus plants can be dug whenever 
conditions, such as soil moisture and temperature, are good, and the 
basketed plant can then be held above ground without degradation. This 
provides an excellent improvement to mechanical field digging. 
As with the prior embodiments, the polyurethane liner does not rot so long 
as the plant is above ground, and the inventive liner promotes air pruning 
of the roots in the root ball. Plants have now been held for beyond two 
years above ground in baskets having the inventive liner without rotting 
or degradation of the liner or root ball; when planted the roots grow 
easily through the liner and basket, and thus the basket, as before, does 
not have to be removed before planting. 
The container of the invention may be readily transplanted. The 
polyurethane liner 44, while resistant to rot, may be safely buried as the 
roots will readily grow through it, and the liner residue is non-toxic to 
plants and to the environment. If the container 30 is of the alternate 
form with a wooden base, it may still be buried; the base will rot, 
freeing the bottom roots. If the alternate form is of the synthetic bottom 
cloth form, the cloth 50 will have to be removed before transplanting, but 
this is a minor task, and the container 30 with liner 44 will still 
maintain the physical integrity of the root ball 20. 
It should be apparent to those skilled in the art that the invention has 
disclosed a new and more useful plant container, which enhances root 
growth, resists rotting, and is readily moved and transplanted. It should 
be apparent that the invention is not limited to the specific embodiment 
shown in the drawings, but extends to the wider equivalents as claimed.