Abstract:
A seedling container and a method of making the same, that includes a sleeve filled with a compressed plant growth medium and having a first end, a second end, and a defining sidewall. The sidewall has at least one integrally formed tear away strip that extends between the first end and the second end. The tear away strip enables the sleeve to be readily removed to enable a seedling to be planted that is encased in plant growth medium.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a seedling container and a method of making the same. 
     BACKGROUND OF THE INVENTION 
     Canadian Patent 939,905 describes a seedling container having a body of compressed peat moss encased in a thin, tubular, impermeable, flexible casing, which encases the side surface only of the body of compressed peat. U.S. Pat. No. 4,245,431 describes an apparatus for making seedling tubes, such as those described in Canadian Patent 939,905. 
     When it comes time to plant a seedling that has been grown in the seedling container, as described above, the thin tubular casing is removed. This is a time consuming process, that requires the use of a cutting instrument. 
     SUMMARY OF THE INVENTION 
     What is required is a seedling container that will make planting seedlings a less time consuming process. 
     According to one aspect of the present invention there is provided a seedling container that includes a sleeve filled with a compressed plant growth medium and having a first end, a second end, and a defining sidewall. The sidewall has at least one integrally formed tear away strip that extends between the first end and the second end. 
     When planting a seedling that has been grown in the seedling container, as described above; the sleeve is removed from around the plant growth medium by tearing away the tear away strip to open up the sidewall. This procedure can rapidly be performed and does not require any cutting tools. The seedling, still encased in plant growth medium, can then be planted. 
     Although beneficial results may be obtained through the use of the seedling container, as described above, even more beneficial results may be obtained when several tear away strips in the form of ribs are used. The tear away rib strips serve as reinforcement allowing a thinner sidewall to be used. The rib strips also serve to direct root growth downward when the roots reach an interface between the plant growth medium and the sleeve. 
     According to another aspect of the present invention there is provided a method of manufacturing a seedling container, involving the step of co-extruding an inner stream of compressed peat moss and an outer annular stream of polymer plastic. This forms a continuous flexible polymer plastic sleeve filled with compressed plant growth medium. The continuous coextruded sleeve with compressed plant growth medium is cut into individual lengths each having a first end, a second end and a defining sidewall with at least one integrally formed tear away strip that extends between the first end and the second end. 
     This method of manufacture allows the seedling container described above to be manufactured in a continuous process at a comparatively high rate of production. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein: 
     FIG. 1 is perspective view of a seedling container constructed in accordance with the teachings of the present invention. 
     FIG. 2 is a side elevation view, in section, of a method of manufacturing a seedling container as illustrated in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment, a seedling container generally identified by reference numeral  10 , will now be described with reference to FIGS. 1 and 2. 
     Referring to FIG. 2, in accordance with the teachings of the preferred method, seedling container  10  is manufactured by co-extruding an inner stream of plant growth medium, such as peat moss  30  and an outer annular stream of polymer plastic  32 , thereby forming flexible polymer plastic sleeve  12  filled with compressed plant growth medium  14 . Peat moss  30  is driven in a direction shown by arrow  33  by a screw drive  34  through a nozzle  36  of a peat extruder  38  to form a core of continuous length of compressed peat moss  30 , with a substantially circular cross section. Molten thermoplastic, preferably polyethylene with low tear strength properties is extruded as outer annular stream of polymer plastic  32  from a plastics extruder  44  through a film forming die  46  in the same direction  33  as peat moss  30 . There is a slight differential extrusion rate between the output of peat moss  30  and molten plastic  32 . Peat moss  30  moves forward at a faster rate than molten plastic  32 , so that molten plastic  32  is drawn down onto the surface of peat moss  30  which produces a plastic sleeve  12  about a compressed plant growth medium core  14 . An air nozzle  47  cools and freezes the plastic sleeve  12  at the point at which it is drawn down to the diameter of the compressed peat moss core  14 . Once plastic sleeve  12  is cooled, peat moss core  14  is held tightly within sleeve  12 . It is important that the peat moss  30  used in the manufacture of seedling container  10  have adequate porosity and density to support plant growth. If the density is too high, the growth rate of seedlings grown in the resultant container will be adversely affected. There is a correlation between the level of moisture in the peat moss and its density. The density decreases as the moisture content increases. The moisture content is preferably within a range of 70% w/w to 84% w/w. Beneficial results have been obtained with a moisture content in a narrower higher end of that range of 78% w/w to 82% w/w. The peat moss must not be allowed to become too wet or too dry. If the moisture content rises above 84w/w % the peat moss no longer holds together. If the peat moss is dried to less than 40% of its original moisture content, its moisture holding capacity is degraded. 
     The continuous extrusion of peat moss  30  sheathed in polymer plastic  32  is cut into individual lengths to form seedling container  10  with a polymer plastic sleeve  12  filled with compressed plant growth medium  14  as illustrated in FIG.  1 . Referring to FIG. 1, seedling container  10  has a flexible polymer plastic sleeve  12  filled with compressed plant growth medium  14 , such as peat moss  30 . Sleeve  12  has a first end  16 , a second end  18  and a defining sidewall  20 . Sidewall  20  has several integrally formed tear away rib strips  22  that extend between first end  16  and second end  18 . Each seedling container  10 , is turned on end and a depression is made in plant growth medium  14  at first end  16 . A seed is placed in the depression and covered with sand to permit the seed to germinate and grow in seedling container  10 . Tear away strips  22  are, preferably, in the form of ribs which serve to direct root growth downward when the roots reach an interface between plant growth medium  14  and sleeve  12 . After an appropriate length of time, when the seed has germinated and the resultant seedling  24  has grown sufficiently robust, it is sent to the field to be planted. Just prior to planting the seedling, one of rib strips  22  is torn away to open up sidewall  20  of sleeve  12  permitting sleeve  12  to be removed and discarded. Seedling  24 , still encased in plant growth medium  14 , is then planted. 
     Seedling container  10  provides a number of significant advantages over the seedling container described in Canadian Patent 939,905. Seedling container  10  can be manufactured in a less labour intensive manner in a continuous manufacturing process at a higher production rate than was possible for the seedling container described in the 939,905 patent. The addition of the tear away strip  22  makes it easier to remove outer sleeve  12  without the necessity of using a knife or other sharp instrument. Tear away strips  22  are in the form of ribs, whereby root growth is directed downward when they reach an interface between plant growth medium  14  and sleeve  12 . In the absence of ribs to direct root growth downward there is a danger that as the seedling will be strangled by its roots as it matures in sleeve  12 . 
     It will be appreciated that although peat moss is used for illustration purposes, there are alternative plant growth mediums which may be used. For example, finely shredded bark or other natural fibrous materials may be used in place of peat moss if it does not degrade during the growing of the seedling. It will also be appreciated that other materials, such as pearlite or vermiculite, may be mixed with peat moss in order to increase porosity of the peat moss to accept more nutrient solutions at the root level. The addition of other material is permissible, as long as such additions do not interfere with the integrity of the plant growth medium when sleeve  12  is removed. 
     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.