a cover 10 for a plant growing medium is shown in fig1 and 2 . the cover 10 is constructed from a suitably rigid material such as plastic . the cover 10 has a sheet 20 . the sheet 20 may be of any shape or size so as to cover the surface or surfaces of a plant growing medium that are directly exposed to light sources of the type frequently used for indoor growing . in the embodiment shown in fig1 and 2 , the sheet 20 is square . preferably , the sheet is substantially planar . further , the sheet 20 has four edges 22 , 24 , 26 and 28 . the four edges 22 , 24 , 26 and 28 meet at four corners 30 , 32 , 34 and 36 . the sheet 20 defines an aperture 40 . the aperture 40 may have any shape or size . in the embodiment shown in fig1 and 2 , the aperture 40 is circular . the aperture 40 shown in fig1 and 2 is orientated at the centre of the sheet 20 . it will be apparent to a person skilled in the art that it is not necessary for the aperture 40 to be orientated at the centre of the sheet 20 . the aperture 40 may also be in a different position in the sheet 20 such as near one of the edges 22 , 24 , 26 or 28 of the sheet 20 or near one of the corners 30 , 32 , 34 or 36 of the sheet 20 . at least one protrusion projects from the sheet 20 . in the embodiment shown in fig1 to 3 , there are four protrusions 44 projecting from the sheet 20 . it will be apparent to a person skilled in the art that the objects of the invention may be satisfied by any number of protrusions projecting from the sheet 20 and embodiments incorporating one or more protrusions are contemplated . as seen in fig1 , each protrusion is barrel - shaped with bevelled walls . the bevelled walls of the protrusion may meet at a point ( not shown ). in the embodiment shown in fig1 and 2 , each protrusion has a surface 60 . preferably , each of the surfaces 60 is parallel to the plane of the sheet 20 . the protrusions are each orientated proximate to a separate corner of the sheet 20 . a preferred embodiment of the protrusions 44 is shown in fig1 and 2 . protrusions having other shapes and orientations are contemplated . as seen in fig2 , each of the protrusions 44 is hollow . it will be apparent to a person skilled in the art that the objects of the invention may be achieved if the protrusions are solid and this is contemplated . as seen in fig1 and 2 , in a preferred embodiment of the cover , four walls 62 , 64 , 68 and 72 are integrally attached to edges 22 , 24 , 26 and 28 , respectively . in the embodiment shown in fig1 to 3 , each of the walls 62 , 64 , 68 and 72 is in a plane perpendicular to the plane of the sheet 20 . each of the walls 62 , 64 , 68 and 72 has a flange 80 at an end of the wall opposite to the end of the wall that is integrally attached to the sheet 20 . in a preferred embodiment , each of the walls 62 , 64 , 68 and 72 opposes one of the other walls . as seen in fig1 , two of the opposing walls 62 and 68 define a slit 90 . in a preferred embodiment , each of the slits 90 is elongated and positioned in the centre of the wall . each of the slits 90 enhance the circulation of air proximate to the plant growing medium . each of the walls 62 , 64 , 68 and 72 has a number of ridges 100 . each of the ridges 100 extend from a point at which the flange 80 meets the walls 62 , 64 , 68 and 72 beyond a point at which the edges 22 , 24 , 26 and 28 of the sheet 20 meet the walls 62 , 64 , 68 and 72 . from the inside of the cover 10 , each of the ridges 100 is convex or bowed outward . further , the ridges 100 are parallel to one another and the ridges 100 other than the ridges 100 orientated where the walls 62 , 64 , 68 and 72 meet are equidistant from one another . each of the slits 90 bisect one or more of the ridges 100 . as seen in fig3 , in operation , the cover 10 is placed upon a plant growing medium 110 . the plant growing medium 110 can be any suitable medium for growing plants including soil and rockwool . the shape and dimensions of the cover 1 0 must be such that the cover 10 fits on the plant growing medium 110 . specifically , the distance between opposing walls 60 and 68 of the cover 10 must be greater than the distance between opposing walls 112 and 114 of the plant growing medium . when the cover 10 is placed on the plant growing medium 110 , the surface 60 of each protrusion engages a top surface 116 of the plant growing medium 110 . for optimal performance , when the cover 10 is placed on the plant growing medium , none of the walls 62 , 64 , 68 or 72 of the cover 10 should engage the plant growing medium . in a preferred embodiment , each of the walls 62 , 64 , 68 and 72 is positioned in a plane parallel to a plane of the walls of the plant growing medium 110 upon placement of the cover 10 on the plant growing medium 110 . numerous modifications may be made to the embodiment described above without departing from the scope of the invention which is defined by the claims .
the present invention relates to a device for covering a plant growing medium . the device includes a sheet that defines an aperture . one or more protrusions extends from the sheet to engage a top surface of the plant growing medium . a wall is integrally attached to each edge of the sheet . each wall has a series of ridges .