Plant growing frame

In combination, a plurality of formstable blocks of plant growing substrate and a frame supporting said blocks therein in spaced relation to control root growth out of said blocks by root air pruning and thereby prevent root growth from one block to another;

• each said block having a top, a bottom and side surfaces, said top, bottom and side surfaces being penetrable by roots to thereby enable air pruning to occur;
• said frame comprising a planar network of criss-crossing horizontally extending spaced double rib members defining a plurality of air-passage-forming openings and a plurality of vertically extending open-ended block-receiving openings for receiving said blocks therein, the space between said double rib members defining said block-receiving openings and the space between each rib of said double rib members defining said air-passage-forming openings, said air-passage-forming openings encircling each block-receiving opening and separating each block-receiving opening from all neighboring block-receiving openings by said air-passage-forming openings;
• said rib members defining said block-receiving openings having planar surfaces for frictionally engaging portions of said side surfaces of said blocks to securely hold said blocks in said block-receiving openings to that said blocks do not fall out of said block-receiving openings during handling of said frame, with the entirety of said side surfaces of each said block being spaced from side surfaces of all neighboring blocks;
• vertical air passages defined between the spaced side surfaces of neighboring blocks and extending vertically through said air-passage-forming openings, whereby said vertical air passages extend vertically upward along the entire height of each block to its top;
• said vertical air passages completely encircling each block and isolating each block from other blocks by an air space which is of a size sufficient to control root growth out of the blocks by air pruning and prevent root growth between one block and another;
• said portions of said side surfaces which said planar surfaces of said rib members securely engage comprising only a small fraction of the surface area of said side surfaces of the block so that a remaining greater fraction of the surface area of said side surfaces is open to said vertical air passages;
• and
• said blocks being securely supported in said frame with an air space under the bottom of each block in communication with said vertical air passages so that the bottom of said block is open to the vertical air passages and air may flow uninterrupted from the air space under the bottom of each block, upward along said side surfaces of each block via said vertical air passages to the top to promote air pruning.