What’s a cheaper, easier, and surprisingly more efficient way to start your seedlings? Soil blocks! If you’ve never used them before, read on to find out how soil blocks work, how you make them, and what advantages they offer over traditional pots and trays.
The following is an excerpt from The New Organic Grower by Eliot Coleman. It has been adapted for the web.
How Soil Blocks Work
A soil block is pretty much what the name implies—a block made out of lightly compressed potting soil. It serves as both the container and the growing medium for a transplant seedling. The blocks are composed entirely of potting soil and have no walls as such. Because they are pressed out by a form rather than filled into a form, air spaces provide the walls. Instead of the roots circling as they do upon reaching the wall of a container, they fill the block to the edges and wait. The air spaces between the blocks and the slight wall glazing caused by the block form keep the roots from growing from one block to another. The edge roots remain poised for rapid outward growth. When transplanted to the field, the seedling quickly becomes established. If the plants are kept too long in the blocks, however, the roots do extend into neighboring blocks, so the plants should be transplanted before this happens.