What is soil blocking and how does it work?

Soil blocking is a method of propagating seedlings that involves filling a metal blocking tool with soil and squeezing to form a compressed cube. Each cube is placed on a tray that is then bottom watered or misted regularly. Seeds are planted directly into the formed block. They come in various sizes and each cube fits perfectly into the next size up, making it easier when it is time to bump small seedlings up.

When seeds are planted into plastic pots, they often become root bound and will suffer transplant shock. Soil blocks are surrounded by air and will never become root bound because they will self-prune their roots. Air pruning occurs in soil blocking when the root systems start to grow out toward the drier soil and air surrounding the outer layer of the block. Once the roots reach the air, they stop growing. The exposure to air tells the plant to send out secondary roots, creating more extensive roots with more surface area to absorb water and nutrients.

What are the benefits of soil blocking?

Soil blocking is an eco-friendly, lower waste method of seed starting and when done right, can establish stronger and healthier seedlings that quickly acclimate after transplanting due to limited chance of shock. Due to their small size and the ability to place many on one tray, soil blocks are advantageous for growers with limited space. They significantly reduce single use plastics in seed starting and the soil blockers will not break down in the sun.




Happy Gardening,

Leigh Gradiz

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