Coleman uses a soil block maker that he developed for Johnny’s Selected Seeds ($22 to $170 depending on the size). This is a mold that forms the wet growing medium into cubes. You can use different sizes to contain seeds of varying sizes.
Make a blocking mix that will hold together but not harden out of peat, sand, soil, and compost. Coleman uses the following recipe to make a large amount of mix at one time.
- Start with three 10-quart buckets brown peat.
- Mix in 1/2 cup lime.
- Add two 10-quart buckets coarse sand or perlite and 3 cups base fertilizer, and mix together.
- Add one 10-quart bucket soil and two 10-quart buckets compost, and mix thoroughly.
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A seed or cube pin makes the indentation to hold each individual seed or small seedling. You can use interchangeable types of pins for different plant varieties and sizes.
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Coleman recommends a modular system so that seeds can be started in smaller soil blocks that then fit into large blocks as they grow and require more root space.
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Place each small seed plug into the larger blocks until you have a full tray. Coleman recommends an open-sided tray so that the blocks are easy to scoot off for planting.
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Keep the soil blocks watered with a mister, fine rose can, or hose until planting time.
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The Four Season Farm greenhouse is full of dozens of healthy lettuce seedlings. And not a plastic pot in sight.