One of the best systems we have seen to avoid transplant mortality is soil blocks. They have many advantages, but the main one is that soil blocks GREATLY reduce transplant shock, leaving you with more survivors in your garden. They won’t create root balls like starter pots or trays, they don’t limit roots in the soil like peat or paper pots, and they don’t destroy roots like flats.
Making soil blocks requires a soil block maker, or blocker. The blocker compacts soil into plugs that come with a preformed depression for placing your seeds. Getting your plants off to a good start has never been easier!
You can make these blockers any size you want, depending on the size of the seeds you have. A 2” block (½ pint size) is best for most seeds. We like the 4” size of the quart can for large seeds like squash and beans. Smaller blocks are good for starting faster growing, smaller seeds like lettuce, greens, and onions. If you go with a smaller can, you’ll want to reduce the size of the eye hook as well, probably making it 3-6 inches long.
The main thing with the can selection is avoiding a corrugated can, like a soup can, as the soil doesn’t release well. Make sure you clean the can well before starting.
Many soil mixes will work for a soil block, but this recipe will be almost fool-proof. A unit can be any sort of can or bucket, depending on the size of the mix needed (start small). There are lots of different recipes online, so feel free to experiment. You can also buy commercial mixes, though I have no experience with them.
Eliot Coleman’s Organic Recipe
30 units peat
1/8 unit lime or ½ unit wood ashes,
20 units coarse sand or perlite
3/4 unit organic fertilizer (equal parts blood meal, colloidal phosphate and greensand)
10 units good garden soil
20 units well-aged compost
Sift all ingredients before mixing. Mix the peat and lime or wood ash first. Mix the sand or perlite with the fertilizer. Then mix everything together.
Almost every single part of your blocker can be salvaged. Paint cans, medicine bottles, or just about any smooth container can work. The eye bolt serves as a handle, and you could just as easily use a long bolt with a wooden handle. The bakery containers are convenient, as they come with clear lids and are small and reusable.