Soil Blocks for Seed Starting

One of the biggest drawbacks to seed starting can be all the transplanting that is required.  Starting the seeds in flats, moving the seedlings to bigger pots, then bigger pots, or into the ground, can be a lot of work.  In addition, the transplanting can also be hard on the tender young plants, increasing seedling mortality.  One way to avoid damaging your new sprouts, and saving time and energy yourself is to start seeds in soil blocks.  What the heck is a soil block?  A soil block is compressed soil that has a depression in it, in which the seed is placed.  By creating seed blocks, the roots will never be cramped or confined, which occurs even with biodegradable peat pots and newspaper pots, transplant shock will be almost totally diminished, and you cut a few more plastic pots out of your life.

Starting seeds in seed blocks could be a great technique to use with winter seed sowing.  By starting the seeds in the blocks, outside in mini greenhouses, you will create strong plants AND reduce transplant shock even further.

Here is what you need to get started:

Soil (see recipe below)

Block maker.  You can make this easily with a few tools, and household items (directions below).

Something to hold your soil blocks in. These could be anything from shallow wooden crates, those clear plastic boxes that lettuce comes in, seed flats, or whatever else works.

Making the Block Maker:

You need:

For most projects a small yogurt cup and lid will work great. This will be used to make the actual block. Other mold materials could be PVC pipe, or other containers.

8 inch eye bolt, 3/8 inch wide.

2 bolts, each 3/8 inch.

2 washers

Drill with 3/8 inch bit.


To make the blocker:

With a hacksaw cut the bottom off of your yogurt container about 1/4 inch from the bottom. The part that you cut off will become the “plunger” that pushes the soil block out of the mold.

Make sure that the cut you made is straight and smooth all the way around.  If you need to bend any curved in areas, do so with a wrench.

In the center of the cut off bottom piece, drill a hole.

Place your eye bolt in the hole with a washer and nut on both sides of the hole, securing the eyebolt.  This will be the “plunger” that pushes the soil out the mold.  The nut on the bottom will make the depression that the seed will be planted in.  If you want to make a deeper hole, then simply add more nuts.

Seed Block Soil Recipe (from VelaCreations):

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.

You can also use a commercial seed starter.

Thoroughly wet the soil mixture before getting started with making the blocks.  You want it to be nice and wet so that the it will easily mold into the blocker and be released into the appropriate shape.  Think-sandcastles.

Jab the block mold (yogurt container) into the wet soil mixture.

Place the filled mold over the spot you want to release it (tray, crate, or whatever).

Use the “plunger” and push the soil out of the mold, into place.

Place the soil blocks fairly close together, about 1/4 inch or so.

Place a seed or two in each center depression and cover with soil.

Water gently with a fine mist so that you don’t flood the blocks and flatten them.


Some great resources for further reading and instruction:
Photo credit

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