Starting Seeds in Soil Blocks

Seedling in 3/4" soil block.

 Friday afternoon I finally took some time off from working to get my seeds started. 

I started leeks, kale, eggplant, onions, lettuce, spinach, beets, lavender, marjoram, sage, parsley, thyme, rosemary, oregano and petunias, totaling 800 plants. This year I am not only starting seeds for our own garden, but also for the school garden and for a seedling sale to raise money for the school garden, so this is about a third of what I am planning to start.

Several years ago I started using soil blocks instead of seed starting trays to start all my seeds. I have had much better results with this method and it is much cheaper because I don't have to buy starting trays or peat pots each year.

To make soil blocks you need special tools called a soil block maker.

 The soil block makers come in different sizes, 3/4", 1-1/2", 2" and 4". The smaller 3/4" blocks are perfect for starting small seeds like lettuce, kale, herbs, etc, and the larger blocks work well for starting larger seeds like cucumber and squash. Soil block makers are available from several gardening stores such as Johnny's and are reasonably priced.

 Johnny's also has a video showing how to use a soil block maker.

There are soil mixes available specifically for use with soil block makers which I have used in the past, but I have had much better results mixing my own using my own compost.

The first thing I do is sift some of my compost with a fine screen to take out most of the stones, sticks and leaves.

After sifting, I am left with very fine compost and a little soil. The compost will absorb moisture, help hold the block together and supply nutrients to the emerging seed.

 The next step it to mix in a little water with the sifted compost. You don't want a soaking wet mix, so just add enough water to make a cement like mixture. If you take a handful of mix and squeeze it in your hand you want it to stick together without a lot of water coming out of it.

Once you have your mix ready, you will use your soil block maker to make your blocks.

3/4" soil block maker - makes 20 blocks.

You simply push the maker into the mix, push it around to fill it with soil, and then press it out into your trays using the handle. The soil block maker creates a little dimple in the center of the block for the seed. I simply place a seed in the center of each block and tap it in using my small dibble, making sure it has good contact with the soil.

I use old lettuce containers from the grocery store. They are the perfect size, they hold 80 3/4" blocks each and make little greenhouses when closed.

I put them directly on my heating mats and keep them closed until the seeds start to germinate and the leaves start to form.

The concept behind using soil blocks is simple. 

The seeds are planted in the shallow dimple and are not covered by soil. Seeds started this way germinate faster because they have plenty of oxygen. Once the seedlings started in the smaller blocks have their first true leave, they are "blocked up" to the next larger size soil block. The 1-1/2 and 2" block makers form a 3/4" square hole in the block, allowing you to just pop in the 3/4" blocked seedling  without disturbing the roots.

Cucumber seedling in 3/4" soil block.

2" soil blocks with 3/4" dimples.

The roots will continue grow to the outer walls of the block and then stop. When the roots reach the edge they have ample air, water and nutrients so they will now send their energy into growing the plant which results in healthier seedlings. The plants will not become root bound like they do when using peat pots or plastic pots.

Basil seedling in 2" soil block. Notice how root growth stops at edge of block.

When planting the seedlings into the garden you simply make a hole large enough to fit the soil block and plant it into the garden. Planting this way doesn't cause stress to the plants because you are never disturbing the roots. By using soil blocks to start my seeds I have much higher germination rates, faster germination and healthier plants.

These seeds were started Friday afternoon and Saturday morning they have already begun to germinate!

Kale seeds beginning to germinate.

Lettuce seeds emerging.

Lettuce in 2" soil blocks (photo taken last spring)

Shared at:

Deborah Jean's Dandelion House
Tilly's Nest 
The Backyard Farming Connection 
Eat, Make, Grow

Bert and Ernie - just a year ago!