Welcome to Bepa's Garden!
This blog is about organic gardening, healthy eating and healthy living.
Each month I will be posting Garden To-Do Lists, Tips & Techniques, Garden Project Plans, Photos from the Garden, Recipes and Book Reviews.
I hope you enjoy reading and I hope I can inspire others to start a backyard garden!
Happy Gardening!

Tuesday, March 22, 2011

Starting seeds with soil blocks

Pepper seedling in 3/4" soil block

A few years back  I started using soil blocks for starting seeds after becoming discouraged by the low germination rates I was getting using plastic propagation trays. Soil blocks are easy to make, eliminate the need to buy pots, take up lees space and provide extremely high germination rates!

3/4" and 1-1/2" soil block makers

Soil block makers come in 3 different sizes - 3/4", 1-1/2" and 4". You can make your own soil mix or purchase specific soil block mixes. Smaller seeds are started in the 3/4" soil blocks.When the seedlings germinate and the roots start to grow out of the blocks you "block up" to the next size. The 1-1/2" maker has 3/4" square dibbles to allow the 3/4" blocks fit perfectly into them.

1-1/2" and 3/4" soil blocks

The compact soil blocks stay together so they are easy to handle. The roots will grow to the outside edges of the blocks and develope a healthy root system. In the photo above you can see the roots of the cucumber in the 3/4" block on the right coming out at the bottom. The soil blocks can be placed directly on the heating mats, but I use recycled lettuce containers from the grocery store. Each container holds 80 - 3/4" blocks and creates a mini-greenhouse preventing the blocks from drying out too quickly.

Recycled lettuce containers, each holds 80 - 3/4" soil blocks

When planting in the soil blocks, I place the seed in the dimple created by the block maker and tap each seed in making sure it has good surface contact. I don't cover with a layer of soil becasue the seeds seem to germinate better when exposed to air. I get 80%  to 100% germination rates using this method. Seeds seem to germinat quicker - the photo below of cucmber seeds was taken 2 days after planting, every seed germinated (the 2 blocks in the lower right hand corner weren't planted).

Cucumber seedling in 3/4" soil block

Johnny's Seeds has a great video that explains soil block makers in more detail and shows you how to use them. Another excellent resource is Eliot Coleman's book The New Organic Grower. Eliot goes into great detail explaining how to plant in soil blocks, why they work so well and even shows you how to make your own soil block mix. The New Organic Grower has become one of my most valuable tools in organic gardening. 


  1. Have you had any problems with algae growth on the tops of the mini blocks? We've been trying everything from keeping them uncovered during the day to allow more air circulation, to not watering them as much...Help?

  2. Amanda,
    I haven't had a problem with algae. It sounds like too much water. When I start my seeds I put the small soil blocks in the plastic lettuce trays (shown in the photos), set them on heating mats and keep them in the dark until the seeds start to germinate. I keep the lids closed, but not tight, and I water using only a spray bottle, misting the blocks. I keep the blocks moist, but not soaking wet. When the seeds start to germinate and the leaves start to form I turn on the grow lights or move them out to the greenhouse if it is warm enough. As soon as roots appear at the bottom of the block I "block up" to the next size and put the blocks in trays. I only water heavy if the soil blocks seem to be drying out too fast. Hope this helps.

  3. Where were you and this post last March when I was planting my seeds in plastic trays? Ugh... I am going to start getting ready for planting in soil blocks for this year... and, I'm saving my lettuce containers as well... thank you for yet another helpful post Rob~

  4. I'm experimenting with soil blocks this year. I've been following Eliot Coleman's advice by not covering the seeds with soil, but some of the seedlings appear to be poorly anchored. Do you have any problems like that? Maybe I'll try tamping them down a bit like you said. (This could also be because they aren't getting enough light and putting all their energy into growing up rather than down. I've purchased a grow light to address the lack of winter sunshine this year.)

    1. I used to get seedlings that would germinate on top of the smaller blocks but I started making a little deeper hole in the blocks with my small dibble and them lightly tapping each seed in so it makes contact with the soil (not pressing it in). I also make sure I have the grow lights on as soon as they start to emerge. Doing this has made a huge difference. I will sometimes get a seedling or two that will grow on top of the block, especially with tomatoes if I don't block up in time, but I just gently transplant them in larger blocks and they are fine.
      Hope this helps.