I have had a love affair going on with soil blocking since 2020. Every year I improve my methods, tweak my soil recipe and have better and better success with it! So far I haven’t come across seeds that don’t enjoy starting by this method.
Soil blocking is a great way to start seeds because it is super sustainable. It’s also much easier to transplant seedlings from convenient little blocks without having to pull or squish them out of plastic squares. Learn the basics of soil blocking here so that this season you can easily start seeds without the mess of plastic trays!
What is Soil Blocking
Soil blocking is simply a method of using a special tool to create self-contained blocks of soil that you can start your seeds in. No pots or plastic at all, just soil! The key is to find the size soil blocker that you like and a seed-starting soil mix that is equal parts nutritious and light, but also holds shape. Don’t worry, I have a recipe for you!
To soil block, you will need:
- A soil blocker tool
- A tray for the soil blocks to go in
- Seed starting soil
How to Soil Block
Soil blocking is becoming super popular lately because of the ease it provides for gardening. Using a mold to form blocks of soil leads to no use of pots at all!
There are two main sizes: 1/4″ blocker (makes 20 1/4″ blocks), and 2″ blocker
You set blocks on trays like these and these and seed right into the blocks. The 1/4″ size can be used to start small seeds and then you bump the seedlings up to the 2″ block after they’ve grown a few leaf sets. The molds are it very easy to bump up. Or you can sow bigger seeds like squash right into the 2″ size.
Benefits of Soil Blocking
There are quite a few benefits to soil blocking beyond the ease of use it provides:
- air-pruning roots = stronger root systems
- no plastic waste
- cheaper because you’re not buying plastic trays, pots and 6 packs every year. Just buying soil.
- bottom watering makes strong root systems
- saves a ton of space when seed starting
- easier for transplanting
Best Soil Mix for Soil Blocking
The key to great soil for soil blocking will be getting a good, loamy consistency, a soil mixture that holds water and holds its shape, but also drains quickly. You’ll need to get your hands dirty and test this out, you want sticky, but not muddy soil.
Here is a recipe that I have had success with for the past few years:
Soil Block Recipe
For 24 cups (makes approximately 500 mini 3⁄4” blocks or 36 of the 2” blocks)
- 16 cups sifted compost (I like Happy Frog or Vermont Compost)
- 8 cups Pitt Moss or Coconut Coir
- 1 cup powdered Greensand
- 1⁄2 cup Rock Phosphate powder
- 1/4 cup Biochar and Mycorrhizal Fungi powder
Mix these ingredients dry.
Best Practice for Soil Blocks
Here are some of my best suggested practices for creating and using soil blocks:
- Prioritize using a high-quality, well-draining soil mix that is suitable for soil blocking. It’s essential to have a mix that offers good moisture retention and aeration.
- Ensure the soil mix is properly moistened before starting to make soil blocks, but mix the soils dry before that. You want it to be damp enough to hold together when squeezed but not overly wet.
- When using a soil block maker, firmly press the soil mix into it to ensure the blocks hold their shape well without being too compacted.
- Carefully remove the soil blocks from the block maker, handling them gently to avoid damaging the delicate structure.
- Place the soil blocks on a flat surface or tray for ease of handling and watering throughout the seed starting process.
- Consider watering soil blocks from below by placing them in a shallow tray of water. This method helps prevent disturbance to the seedlings’ roots.
- Provide adequate warmth and light for the soil block seedlings to encourage healthy growth and development.
- Choose the appropriate size soil block maker for the seeds you’re starting. Smaller blocks work well for tiny seeds, while larger blocks are suitable for bigger seeds or transplants.
- Maintain consistent moisture levels in the soil blocks, being careful not to overwater, which can lead to issues like damping off.
- Once the seedlings have developed strong roots and are large enough to handle, transplant them into larger containers or directly into the garden.
I also suggest reading this blog post for even more awesome tips on soil blocking.
Happy blocking!
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