If you’ve spent any time starting seeds, you’ve probably used plastic seed trays, peat pots, or even egg cartons. They’re handy, sure—but they also come with their fair share of drawbacks: root binding, transplant shock, and plastic waste, just to name a few. That’s where soil blocks come in. Once you try them, you might never go back.
What Are Soil Blocks?
Soil blocks are compressed cubes of soil that eliminate the need for pots entirely. Instead of planting seeds in containers, you plant them in soil itself. They hold their shape thanks to the right balance of moisture, compost, and structure—and they create an ideal environment for strong, healthy seedlings.
Why Use Soil Blocks?
1. Healthier Root Systems
One of the biggest benefits of soil blocks is air pruning. When roots reach the edge of a block, they stop growing instead of circling like they do in plastic cells. This results in a dense, fibrous root system that’s ready to take off when transplanted.
2. No Plastic Waste
Soil blocks cut out the need for plastic pots or trays. They’re a more sustainable option—especially if you’re looking to scale up your growing operation without drowning in disposable materials.
3. Minimal Transplant Shock
Because there’s no container to remove, seedlings go directly into the ground (or a larger block) with their roots undisturbed. This keeps stress low and transplant success high.
4. Efficient Use of Space
The blocks can be tightly packed together, making the most of every inch under your grow lights or on your heat mat. No more wasted space between pots.
How to Make Soil Blocks
What You’ll Need:
- A soil blocker (mini ¾-inch or standard 2-inch)
- A flat tray or solid surface
- A mixing tub or bucket
- Water
- A soil-blocking mix (recipe below)
Soil Block Mix Recipe:
You want a mix that holds together well but stays light enough for roots to push through. Here’s a basic recipe to get you started:
- 2 parts compost or worm castings
- 2 parts coco coir or peat moss
- 1 part perlite or sand
- 1 part garden soil or sifted topsoil
- Optional: a scoop of bone meal or kelp meal for nutrients
Add water slowly and mix until the consistency feels like wet brownie batter—damp enough to clump in your hand but not soupy.
Step-by-Step Instructions:
- Prep Your Area
Lay out a tray or a flat surface to press your blocks onto. - Wet the Soil Blocker
Dip your soil blocker into water first so the soil doesn’t stick. - Load It Up
Press the blocker into your wet soil mix, twisting slightly to compress the mix into the chambers. Make sure it’s packed tightly. - Release the Blocks
Place the blocker on your tray and press the handle to release the blocks. They should hold their shape and have little indentations on top for your seeds. - Sow Your Seeds
Drop one seed per block into the divot and cover lightly, if needed. - Keep Moist but Not Soggy
Water gently—bottom watering works great for soil blocks—and keep them under lights until they’re ready to transplant.
Tips for Success:
- Use a heat mat for better germination, especially in cooler climates.
- Start small. If you’re new to soil blocking, try the mini blocker for smaller seeds like lettuce or snapdragons.
- Label everything. When your blocks are packed tightly, it’s easy to lose track of what’s what.
Final Thoughts
Making soil blocks may feel like an extra step at first, but it pays off in healthier plants, less waste, and smoother transplanting. It’s a simple shift with a big impact—especially if you’re growing on a small scale or trying to minimize your environmental footprint.
Whether you’re growing cut flowers or vegetables, soil blocks give your seedlings the best possible start.