I may receive commissions from purchases made through links in this article. Please see my full disclosure policy for more information.
What’s a cheaper easier, and more earth-friendly way to start your seedlings? Soil blocks. If you’ve never used them keep reading to find out the benefits soil blocks offer over traditional seed starting methods.
When I first started growing my own transplants it was a struggle with those little plastic trays and 6-packs. They always felt very flimsy and my seedlings seemed to always get a bad case of transplant shock. I started searching for a new way that would be easier on my seedlings and reduced the amount of waste I was creating.
What is a Soil Block?
A soil block is a cube of lightly compressed soil and nutrients that can grow a seedling, serving as the container.
I start most of my seedlings in the micro blocker. It makes 20 ¾” blocks. For most seeds, this block will work just fine until its time to pot up the seedlings. For larger seeds like zucchini or cucumbers, I use a 2” blocker with inserts that can also be used for potting up or as I call it blocking up. Be sure to source a quality brand of soil blocker so it will last forever.
Benefits of using soil blocks:
Reduces waste and cost. Soil blocking eliminates the need for plastic pots, peat pots, or any other container, so you’ll be throwing away and spending less on year pot supplies.
Seedlings grow stronger. Roots are air-pruned once they reach the sides of the block. This means they will stop growing instead of twisting around the sides of plastic pots looking for nutrients and becoming rootbound.
Less Transplant Shock. With less disruption to the root system, the seedlings are less likely to have transplant shock when blocking up or planting out in the ground.
Easy to move. If a block doesn’t germinate you can simply remove the block from the tray and add it reclaim it in your compost bin instead of having to wait and waste space like with the plastic pots.
What you need to start using soil blocks.
Soil block maker.
I use both micro and 2-inch soil block makers. It really depends on what seed I am starting as which block is the best pick. Any small seed I start in the micro then move up into the 2-inch blocks.
For big seeds like squash, I put those directly in the 2-inch blocks.
Soil Mix For Soil Blocks.
I based my soil block recipe off of Eliot Coleman’s but I’ve done the math to break it down with the home gardener in mind.
Like any recipe, you can make substitutions for things you already have on hand or are readily available in your area.
I’ve tried several different variations of this soil blocking mix I’ve found the most important factor is the mixture must hold together well. If not you’ll find the soil blocks crumbling no matter what you do.
You’ll need to gather a few things to mix your soil block mix.
1 10 quart tote to store your soil blocking mix in.
1-quart measuring cup I use a mason jar but a paint mixing cup would work great too.
1-quart container to store your nutrient mix in
A set of measuring cups and spoons
Perlite
Sifted peat moss
Sifted compost
Now that you’ve gathered all your supplies let’s mix the nutrient mix and set it aside.
Nutrient Mix.
Rock Phosphate Powder
Blood Meal
Green Sand
Mix one part each in a quart container and set aside.
If you can’t find the ingredients in the nutrient mix you could use something like tomato-tone in its place.
Now you are ready to mix up a batch of soil block seed starting soil.
2 Quarts Perlite
3 Quarts Peat moss
2 Quarts Compost
⅓ cup nutrient mix or choice of substitute
Water
Mix all the ingredients together adding water until you reach a runny fudge-like consistency. You’re looking for the mixture to hold its shape and not be crumbly.
Once it’s all mixed up I like to use a dishpan to make my soil blocks in. Then I found cafeteria trays work best for my set up to sit the blocks on and plant my seeds. You could also make some wooden ones or buy heavy-duty plastic seed trays. I personally found the seed trays just don’t hold up well but you might have better luck than I did.
How to use the soil block maker.
Now that you have your soil block mix ready to use it’s time to get your hands dirty!
If you’re not a fan of dirt under your nails you might want to get some rubber gloves or garden gloves with the rubber coating.
I take the soil block maker and push and twist it to fill it with soil then I take my hand and make sure the block is full and level off any extra soil so they sit flat.
The most common questions I get asked about using soil blocks.
How to Water Soil Blocks
I pour water into the bottom of the tray let the blocks absorb as much of the water as they can then drain off the excess. I’ve found this method works best so you don’t wash away seeds or soil when watering from above.
Do you cover the seeds with soil?
No, you just want the seeds to make good contact with the soil. I sometimes use a toothpick or pencil to get the seeds in the indention.
You’re all ready to start your seeds using soil blocks? Let me know if you are using soil blocks and if you like them in the comments. I do love hearing how things are working in your garden.
For more gardening and homesteading posts subscribe to the newsletter and follow me on Facebook, Instagram, & Pinterest.
