The Best Soil Block Mix Recipes for Strong, Healthy Seedlings

December 18, 2025

A good soil mix is the foundation of successful soil blocking. The right blend will hold together firmly, retain moisture, allow airflow, and provide enough nutrients for early root growth. Without a suitable mix, soil blocks can crumble, dry out too quickly, or fail to support healthy seedlings. Below are our tried-and-trusted soil block mix recipes, including the mixes shared on the Soil Blockers website and by experienced growers.

What Makes a Good Soil Block Mix?

A successful soil block mix should:

• Hold its shape when compressed

• Retain moisture without becoming waterlogged

• Allow roots to breathe and develop freely

• Be fine enough for small seeds
  Using the right ingredients makes soil blocking easier and far more consistent, especially if you’re just getting started.

Soil Block Mix Recipes

Monty Don Soil Block Mix

This well-known mix is valued for its balance of structure, drainage and nutrition.
Ingredients:

• 1 part garden soil

• 1 part leaf mould

• 1 part garden compost

• 1 part grit or vermiculite

• 4 parts coir
  Best for: Vegetables and larger seedlings that benefit from a richer soil structure.

Lisa Ziegler’s Soil Block Mix (Flowers)

This recipe is specifically designed for flowers, producing strong, healthy seedlings that transplant easily.
Ingredients:

• 16 cups sifted peat moss or coco fibre

• 4 cups sifted compost

• 1/4 cup greensand

• 1/4 cup rock phosphate powder
  Best for: Flower seeds and slower-growing seedlings.

Using Shop-Bought Compost (Beginner Friendly)

If you’re just starting out on your gardening journey and don’t yet have access to garden compost, manure or screened bark, you can still get excellent results using a good quality multipurpose compost straight off the shelf, or use multipurpose compost as the base for any of the mixes above.

Important for Micro 20 Users

Because the Micro 20 soil blocker creates very small soil blocks, it’s important to remove any large fibrous clumps from shop-bought compost. Break the compost up by hand or lightly sieve it to achieve a fine, even texture. This helps micro soil blocks form cleanly and stay intact.

Tips for Soil Block Mixing Success

• Add water slowly, mixing as you go

• Ensure moisture is evenly distributed throughout the mix

• Test the consistency by squeezing a handful:

  • If it crumbles, add a little more water

  • The ideal soil block mix should hold form easily, and drip when squeezed in hands

Why Soil Mix Matters for Soil Blocking

Strong soil blocks encourage healthy, air-pruned roots and consistent germination. Taking time to prepare the right soil mix results in stronger seedlings, no transplant shock and easier planting out. Whether you use Monty Don’s recipe, Grandpa’s mix, Lisa Ziegler’s flower mix, or a simple multipurpose compost blend, the right soil mix helps you get the very best from your soil blocker.

Also in News