The Benefits of Using Soil Blocking for Seed Starting

Starting seeds indoors can be a tricky task. Many gardeners struggle with issues like root disturbance, damping-off disease, and transplant shock. Soil blocking offers a practical solution to these common problems. This method has gained popularity among gardeners who want healthier seedlings and a more sustainable approach to seed starting.

Soil blocks with seedlings growing, soil block seed starting method

What Is Soil Blocking?

Soil blocking is a technique where soil is compressed into small, solid blocks that serve as individual seed-starting units. Instead of using traditional plastic pots or trays, gardeners use a soil blocker tool to form these blocks. Each block holds a seed or two and provides a compact, nutrient-rich environment for seedlings to grow.

This method eliminates the need for plastic containers, reducing waste and promoting better root development. The blocks are usually made from a mix of soil, compost, and other organic materials that retain moisture while allowing air to reach the roots.

Why Soil Blocking Works Better for Seedlings

One of the biggest challenges with seed starting is transplant shock. When seedlings grow in pots, their roots often circle around the container, becoming root-bound. This can stunt growth and make transplanting stressful for the plant. Soil blocks encourage roots to grow outward naturally, air pruning them when they reach the edge of the block. This results in stronger, healthier root systems.

Another advantage is reduced risk of damping-off disease, a fungal problem that kills seedlings. Soil blocks dry out faster on the surface than traditional pots, which discourages fungal growth. The blocks also improve airflow around the seedlings, further lowering disease risk.

How Soil Blocking Saves Time and Space

Using soil blocks can save space in your seed-starting area. Because the blocks fit tightly together without containers, you can fit more seedlings in the same space. This is especially useful for gardeners with limited indoor space or those starting many varieties at once.

Soil blocking also cuts down on watering time. The blocks hold moisture efficiently, so seedlings need less frequent watering. Plus, there’s no need to clean or store plastic pots after use, which simplifies cleanup.

Environmental Benefits of Soil Blocking

Plastic waste from seed trays and pots is a major concern for many gardeners. Soil blocking eliminates the need for single-use plastic containers, making it an eco-friendly choice. The blocks are fully biodegradable and can be planted directly into the garden soil, reducing transplant shock and waste.

By using organic soil mixes, gardeners can avoid synthetic fertilizers and chemicals. This supports healthier soil ecosystems and promotes sustainable gardening practices.

Getting Started with Soil Blocking

To try soil blocking, you’ll need a soil blocker tool, which comes in various sizes depending on the type of seedlings you want to grow. I purchased my soil blocks from Johnny's Selected Seeds and I use the 4 and 5 block soil blockers almost exclusively. A fine, well-draining soil mix is essential. Many gardeners use a blend of compost, peat moss or coconut coir, and perlite or vermiculite (I'll share my recipe in another post).

Statice seedlings in soil blocks

Here’s a simple step-by-step guide:

• Moisten your soil mix until it holds together but is not soggy.

• Fill the soil blocker with the mix and press firmly to form a solid block.

• Release the block onto a tray or flat surface.

• Plant one or two seeds in the indentation on top of each block.

• Keep the blocks moist and provide warmth and light for germination.

  
  

Once seedlings develop their first true leaves, you can transplant the entire block into the garden or a larger container.

Practical Tips for Success

• Use a seed-starting heat mat to maintain consistent warmth, which helps seeds germinate faster.

• Avoid overwatering; soil blocks should be moist but not waterlogged.

• Label your blocks clearly, especially if you’re growing multiple varieties.

• Start with easy-to-grow seeds like lettuce, herbs, or brassicas to get comfortable with the technique.

• If you don’t have a soil blocker tool, you can try making small soil cakes by hand as a beginner experiment.

  
  

Why More Gardeners Are Choosing Soil Blocking

Gardeners who switch to soil blocking often report stronger seedlings, less waste, and a more enjoyable seed-starting experience. The method fits well with organic and sustainable gardening goals. It also encourages a closer connection to the growing process, as you work directly with soil and seeds without plastic barriers.

Whether you have a small balcony garden or a large vegetable patch, soil blocking can improve your seed-starting success and reduce your environmental footprint.