Soil Blocking: Love it or Leave it?!
- Meggan Urevig
- Mar 9
- 3 min read
photo credit: ReSprout (left) Sierra Flower Farm (middle) Landon Gilfillan(right)
Every winter in northern gardens, while the snow piles up outside and the coffee pot works overtime, farmers and gardeners start dreaming about seed trays, greenhouse benches, and the promise of spring. One seed-starting method that has gained popularity in recent years is soil blocking. Some gardeners swear by it, while others quietly return to their trusty plastic trays after one messy attempt. Like most things in farming, it comes with both advantages and a few frustrations.
So what exactly is soil blocking?
Soil blocking is a seed-starting method where damp soil is compressed into small cubes using a metal blocking tool. Instead of planting seeds into plastic cell trays, seeds are placed directly into these compact soil cubes. The blocks are then set onto trays where they hold their shape while seedlings grow.
The real magic of soil blocking happens underground. As roots grow outward and reach the edge of the soil block, they encounter air and slightly drier conditions. This exposure naturally stops the root tip and encourages the plant to produce secondary branching roots. This process is called air pruning, and it leads to a dense, healthy root system with more surface area to absorb water and nutrients.
The Pros of Soil Blocking
One of the biggest benefits of soil blocking is root health. Because roots are air-pruned rather than circling inside a plastic cell, plants tend to develop stronger root systems. When it comes time to transplant, seedlings often adjust more quickly with less transplant shock.
Another major advantage is reducing plastic use. Traditional seed starting relies heavily on plastic trays and inserts, many of which crack or break after a few seasons. Soil blockers, on the other hand, are usually metal tools that can last decades. For farmers and homesteaders trying to reduce waste, this is a big win.
Soil blocking is also efficient for space. The blocks can be packed closely together on a standard 1020 tray, allowing growers to start a surprising number of seedlings in a small area. For people with limited greenhouse or grow-light space, this can be a huge benefit.
The Cons of Soil Blocking
Of course, soil blocking isn’t perfect.
For starters, the process can be messy. The soil mixture has to be very wet—almost soupy—to form blocks that hold together. Mixing, compressing, and releasing dozens of little cubes can feel more like playing in mud than gardening.
The soil mix itself also needs to be finely textured. Large chunks of bark, sticks, or coarse perlite can prevent blocks from forming properly. Many growers end up sifting their compost or potting mix before starting, which adds an extra step to the process.
Another challenge is keeping blocks moist. Because there are no plastic walls holding moisture around the roots, soil blocks can dry out faster than traditional cell trays. This means growers need to keep a close eye on watering, especially under warm grow lights.
There is an upfront cost. While soil blocking saves money in the long run, there is an initial investment. Soil blockers, trays, and mesh inserts cost more upfront than a pack of plastic cell trays.
Finally, there’s the learning curve. The first few attempts often produce crumbly blocks or uneven cubes that fall apart. But like most farm skills, practice makes perfect.
Is Soil Blocking Worth It?
For many gardeners and small-scale growers, soil blocking becomes a favorite method once they get the hang of it. The healthier roots, reduced plastic waste, and efficient use of space can make it well worth the extra effort.
But for others—especially those starting thousands of plants or working with limited time—traditional trays may still be the most practical option.
Like so many things in farming and gardening, the best approach is the one that works for your space, your schedule, and your patience level. Whether you’re pressing soil blocks on the kitchen table in February or filling trays in a warm greenhouse, the goal remains the same: strong seedlings ready to greet the spring thaw. Do you...whether you wanna test the hype or adopt it as a lifetime vibe, the more important thing is doing what is best for your family and farm-just grow your own food if you can!
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