Master Gardeners are part of a network of not-for-profit associations throughout North America. Members share a common interest – a passion for gardening and a willingness to share (at no cost) environmentally responsible gardening knowledge within their communities. Operating under the umbrella of the British Columbia Master Gardeners, the Thompson Shuswap Master Gardeners chapter was established in 2010 and its members have volunteered 10,000 plus hours throughout the Thompson-Shuswap region.

Who would have known that what I learned about making Jello molds could come in handy in the garden? That’s the idea behind soil blocking — a technique gaining popularity with gardeners looking to start seeds sustainably.

Much like popping Jello from a mold, soil blocking involves pressing damp soil into a mold that forms uniform blocks. Seeds are sown directly into these cubes, eliminating the need for plastic trays or pots.

I first discovered soil blocking while trying to cut down my nursery purchase costs, reduce microplastics, and improve my seed-starting process. Although the method has ancient roots, it was adopted by the Dutch and popularized in North America by organic farmer Eliot Coleman.

One of the advantages of soil blocking is its environmental impact. Traditional seed trays are often made from single-use plastic, which can crack or degrade after a season. Even a sturdy 72-cell plastic tray can cost around $20 and last only a few years. Soil blocking, on the other hand, uses long-lasting tools and can significantly reduce plastic waste.

For this project, I tested several soil blocking tools and experimented with gathering ingredients for several DIY soil block recipes. I then trialed each combination under real-world conditions. My goal was to find the most effective tool and soil mix combinations for producing healthy seedlings.

I started with a soil blocker, seed-starting ingredients, trays to hold the blocks, and a commitment to daily watering. The Swift Blocker Canada tool is user-friendly and will last a lifetime, but it is also one of the more expensive options, starting at $112. Lee Valley and Johnny’s offer alternatives in various sizes and price points, ranging from around $35 to over $200. That said, the startup costs for soil blocking can be high. The technique comes with a learning curve.

Soil mix matters a lot. If the mix isn’t right, your blocks can crumble or dry out. The ideal mix holds moisture, binds well, and allows airflow. Gardener’s World offers a serviceable recipe. A pre-made option is Johnny’s 512 mix, and a peat-free option is a recipe of four parts FoxFarm Bush Doctor Coco Loco potting mix and one-half part wool pellets. This held moisture well and supported strong root development.

Although soil blocking requires upfront effort and investment, it can be worth it for long-term gardeners. It’s highly space-efficient; for example, I was able to grow over 200 seedlings on just three small steps on my porch. This method can also extend the growing season since you can start seeds in covered areas. It may save money over time, reducing my purchases of 4” nursery plants. Soil blocking can also support plant health by promoting natural root pruning and minimizing transplant shock.

While it may not suit the casual houseplant grower, soil blocking can be rewarding for those who enjoy garden tinkering and experimentation. Although the ecological health benefits of reducing plastics are evident, I would understand why some gardeners would find another way to support the environment; it’s for serious gardeners.

Submitted by Sumer Seiki