Soil Block Recipe for Your Soil Blocker – Mother Earth News


Thinking about using your own soil block mix and soil blocker to start your own seeds this spring? Try this soil block recipe for quick germination.

As I dig deeper into hobby gardening, I’ve experimented with starting seeds in late winter to jumpstart the growing season. This practice saves money, and I find it immensely satisfying to watch seedlings emerge under a grow light indoors, especially when I’m still hibernating from frozen temperatures. Once you have your grow system in place, there’s a huge cost savings in buying seeds and soil compared with buying greenhouse plants to transplant. Even better, it can become an endless cycle if you practice seed saving at harvest time.

Multiple books in the Mother Earth News Store teach seed-saving. Simply click on the “Gardening” tab and select “Seeds & Seed Starting.” I recommend Beginning Seed Saving for the Home Gardener by Jim Ulager. The author covers a variety of seed-saving topics, including principles of vegetative and sexual reproduction, easy inbreeding plants, more challenging plants, and why seed-saving belongs in the home garden. I recommend reading up on the topic and freeing yourself from the commercial seed industry. In no time, you can have an extensive seed bank with all your favorites.

Seed Starting with a Soil Block Mix

I’ve never cared for plastic containers (often non-recyclable) for seed-starting. These flimsy, tiny pots rarely last more than a growing season and take up a good deal of storage space. In the past, I’ve created origami newspaper boxes to eliminate plastic cell trays. This is a time-consuming process, and seedlings became root-bound. When you use any container to start seeds, the roots encircle the barrier. Root-bound plants take longer to acclimate when transplanted outdoors and often experience shock when being hardened off.

Doing away with containers avoids root-bound seedlings. Various cultures have employed the soil-blocking method for centuries. It eliminates the need for untangling seedling roots upon transfer. Transplantation often causes damage to seedling roots, thus affecting the plant’s success. With soil blocks, roots “air prune “themselves at the blocks’ surface and extend into new surroundings once rehomed, up to three days sooner than container seedlings.

After experimenting with the Soil Blocker set, I’ll never go back to storing stacks of cracking, non-recyclable containers. These eco-friendly and durable tools are simple enough for beginner gardeners and produce single blocks of molded soil to jumpstart your garden with less waste. Additionally, the seedlings will be heartier with high germination rates.

Soil Blockers are ideal for nurseries and domestic use. The Soil Blocker set includes everything you’ll need to make your own soil blocks. You’ll receive the Mini 4 Soil Blocker, the Micro 20 Soil Blocker, and the Cubic Inserts for the Mini 4 Soil Blocker. These items can all be purchased individually on the Mother Earth News Store site as well.

The Micro 20 Soil Blocker produces dense 3/4-inch cubes of moist, nutrient-rich soil. Less mass means you’ll need less space during germination, and you’ll make the best use of limited heat mat space. This size is ideal for crops that thrive with extra heat, such as tomatoes, celery, eggplant, peppers, tomatillos, and ground cherries. Smaller, slower-to-germinate seeds, such as oregano, thyme, parsley, basil, lavender, and hyssop, also start well in the micro cubes and germinate in a fraction of the time. Once the plant emerges from the 3/4-inch blocks, transplant to 2-inch blocks made using the Mini 4. The Cubic Insert makes the perfect indentation for 3/4-inch blocks to nest into 2-inch blocks. The 2-inch soil cubes are great for starting larger seeds with less germination time, such as zinnias and lettuce.

Soil Block Recipe

In addition to the Soil Blocker set, you’ll need a tub filled with a special seed-starting mix, bottom trays to place blocks, organic seeds suited to your region, and a container of water to rinse your tools in between uses. To maintain the soil blocks’ integrity and shape, the best soil block mix should consist of half peat moss or coconut coir. The fibrous consistency binds materials and helps retain moisture. The Mother Earth News Store listing for Soil Blockers has a complete demonstration video and a soil block recipe for seed-starting success.

Top view of bean seeds in soil blocks.  Compressed soil blocks ar

In a sizable tub, mix 8 cups sifted coconut coir or peat moss, 2 cups sifted compost, 1/4 cup fine vermiculite, and 1/8 cup green sand. Variations of soil block mediums include garden soil, coarse sand, perlite, lime, blood meal, colloidal phosphate, and compost. Research soil block recipes and decide what works best for you based on what you already have on hand. Once you combine the dry mixture, you may want to sift it again to remove large chunks and debris that will keep your blocks from forming. Separate enough for your current seed needs and combine the dry mix with warm water using a ratio of 3-to-1. It shouldn’t be excessively runny or dry, but should be wetter than soil used for cell trays, with a consistency similar to chocolate fudge or concrete mix. With experience, you’ll become familiar with how to create an excellent soil balance. Keep some dry soil block mix nearby in case you over-moisten.

To create the soil blocks, press your tool into the wetted mix and twist as necessary to fill the form. The resulting cube should be dense and free of air pockets, so hand-pack as necessary. It’s possible to overpack the form, making it difficult to release the blocks. Once filled, scrape the edge of the Soil Blocker to create a smooth, flat base. Release the cubes by pressing the spring-loaded handle over your planting trays. If crumbling occurs, adjust the consistency of your mix or pack the form more firmly and try again until you’re happy with your results. The best blocks will be solid with sharp edges.

Sow seeds as you would normally, using one or two per block and pushing them to twice their depth. The blocks shouldn’t require watering for the first few days. After the top millimeter appears dry, you’ll need to use bottom-watering or a mister or spray bottle to moisten. A heavy water stream will erode the shape of the blocks.

As with any new endeavor, I recommend journaling your observations and notes on this process to adjust future attempts. Experiment and jot down that perfect balance of soil for your soil block mix next season. Keep track of germination times to accurately plan seed-starting the next year.

Using soil blocks and seed-saving can take your garden to the next level of sustainability and independence from commercial growers. You can be more selective with your organic seed variety and know the origin. Higher-volume, nutrient-rich soil blocks will produce more vigorous seedlings with minimal root disturbance during transplantation. Plants will quickly resume growth and experience less shock after being planted in your garden. Even better, you’ll waste less lessons by eliminating plastic cell trays and tiny pots. Soil blocks produce healthier, quicker transplants without being constricted by containers. Each plant will have access to more nutrients and oxygen per volume and will develop a stronger root system with an increased surface area.

I’ve found that the time it takes to create soil blocks is comparable to loading individual plastic cell trays for planting. Upon transplanting, there’s no trash to collect and there are no roots to pinch. Home-grown seedlings seem to outperform store-bought plants that often have to recover from shock after being relocated to the garden. Ditch the plastic and start seed-saving and soil-blocking to produce superior seedlings with little extra effort.


Christine Stoner is an editor for Gas Engine Magazine and works on various other titles within Ogden Publications. She has a passion for fitness, healthy living, and sustainability.

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