With frigid temperatures outdoors, I’m sure many of you can relate to the growing desire to do something garden-related, well before Mother Nature says it’s OK to safely plant outside. For me, it’s all about starting seeds indoors. By mid-February, seeds are sown and I’m checking daily for the first signs of germination. Over the many years that I’ve been starting seeds under lights, I still look forward to the process and love tending to my many seedlings for the eight weeks or so I’m able to nurture them until transplanting outdoors.
For the most part, the steps in the seed starting process don’t change much from year to year. But to mix things up, I’m always trying new and different variables. One of the new discoveries for me occurred a few years ago when looking for alternatives to the ubiquitous plastic seed trays. I’ve used just about everything, from recycled and reused pots, yogurt containers, butter tubs, milk cartons, food containers, even pizza boxes. Almost anything goes as long as it’s able to contain the soil and allows water to drain.
My ah-ha moment came when I learned about a method of starting seeds without containers. The term most often associated with this method is soil blocks. Hard core gardeners and farmers have been using them for years and they’re catching on across the country with adventurous home gardeners too. Also known as “potting blocks,” they’re made from lightly compressed cubes of soil. The blocks not only serve as the growing medium for seedlings, but also as the container. The blocks are pressed by a form and molded into a cube. While you might think that a block of soil sounds fragile, it isn’t. With the proper moisture, combined with a fibrous growing medium, the soil block will easily hold together. The bigger the roots get, the sturdier the block.
Another nice advantage of using soil blocks is that the roots do not encircle the block as they grow. Instead, they stay within the growing medium because of the air spaces between the blocks. If you’ve ever head the term “air pruning” this is an example of that. The beauty of roots growing in this fashion is that when the blocks are transplanted into the garden, the seedlings establish quickly into the surrounding soil, with little risk of transplant shock. Even plants such as cabbage, sweet corn, beets and cucumbers that don’t like their roots disturbed can be grown successfully with soil blocks. Normally these types of plants are not recommended for transplanting since their roots are particularly susceptible to transplant shock.
The tool for making these seeded cubes is known as a soil block maker or “blocker.” They come in a variety of sizes. A popular option for the home gardener has four two-inch square compartments. The process to create soil blocks is simple, and fun. First, you need to wet the soilless seed starting mix in a big tray and mix it together with your hands into a thick slurry, about the consistency of oatmeal. Then fill each compartment of the blocker with the growing medium. You use it like a cookie cutter to make the blocks of soil to plant your seeds into. Just push the block maker down, turn, squeeze and lift. Then, set the filled blocker into a tray and release. You can then plant the seeds directly in the depressions created.
The key to success is starting out with the proper soil mix and moisture content. An industry standard is Eliot Coleman’s mix that he describes in detail in his book, “The New Organic Grower.” Bagged, ready to use seed starting mix works well too. Just add water.
If you’re tired of washing out plastic pots each year, or bothered by the thought of throwing out plastic containers, or just looking for a new venture to break the old routine, then soil blocks could be just the ticket for you. You can find more information at www.pottingblocks.com , www.johnnyseeds.com and other websites. You can even watch me in action making soil blocks in our episode on seed starting at www.GrowingAGreenerWorld.com/episode-402-seed-starting-101 for an excellent demonstration.