After much anticipation, I finally got to break out my new soil block maker over the weekend. It was a lot of fun---kind of like making mud pies, except with the added bonus of knowing that I’ll have plenty of baby heliotrope, daylilies, and lobelia in a few weeks. Making soil blocks takes a bit of practice, but if you keep a few things in mind, you’ll be a soil block pro in no time

Soil for Making Soil Blocks
This was the issue that originally drove me nuts regarding soil blocks. I received a soil recipe along with my block maker, and if you search online, you’ll find plenty of recipes for homemade soil for your block maker. In fact, Eliot Coleman (who is wholly responsible for my obsession with soil blocks) has a fairly complex soil recipe in his excellent “The New Organic Grower.” If you’re into making up your own custom potting mixes, you’ll love this part. I’d rather just get planting. While searching online, I came across a thread on GardenWeb about soil block making. What caught my interest was that several of the professional growers on the forum said they just use the commercially available, sterilized seed starting medium that we normally see in the garden centers at this time of year. Since I have plenty of that on hand, I used it, and it made perfect, sturdy blocks.

Prep for Block Making
The easiest way to make the blocks is to get a large tray or bin to work in. I used a large plastic potting tray, and it worked great. The reason you need a fairly large area is because you’ll be mixing in lots of water, and because you’ll need room to maneuver your block maker while actually making the soil blocks. I found that it was a good idea to put your flat or whatever you want to use to ultimately hold the soil blocks right next to your mixing area so you can make the blocks and dump them right onto their ultimate resting place. Put a large amount of soil into your mixing tray or bin (more than you think you’ll need----the soil gets compressed quite a lot in block making) and pour warm water onto your dry soil. You want your soil to be thoroughly moist. When you pick up a handful and squeeze, a trickle of water should drip out of the soil. This will help you form nice, solid blocks, and assure that there are no dry pockets in your soil. It’s also a good idea to have a small tray or bucket of clean water nearby to dip your block maker into between batches.

Making the Blocks
To make the blocks, pile your soil up so it’s about twice the depth of your block maker. Press your block maker into the pile of wet soil, giving it a slight twist to seat the soil in the maker. Once the block maker is full of soil, move it over to your flat (holding it at a slight upward angle to keep your blocks from falling out prematurely) and then place the block maker where you want your blocks to be. Eject the blocks by slowly pulling up on the handle of your block maker. Be patient! Some blocks may stick a bit---let them fall out in their own time. Once you’ve got them all out, you’ll need to slide the blocks apart a bit---you want about 1/8” of space between the blocks so the roots of one block don’t start growing into other blocks. Repeat until you’ve made all the blocks you need.

Planting the Blocks
Most block makers make a handy depression in each block for sowing your seeds or placing cuttings. If yours doesn’t, you can make a small hole with a pencil or dibble. To cover the seed,simply sprinkle some soil or vermiculite over the top of the blocks.

Caring for Soil Blocks
Soil blocks start out perfectly moist, which is why germination is so easy with them. The key is to keep them moist. Letting the soil dry out is bad for the seedlings, of course, but it also makes it difficult to get the block evenly moist again. A strong spray of water will erode the blocks, so the best way to water is to mist the blocks regularly with a mister. Watch the blocks at the edges of the flats---they will dry out faster than the ones in the center.

Growing in soil blocks requires learning a few new techniques, but part of the fun of gardening is that we get to learn so much along the way. I also like that there is no added cost or waste when growing with blocks----I don’t have to buy little plastic cell packs, or feel guilty when I have to finally toss them after a couple years of reusing them. And, if Eliot Coleman is to be trusted (and I am inclined to trust him), they will result in stronger, healthier seedings as well. According to Coleman:

“Instead of the roots circling as they do upon reaching the wall of a container, they fill the block to the edges and wait. The air spaces between the blocks and the slight wall glazing caused by the block form keep the roots from growing from one block to another. The edge roots remain poised for rapid outward growth. When transplanted to the field, the seedling quickly becomes established.”

For More About Soil Blocks:

Make Your Own Block Maker
Block Makers from Johnny’s Selected Seeds
Marc @ Garden Desk's post about his block maker