A few years ago I was reading Eliot Coleman's book The New Organic Grower and was intrigued by his discussion of soil blockers. I always seemed to have the worst time keeping enough cell packs on hand for starting my seeds and was never thoroughly happy with them. Soil blocks seemed like the sustainable solution to this problem. Not only would I not have tons of those stupid little broken plastic 6-packs after their use, but the soil blocks provided another benefit--healthier roots. The roots will fill the block, but when reaching the edge (air) will stop and wait to be potted on, unlike in the plugs or pots where the roots will wind themselves around and become a matted rootbound mess. Also, the roots are not disturbed hardly at all when potting on since you just pick up the block and set it in the next sized block or in your pot. So, I ordered my two soil blockers from Fedco/Organic Growers Supply. The all-metal one creates 4 2-inch blocks, while the micro-blocker makes 20 little blocks in a 3"x4" area. The metal blocker has inserts that will make micro-block-sized indents for potting on the micro-blocks.
The nifty blue cushion did not come with the micro-blocker. It is the invention of my friend who got sick of getting scraped-up knuckles when she used it. It works wonderfully!
So you start with potting soil or starting mix that is wet enough to clump together. I prefer Vermont Compost's Fort Vee potting soil. I have also used Eliot Coleman's potting soil recipe, with great results, but it can be a hassle to get all the ingredients and mix them well enough. I did consider borrowing my dad's cement mixer for mixing... that would've worked!
You press the blocker into the wet soil firmly to fill the blocks. I have found that I need to press the soil into the micro-blocker's holes with my fingers to evenly fill it or the outside ones aren't packed well enough.
Then you pop the blocks out into a tray. You pull up on the handle and the spring-action ejects the blocks. This part can be a little tricky, but after a couple tries you get the hang of it! Each block has a little indent in it to hold the seeds. Obviously since the blocks are verrrry little, they work best with small seeds. I use them for my tomatoes and peppers, since I put them on a warming mat and the mini-blocks are easy to keep warm and speed germination. I also use them for a lot of small-seeded herbs and lettuce.
Here is a full tray of micro-blocks all seeded. The larger seeds are peppers and the small ones are tomatoes. As you can see, a tray holds a LOT of micro-blocks. Soon after the seeds germinate, they run out of space in their micro-block and need to be potted on to the 2-in blocks. The advantage here, though, is that I can get a lot of seeds started with only using 3 warming mats. After they have germinated, most plants are content at room temperature or slightly warmer, so don't really need the warming mat.
After seeding, I mist the top of the blocks and use a clear dome to keep in the moisture. I check daily and mist if the blocks seem to be drying out.
In the picture above, you can see the seedlings starting to put out roots, just 2 days after planting! And interestingly enough, I learned from The New Organic Grower that not all seeds need to be covered to germinate. Onion family seeds do prefer the dark for germination. So they should be covered with dirt or, if not coverering them, started in a dark room.
Ta-DA!! Little tomato plants just 5 days after planting. (I love time-stamps on pictures!!) These will need to be moved to 2-in blocks soon. The peppers you can see are starting... they are a bit slower germinators.
This is what the 2-inch blocks look like. I can fit 50 in a tray. These have the regular seed indent in them (not the square for potting on micro-blocks). I use them for onions, scallions (in bunches--just put 12 seeds in each block and they are pre-bunched!), and any larger seeds--cukes, watermelon, broccoli, cabbage, nasturtiums, okra, etc. These blocks are quite a bit easier to make than the micro-blocks. There is a 20-count blocker for these size blocks that I think would be a blast to have, but the price-tag is a bit too much for this frugal gardener. There is also a single 4 inch blocker available, but again, the price tag is a bit much and I have lots of 4-6 in pots, so I use those.
I don't use the soil blocks for all my plants. This year I am starting my leeks in 2X3 inch rectanglar trays. A friend who grows perennials for market had gotten a bunch of the trays and decided they didn't work for what she wanted, so she passed them on to me. I had not considered growing leeks in bunches until I saw them sold that way at a local nursery. They grow together, then you simply separate them when planting in the garden. I am planting some onions in the same manner, but most of my onions I grow in groups of 4 in the soil blocks. This was another idea from Coleman's book, and it has worked very well for me. I also use cell-packs (I reuse everything I can--so I have quite a few from nursery flowers) for some things, mostly marigolds and other flower starts.
Here is my current setup for my early starts. I can fit 8 trays on here (and after a planting spree today, it is full). When I start potting on the tomatoes, I will have to expand to another table with a light system set up over that. I'm hoping that the snow will go away and by mid-April I can start using the cold-frame (though that will have to be with a backup heater and insulated cover for cold nights). By that time, the plants are starting to take over the house, and every spare table area is covered in greenery!
I really enjoy this early chance to play in the dirt. I even get to make mud!!! Wheee!