Seed Starting Series: Using Soil-block Makers Instead of Plastic Pots
Last year, we were working on ways to cut down growing costs and wanted to avoid using so many plastic pots! I recycle the ones that I have, but I wanted to find a new way to start seeds that would save me from buying more. In addition, I wanted to mix up my own seed starting mix rather than buy countless expensive bags at my local nursery. So often you can’t verify the quality of those bags and again….all that wasted plastic.
I was really excited to discover metal soil-block makers. They seemed to be a cost-effective, sustainable solution. At the same time, I was pretty skeptical. I wondered if they would erode and fall apart when watered? Would they easily become root bound? Would they be too time-intensive to make? I decided to start with one soil-block maker as a test and I’m very happy to report that none of the above proved to be the case!
We started out with the one pictured which makes (4) 2”x2” soil blocks in one go and after a few attempts I got the hang of it and it was off to the races. We decided to expand our use of soil block makers for the greenhouse this year in part because of the feature which enables you to transplant smaller soil blocks into larger ones just by pushing the smaller block into the deep impression in the larger one. It saves so much transplant time. My sense is that the plants did better than seedlings started in pots because the roots were exposed to more oxygen, they didn’t become rootbound since they naturally stopped growing at the edge of the soil block, and drainage problems aren’t an issue of course.
First, I fill a large galvanized steel tub with the seed starting mix recipe from The New Organic Grower by Elliot Coleman (See the steps below). Once I have it good and mixed, I add water. The secret is to make the mixture wet like peanut butter - definitely wetter than you would think but not runny. If it isn’t wet enough they will crumble and not properly fill the molds. If the mixture is too wet it will run and not form firm blocks. The way I figured out the right consistency was to slowly add more water and attempt to make them until I got the right consistency. One time I got cocky and overfilled the container with water - no real consequences other than I just had to wait a couple of days until it dried out. This year I plan to keep track of the amount of water I use with the mixture below so I can add the water measurement to the recipe. Don’t worry if it goes pretty slowly for the first couple of trays. Once you get the hang of it, the process really speeds up.
To make the seed starting mix, measure the peat into a large galvanized steel pail or other large container suitable for mixing soil, add the lime and mix with a large hand spade. Then add the sand, blood meal, phosphate, and greensand – mix again. Add the soil, and compost, mix again. It’s a good idea to start out with good quality peat that doesn’t have large pieces in it, you don’t want to have to screen it. This recipe makes about 2 bushels.
Once you have it thoroughly mixed and have added the water, push the soil-block maker into the soil and press it onto the side of the galvanized steel pail (or the edge of the large, strong container you are using for soil mixing). Once the soil is firmly pressed into the block maker, I top it up with a hand spade and scrape the top so it is packed in evenly - kind of like how you top up a cup measure of flour and then scrape of the top evenly with a knife. Then I gently put the soil block maker onto the tray in the location where I want the blocks to go and squeeze the spring to release. I place them in even rows til it is filled and then turn the soil-block maker sideways and place the 5th row of soil-blocks up the side then repeat. Check out my Instagram highlights for videos and please feel free to email me with any questions. For help with starting seeds indoors successfully see the upcoming blog post Seed Starting Series: Secrets to Germinating Seeds Indoors.
As always, let me know if you would like to have me come over and walk you through the steps by doing this with you for an hour or so. I learn best when someone actually shows me how - so if you are like me then shoot me an email at Christina@Modernfarmsteads.com and we will get a time set up.