Starting Seeds
In Eliot Coleman’s book “
The New Organic Grower”, he describes an intriguing process of starting seeds. Instead of the traditional plastic containers and flats, he recommends using a tool called a soil blocker. The soil blocker is filled with “blocking mix” and presses out squares with an indent for planting your seed. I was immediately on board with this method. It reduces our plastic consumption and provides a more suitable home for our seeds (less likely to dry out and no fear of root boundedness).
Unfortunately, the soil blockers can be hard to come by. They are hand-made in England and shipped over to the U.S. by only a few distributors and they can be rather pricey. They are available through Peaceful Valley (order early in the growing season as they can take a while coming from England). I also recommend buying the book, “Transplants in Soil Blocks” from PV as well.
Based on the size of our operation (we anticipate making about 20,000 starts for the spring/summer growing season), we opted for the
professional stand up floor soil blocker that can make 12 2” blocks at a time. This is the ideal size for starting most seeds. In fact we are starting all but 4 vegetables from seed (we are direct seeding carrots, parsnips, rutabaga, and radishes).
Blocking Mix Recipe (adapted from Eliot Coleman’s recipe):
30 oz.
coco fiber (we are using this instead of peat moss)
20 oz.
perlite (I’ve heard you can use rice hulls instead of perlite - something I am curious to try out)
Mix thoroughly.
10 oz garden soil (dug from our garden and sifted through a 1/2” hardware cloth)
20 oz compost
Mix thoroughly.
Add water. (The best advice I heard was that the consistency of the mix should resemble oatmeal - wet but not runny. I usually add about a 4:1 ratio of mix to water.)
A double batch of this mix fits perfectly in a 32 gallon trash can. Each batch makes approximately 250 2” soil blocks.
To make the soil blocks, I spread our mix out on a tarp in our hoop house with a 3 sided plywood tray ready and waiting. First, I make sure that the mix is wet enough by feeling it. Then I plunge the soil blocker into a large pile of mix, twisting side-to-side to fill it and rocking back and forth to ensure it doesn’t fall out. I then quickly and effortlessly lift the tool and scrape off any extra mix with either the side of the table/board or my hand. I then place the blocker directly on my tray and eject the 12 seed homes. The whole process takes about 30 seconds.
For our heat loving plants (tomatoes, peppers, and eggplants), we started them using a
3/4 inch soil blocker. I am not sure this is worth it. While more of them fit on the heat mats, they dry out too quickly. I think for our second seeding I will be sticking with 2” blocks. We will “pot them on” to 4” soil blocks once they get bigger. The 4” soil blockers come with built in inserts that press a 2” hole in the top of the block perfect for potting on.
I am really excited about how well this mix and method seems to be working for our seedlings. The germination rates are very high in our hoop house. We will be planting our first seedlings of broccoli, lettuces, cabbage, cauliflower, brussel sprouts, and beets outdoors early next week.
8 Responses to “Starting Seeds”
monica Says:
Mar 10th, 2010 at 9:58 pm
soil blocking - wow! thanks for the book tip, i’ll have to check it out. i’ve spent lots and lots of time talking &scheming more efficient seed flat logistics with the crew on the farm where i’m interning, so i’m excited to read more about the success of your transplanting efforts- i’ll be rooting for your seeds!
Darren (Green Change) Says:
Mar 15th, 2010 at 2:58 am
I’ve used a 4-block soil blocker for starting seeds in my backyard with great success. It’s a great way to plant out your seedlings without causing them any trauma.
Dwight Lockerz Says:
Mar 15th, 2010 at 6:10 pm
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Heather Says:
Mar 22nd, 2010 at 4:22 pm
Great blog!
Do you sterilize your garden soil before using it in the blocking mix?
Carmen Says:
Apr 11th, 2010 at 11:47 am
I was wondering the same thing as Heather…do you sterilize the garden soil which you put into the soil blocking mix? Also, is this the option for the soil blocking mix or do other “recipes” work just as well?
Vanessa Says:
Apr 13th, 2010 at 4:28 pm
@Heather & Carmen - I don’t sterilize the garden soil. I know it can be a cause of damping off (to not sterilize) but so far all of our plants have been really healthy. Certain batches have been weedy but I just try to find a place where I can dig a few feet down to find less weedy dirt.
Other recipes can work well. Eliot Coleman mentions growers that use just compost with soil blocks. I made lots of substitutions from Coleman’s basic mix. For example, instead of using vegetable compost (we didn’t have access to any), I used less of the fertilizer mix with a horse manure based compost. Coleman lists alternatives to blood meal that would allow you to make a vegan blocking mix. I think it is mostly about using what you have access to and are comfortable with.
vegetable rack Says:
Aug 24th, 2010 at 9:28 am
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