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How I Learned to Hate Soil Blockers and Regret their Purchase

April 23, 2012

Maybe that title is a tad dramatic, but I really do regret going with soil blockers. I’d read so many good things about them in Eliot Coleman’s books, and I could never figure out why other farmers/gardeners I knew didn’t use them (maybe I should have asked). I suppose I should preface what is to come with a big caveat: a lot of the problems I’ve been having could easily be the result of user error and other issues with our seed starting operation. At the same time though, I based my use of the soil blockers off the best information I could find.

Pros of the soil blockers:

Micro 20s

(1) The main benefit (that I’ve found) is that you can fit a lot more starts into a small area. This is a picture I  took of my tomatoes and peppers. Each one of these flats holds around 300 micro-20 soil blocks, compared to 40 or so with the standard seed starting trays (you can kind of see these up in the right hand corner). So, if you have limited space on a heating mat and need to start a lot of seeds, these are great. That is all for the pros.

Cons of the soil blockers:


(1) More work for me: This is a picture of 20 soil blockers (the next step up from the micro-20s) and 20 standard seed starting cell flats. I would normally starts all my seeds in the standard cells, and except for tomatoes and peppers everything would stay in these flats until I transplanted them. With the soil blockers, the micro-20s are just used for germination, and then the starts are transplanted up into the next size blocker (extra work). You can also start everything in the larger size block (no transplant), but as you can see from this picture the soil blocks take up more room than the standard cells.

(2) Poor block shaping: The point of soil blockers is that you can compress a soil mix into a block that will hold together and provide a hole for the seed or smaller soil block to go into. Try as I might, I could never get well formed soil blocks, especially with the micro 20s. Most of my micro 20s lacked any sort of divet, which made it impossible to cover the seeds in any way or keep them on the block. When I made the larger blocks, my micro 20s wouldn’t fit into their holes – I managed to destroy a lot of the blocks the first time through, and finally ended up pulling the bottom off the micro-20s. It was also impossible to really squish the micro-20 into the larger block.

(3) Poor germination: This is the one issue that I think is the most likely caused by my errors (greenhouse too cold at night, not enough or too much water), but I have never had this many problems starting seeds. I have restarted my tomatoes and peppers twice, and my onions  and cabbage three times. I gave up on leeks when none of them germinated, and even my best performing crops (broccoli, kale, and chard) only showed 50 % germination. A lot of seeds never germinated at all, and then many of them died shortly after germinating although it is hard to tell why.

So, I have about half as many plants as expected, and they are less than a 1/3 of the size I expect. Next year I’ll probably switch back to cells and try to keep the hoophouse warmer at night.

On a positive note, we had a beautiful weekend and the garden is really shaping up. I’m getting compost delivered on Thursday, and I’m hoping to start sowing crops over the weekend even before we get the deer fence up. I figure deer can’t or won’t eat seeds, so I’ll have a week or two before we have to have a fence up.


5 Comments leave one →
  1. Rita permalink
    April 23, 2012 10:25 am

    What about a newsprint origami-ish “box” which could be planted in toto when the seedling is large enough. It’s not much different from the flat starts but you wouldn’t have to pull out the seedling and disrupt the roots.

    • April 23, 2012 10:33 am

      Interesting idea! Unfortunately, it would take a HUGE amount of time to fold all the boxes we would need, and it would have to be done every year. In my experience, pulling the plants out of the cell flats doesn’t disturb their roots. The reason soil blockers are supposed to be better for plants is because the roots are air pruned instead of getting root bound – the air stops the roots but they are ready to grow when given more soil. Since I don’t keep my plants in their containers for more than a few weeks, or I transplant up, root bound hasn’t been a problem in the past.

      • Rita permalink
        April 23, 2012 11:09 am

        Isn’t there some sort of dibble wrapper thingie to make the pots quickly?
        Sounds like pots might be the way to go.

  2. John Brown permalink
    April 24, 2012 9:14 pm

    We have been saving toilet paper rolls, cutting them in half and planting in them then puting them out tube and all. They work really well. Roots grow right through the paper. Not sure what is in the stuff tho. I’m sure you have lots of friends who would happily save rolls for you over winter.

  3. anon permalink
    April 12, 2013 10:38 am

    “have never had this many problems starting seeds”. My thoughts exactly. 90% failure rate.

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