Soil Blockers

The Johnny's Selected Seeds soil blocker

Here’s Herbdoc with something that should make seed starting easier:

I finally decided to invest in a soil blocker instead of purchasing peat pots and saving various containers for seed starting every year.  These small tools turn out blocks of growing media that have been compressed into their own containers.

Seedlings grow very strong root systems in these blocks and cannot become root bound as they do in regular pots.  In order to hold its shape and retain moisture, the mix which is used to fashion the blocks needs some fibrous material.  Although commercial mixes can be used, some contain wetting agents or fertilizer making them unsuitable for organic growing methods.

Eliot Coleman in the New Organic Grower recommends the following recipe for about 2 bushels of mix:

3 (10 qt) buckets of brown peat

½ cup lime

2 (10 qt) buckets of coarse sand or perlite

3 cups equal parts of blood meal, colloidal phosphate and garden sand

1 (10 qt) bucket garden soil

2 (10 qt) buckets of well decomposed compost

Moisten the mix using one part warm water to every three parts of blocking mix.  The mix should have the consistency of peanut butter or wet cement.

Water should ooze through the blocker as the blocks are made.

I found gathering all of these materials tedious so when I purchased my blocker from Johnny’s Seeds ($29.95), I also ordered a bag of organic 512 mix which is available in 20 or 60 qt. bags.

The blocker itself is easy to use!  Just make a pile of mix about 1 ½ times deeper that the height of the blocker.  Plunge the blocker down into the mix, giving it a quarter turn, lift, and set the blocker in your tray.  Push down on the handle and raise the blocker.  Presto!  Four neat little pots.  Rinse the blocker in warm water before making the next set.

The blocker even makes its own indentations for the seeds.  Cover with additional soil (or not) as specified on the seed packet.

I’m really excited to have this new tool and not to have to purchase peat pots any longer.  The peat pots easily fell apart or were too dry or too wet, and I had to rip the tops off every pot when transplanting so they wouldn’t wick water.  Seedlings grown in the soil blocks are said to establish themselves more quickly because they have stronger roots which are less disrupted when transplanted.

Let us know if you’ve used the blockers and what your results have been.


About dirtynailz

Writer for a daily newspaper, gardener, tree hugger, orchid-grower, photographer, animal lover, hiker, wilderness seeker. Proponent of clover in the lawn and a dog on the bed.
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2 Responses to Soil Blockers

  1. Wendy says:

    I’ve been coveting this for years. In the end, I wonder if it would be worth it for a small backyard gardener to own one? Would it be worth the money, and more imporantly, time to set up and crank some out if I only need a few?


  2. HerbDoc says:

    I can’t answer that because I’m so new to it, but the initial investment
    of $29.95 isn’t too bad, and you can use your own compost or growing medium if you wish. You’ll be making 4 “pots” at a time so filling a tray goes pretty quickly, and Johnny’s also has another model that punches out 20 mini blocks, but I think you’d be looking at transplanting then. Actually I just looked at Johnny’s site and both the single blocker and the mini one are out of stock so if you’re interested I’d say hurry! As I said in the blog, just not having to buy peat pots every year or store cottage cheese containers was enough for me to spring for one!


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