Germination Frustration with Soil Blocks

12 years ago

For the first time this year I have been trying to use soil blocks to germinate seed. I'm using 2 inch blocks.

I first tried using the starting mix recipe given by Eliot Coleman, a peat/phosphate/greensand/compost mix. I actually did get about a 5% germination rate for head lettuces. Given such poor results, I switched to using a (reduced) peat/compost/potting soil mix (both mixes also contain pearlite). This second recipe, minus the peat, gives me about 100% germination when used in cells or pots. Alas, the seed in the blocks refuses to sprout.

I've tried using lights indoors and growing outdoors, with the same results.

Have any of you had this problem and found a way to solve it?

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Comments (6)

digdirt2
12 years ago
I've had the same experiences with them and to be honest, have seldom read about much success using them with the exception of Coleman. The soil mix seems to be far too vital an element for me - shouldn't need to be that precise. Plus watering them correctly without way over-watering is difficult IMO. Not to mention the cost of the initial investment in the equipment.

But I will say that IME a good part of your germination issues are because you are using the 2" blocks rather than the smaller ones. It is the equivalent of trying to germinate seeds in 6" pots instead of in 1" cell packs - results are never as good. It is simply too much soil and water volume for good germination and the seed usually rots or even if it germinates the seedling dies off quickly.

How to solve it? Sorry to say tat other than using smaller blocks I never found any solution and finally just gave up on them (as have many others) and went back to more standard methods. 10x better results.

Dave
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biblion
Original Author
11 years ago
Thanks, Dave. Wish I'd had the benefit of your experience before I bought the blocking tool.
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Elliott Coleman is the king of the soil block. The New Organic Grower is a great reference. I have always used his soil block recipe, which is 30 units brown peat , 1/8 unit lime, 20 units coarse sand or perlite, 3/4 unit fertilizer (equal parts blood meal, colloidal phosphate and greensand), 10 units soil, 20 units compost. Just noted as I copied this out that he suggests a germination mix of 16 parts peat, 1/4 part colloidal phosphate, 1/4 part greensand, 4 parts compost. I have never used this one. I used to start tomatoes, peppers and onions in 2" blocks with the first recipe. One thing that works really well is 4 onion seeds in one 2" block, then plant it out that way. Now I often do bulk seeding of lots of different kinds of flowers, and don't find soil blocks as useful - take up more space.
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Upon reflection, regarding watering, I am sure it is saving me time but it might have more to do with the fact that everything is the same medium and consistency rather than strictly because they are soil blocks per say. I agree that it would make more sense that evaporation would be less due to plastic sides but perhaps because the blocks are so close together, it isn't making that much of a difference. I'm seed starting for my yard, my, mom's yard, and my aunt's yard (with a very limited budget) so I've been reusing any square or round pots I can get my hands on over the years. Historically, my trays of seed starts are not overly consistent in size or medium and that might have more to do with the faster, easier watering with soil blocks. If I had same size, same shape, same growing medium, that might make it the same speed as soil blocks. I just haven't had that experience to know for sure. On a side note, I really enjoy watering the soil blocks. It is more entertaining to be sure. :) Regarding what happens to the root pruning on the sides, I am thinking that they start growing again later when they meet soil after being transplanted. I am getting this idea based off of what the 3/4" block plants do when I stick them in the slots of the 2" blocks. I took one apart to check it out and there weren't any "stubs" that ended where the roots had stopped before transplanting. There were, however, many roots that went straight to the 2" block. This was after a few days (with my faster growing plants). Honestly, I am ridiculously focused on making sure I'm not killing any spiders when I bleach my pots so it takes me longer than it otherwise would. That is probably another reason this seems so much better to me. My peas, spinach, lettuce, and beets transplanted like a dream. I usually have at least some drooping, etc. Dave- I think you're right about some veggies being better than others. I don't think I'm going to use them for onions again. It worked way better in the old strawberry container I reused from the kitchen. Carrots are so far also not the best which is annoying because I would love an easy way to get them started earlier. Peanuts, on the other hand, are starting way better than I thought they would. I started them in 2" blocks but I think I'll have to transfer them to 4" pretty quickly.
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I purchased a soil block maker a year or two ago and just love it. I use my own mix and don't follow any sort of expensive recipe - just make something that holds together with peat, compost, planter mix etc. The secret is getting the water content right. Making the blocks themselves takes some practice, but don't most new techniques? Making them can be a lot of fun. I put my soil blocks in various water-holding containers/pans/trays and try to leave one corner without a block for more safely adding water. If you water from above, the blocks will disintegrate, so it's better to allow a slow stream of water to partially fill the side or corner of the container your blocks are in, and they saturate from the bottom. Air pruning allows the roots in your blocks to not get root bound as they often do in containers, but the roots grow very well. And the blocks separate and plant out very easily. Mine have worked very well. I currently have turnips and beets ready to go out. ...and some flower seedlings. I do not move my starts up into 'the next size' block - a waste of money IMO. You don't have to. Just choose a blocker of 'medium' size, and it's good for most medium seeded plants. Large seeds/seedlings such as zucchini, I still use cells, and small seeds/seedlings such as lettuce and spinach seem more efficient started in plug flats. (200s)
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greencubes
11 years ago
Hi biblion. I can understand your issues. Rest assured many are using them successfully, including me. Please check out PottingBlocks.com for some excellent help and live toll-free helpline, too! Soil blocks are fun and easy once you get over the learning curve. Takes a little practice to make nice soil blocks and germinate successfully in them. Soil blockers can be used successfully even to beginner gardeners. Hang in there!

Here is a link that might be useful: Soil Block Makers
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biblion
Original Author
11 years ago
Thanks, greencubes.
I would like to hear more about your experience germinating seed in them.
If by "learning curve" you mean actually making them, honestly? It took about ten seconds for me to figure it out.
I will go check out the website you cite, but its your experience I crave.
I have not given up. Since I originally posted I have had success with Dill, Cilantro and Chard geriminating in the blocks. However, Parsley appears to have an aversion to this medium. Parsley?
I guess what I am trying to figure out is.....
Maybe....
The only thing different about the planting media I've used is peat moss. It doesn't make sense to me, because I've seen Parsley grown in peat pots and it did well.

So, having given a lot more thought to this that it might actually merit, the only explanation I can come up with is that the intitial root system which the plants put down are either A) sensitive to the acidity of the peat or B) unable to penetrate the density of the peat.
From my own experience: its not the density of the peat. I've reduced it to a minimum. though I will experiment with reducing it more to see how little peat might be used to make blocks which hold together.......
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northforker
11 years ago
I received a soil block maker from a friend for Christmas this year. I used it with promix and had great success with both zinnia and nastursium germination.
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adodd67
11 years ago
This is my first year with soil blocks. I'm using the 2 inch. I used a seed starting mix (sunshine 360 and second time Promix) combined with compost. 3 to 2 ratio. I had a pretty decent germination rate, I think. I put 3-4 seeds per block, though, so I can't be exact, but I do have lettuce growing in every block and many require thinning. Mine did best without a germination mat and in my basement.

I was coming to the board to ask about soil blocks and the brassicas. Everything else has done very well in the blocks except the brassicas. I sold my extra seedlings, and everyone seems very happy with their plants. I am really pleased with the soil blocks so far.
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Germination Frustration with Soil Blocks

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digdirt2

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Germination Frustration with Soil Blocks

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digdirt2

biblionOriginal Author

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greencubes

biblionOriginal Author

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biblion
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