Sunday, February 15, 2009

Garden Question: Using Soil Block Makers When Starting Seeds Indoors—Yay or Nay?

4-Block and 20-Block Soil Block Makers at Johnny's Selected Seeds

So I'm thinking of buying a soil block maker, and I'd love to hear about any experiences you've had with them. Have you ever used a soil block maker? They're also called potting blocks, and I discovered them ages ago in the Johnny's Selected Seeds catalog but never actually ordered one. Then last year I read an interesting article about soil block makers in the special March gardening issue of Martha Stewart Living (which can be found online in its entirety here). When I was re-reading through that issue the other day and came across the soil blocks again, I figured it was a sign that I should finally take the plunge and just go order one already.

So what exactly is a soil block maker and why do gardeners love them? Here's an soil block intro from, which bills itself as "The world's resource for soil block gardening:"

Potting Blocks, also known as soil blocks, are free-standing compressed cubes of potting soil which hold their shape without any container. Potting Blocks are made from a zinc coated stainless steel Soil Block Maker, much like an ejection mold. The block maker metal form is packed into a tub of pre-moistened potting soil and then discharged into nice, firm, blocks with a pre-drilled seed or transplant holes formed right into the top.

Potting Blocks are used for seed starting or germination, and transplanting. They have an amazing success rate due to the volume of soil compressed in the cube. The roots are naturally "air pruned" due to the air barrier of the "container-less" cube. They become the growing medium and the container! They are used for everything; herbs, flowers, vegetables, cuttings, and other transplants.

Potting Blocks have many advantages over traditional potting methods. First, they eliminate transplant shock! The seedling and root system stays intact and protected, a "home away from home". They will not become "'root-bound". They eliminate root circling. They replace plastic pots, trays, inserts,etc. They contain more cubic volume of soil than pots of the same top dimensions. They promote great air circulation. They have a major increase in space utilization than round pots. And, studies in Europe have shown that Potting Block transplants are superior in performance than container-bound transplants.

They sound pretty great, huh? Kind of makes me wonder why I didn't start using them ages ago.

Soil block makers are available in several sizes, from itty bitty to big and pricey commercial versions. I'm thinking of starting with the 2" x 2" 4-block size, which can be used for all sorts of seedlings. If I like how it works, I'll invest in the 3/4" x 3/4" 20-block maker (pictured above) and four soil block maker inserts. Each insert makes a defined 3/4" x 3/4" impression in the 2" soil block, perfectly sized to insert a mini block. How convenient is that?

There are many economical and environmental reasons to use soil blocks when starting seeds, and the only outlay of cash is your initial purchase—unless of course you become a soil block addict and need to acquire one in every size available. Apparently making the soil blocks is a lot of fun.

There are different opinions as to the best kind of 'soil' to use when making blocks (some gardeners use compost, others say you shouldn't ever use compost), but everyone seems to agree that they're a wonderful invention. I'm looking forward to finally jumping on the soil block bandwagon—especially since I'm already behind with my seed starting this year.

Related Links:
Article About Seed Starting with Soil Blocks from Martha Stewart Living
Soil Block Makers at Johnny's Selected Seeds
4-Block Maker at Peddler's Wagon
Jason Beam's
Tips, Tricks, & Techniques on The Soil Blocker Blog
How To Make Your Own Soil Block Maker

So what seeds have you started already? And what did you start them in?

© Copyright 2009, the germinating foodie farm blog where seeing seeds sprout up—whether in containers or directly in the ground—is definitely one of the most rewarding aspects of gardening. Right after eating your bounty of course.


  1. I have not started any seeds for this season yet. I usually start my tomatoes and peppers indoors between Valentine's Day and St. Patrick's Day, but sometimes as late as the third week in March. We still have snow here in the Sierra Foothills of California, so I still have some time.

    I will definitely check out these soil blocks. Thanks for the info. Never used them. I use recycled yogurt cups for my seedlings.

  2. I'm thinking of purchasing one as well (the 2x2).

    I think I'm finally going to do it this spring. I'm planning on order mine from Peddle's Wagon so I can support the Dervaes family.

  3. I've only started alpine strawberries and herbs so far. I used jiffy pellets and peat pots for the herbs, but there are two trays of Cow Pots waiting for the tomatoes, peppers and eggplants.

    I have looked at the soil blocker with covetous eye, but since circumstances dictate that my first veggie garden will be a container garden on the front steps, I'll wait until there's an earth garden with raised beds. Thanks very much to the link to Martha's article, by the way!

  4. I've started onion and leeks so far, but in typical plastic flats. However I did buy a soil block maker for the first time this year. I bought the 1 1/2" size. Most of my plants will be fine with that size. I'll have to pot up somethings like tomatoes and peppers, but I might anyway for the 2" size. I might end up with the 3/4" and 2" at some point if I decide I love them. I'll be using them for the first time toward the end of February for my too early lettuce. I can already see a reason that I might not like them. Right now I've been turning the seed packs and rearranging them so they get even light. I won't be able to do that with the soil blocks, but time will tell.

  5. I was all gung-ho on soil blockers after reading Elliot Coleman's Four Season Harvest. He's got some great soil block recipes and always uses well aged compost in them.

    I'm also trying to start seeds this year with what I have on hand. That means no peat moss or other purchased items. I have read that you can use chopped straw in soil block but haven't tried it myself.

    And there are instructions on the web for making your own homemade soil block makers.

    Anyway, due to financial constraints and the need to keep things simple (I'm VERY pregnant), I've opted to go with Winter Sowing. I'm limited on window space anyway and this is something I can do outside. So check it out.

  6. Maybe I'm missing something. After you compress the soil into a block and eject it from the machine, there is a hole for the seed, right? Once the seed is planted, the block I assume, holds up after repeated waterings (which blows my mind cause there's no container)?


  7. I had never heard of these, but I am intrigued. So much to learn . . .

    I HATE buying plastic seed pots (and also hate finding the ripped and used ones all over the property, usually when I run over them with the lawn mower). Last year I made some pots from empty toilet paper rolls, which worked okay, but had its own problems. So I'll be interested to see how this works out for you. They've got to be incredibly messy (our seeds start life in the bathroom, which is messy enough without potting soil all over the place), but maybe it's worth it.

    P.S. Should I start using another name? I am NOT Kristin up there who is hugely pregnant. But congratulations Hugely-Pregnant Kristin!

  8. Yes, I use soil blocks for seeding. A word of warning: it's really hard to stop making the blocks. Much to the delight of family and friends, I ended up with 5x as many seedlings than I plant because it's so easy to make 20 little blocks all at one time and drop seeds in there. Well worth the investment.

  9. I have used the blocks, and am probably going to use them again this year. We had so so results the first year because I didn't have a good enough soil mixture. It held up -- sometimes too well -- the starts all started and grew to a point, then stopped and refused to grow any larger until I was able to plant them outside.

    SO. The main lesson learned is that I need to be a lot better about fall preparations (making sure to reserve some compost ahead of time for this use) or invest properly in the peat/amendments.

    We use the 4x2" blocker. You can really fit a lot more blocks than you can pots and they are much less hassle than the plastic trays. To the person who asked about watering them, we actually didn't water them from the top (that's hard!) but just set them in trays when we made them and put water into the bottom of the tray that the blocks soaked up.

  10. I'm using the soil block makers for the first time this year and I really like them! I bought the 2x2 from The Peddlers Wagon, and may make myself a 4" blocker later in the spring. I'm also using the suggested seedling soil mix (in Eliot Coleman's book). So far I've just planted onions and leeks, and they started sprouting in 2 days. The blocks have an indentation for the seeds and are holding up well. I spritz them almost daily with water, lightly. I really like the system! I've blogged more info about it at:

  11. I have spinach growing in my cold frame on the south side of the house. I haven't started anything else though. It's still too soon up here in Zone 4.

  12. Those blocks look neat but I'm avoiding starting anything indoors this year. I have already started some carrots, radishes and lettuce in my garden, and yesterday harvested some broccoli, but that's because I live in Austin, TX

  13. These sound great! I just planted my brassicas and leeks, and I can tell you, I HATE cleaning and sterilizing the plastic pots (which of COURSE I re-use each year)! I may have to get one of these!

  14. I've got these marked in my catalog too as a potential purchase. Currently I'm using up the massive stock of other stuff for seed starting however. I'm dying to know all the ins and outs for someone who is using them.

    I've got most everything started and growing well. Onionsm cauliflower, brocolli, cabbage and the like will be transplanted from seed pots to the garden within the next week or so!

  15. crazy! i had no idea this existed, something to think about.

  16. I did a lot of propagation last year (which I tediously blogged about at my and found that soil blocks were without a doubt the best way to go. I like being able to control the potting mix I use for seeds and I also like that seeds blocks allow you to really see how well you're watering. Plus, they make transplanting super-fast. I haven't bothered to buy a seed-block-maker yet, because I generally avoid buying gadgets unless absolutely necessary. I found it worked fine to just use a small, square plastic pot to form the blocks since I only do a few dozen at a time. If you're doing massive quantities at a time, then you'd definitely want to get the gadget.

  17. I will be starting my summer veggies very soon now. I will start them in newspaper pots or saved commercial plastic ones. I use a seed starting medium. I find the tiny seedlings can push up through a seed medium so easily. Tomatoes, peppers and eggplants begin their lives on a heat mat in my basement. The 6 pack cells or the newspaper pots placed in small flats, get put into a plastic bag and closed with a twister tie. Then they are placed on the heat mat. The condensation is the perfect amount of water for the unborn seeds. As soon as they pop up, they are taken to the greenhouse to live and grow until transplant time. I also save most of my own tomato seeds.

  18. Hi,
    I made an individual soil blocker last year from free plans on the internet. The blocker was easy to make and it works well. However, despite the benefits of growing seedlings in soil blocks, the technique isn't least not for this fool.

    You have probably already read the benefits about using soil blocks. Here are some of the drawbacks that I experienced:
    1. They dried out too fast.
    2. They erode when watering from with a watering can.
    3. Some of the seedlings died from damping off when bottom watering by pouring water in the bottom of the tray.

    Without a doubt, these problems were partly due to inexperience and the homemade mix used to make the blocks. Keeping them the right moisture without watering several times a day seems to be the biggest problem. Since most of the seedlings survived, I'll make some adjustments and give it another try soon. I am glad I did not buy a store bought blocker before trying this seed starting technique.

  19. This is my second season using the soil block makers and I LOVE them! I use the 2" blocks to germinate the seeds (first broccoli, cauliflower, brussels sprouts & cabbages; now tomatoes & peppers), then "pot them up" into the 4" blocks. BRILLIANT. I can't even tell you the difference in my tomato seedlings when I ran out of seed trays to hold blocks and had to finish potting up into plastic pots. The seedlings that went into the 4" blocks are a good inch taller than the ones in pots (and that's just in the first few days.) These things are well worth the investment!

  20. I'm just realizing that I posted the wrong URL for Winter Sowing. It should be:

    And I'm still very pregnant and it is nice to see someone else in the world knows how to spell "Kristin" the right way!

  21. This is my 4th season using the soil blocks. I have both the 20 microblocker andt he 2"X2" 4-block maker. I really like using them, especially the micro-blocks for early starts of peppers and tomatoes which do better on heat mats. I can fit hundreds of seeds on just 3 small heat mats and can then transfer to the 2" blocks soon after they germinate. I've written a post on my blog detailing the process. Check out and

    I'm in SE MN and like to push the seaon's limits as much as possible. By the time I can get the tomatoes in the garden in May they will be HUGE in 6 inch pots. So far I have the tomatoes, peppers, celery, okra, basil, eggplants, leeks, and onions started inside. The leeks and onions have moved to the coldframe. Brassicas are next on the seeding list.

    I got my soilblockers from Fedco seed/Organic Growers Supply. I'm hoping to get the 20-block 1.5" sometime. Not sure that I would find the 4" blocker to be worth the cost and time to make blocks.

  22. Oh, I forgot to mention that the starting medium makes all the difference in the world! I've used Eliot Coleman's recipe. It is wonderful, but takes a big of time to find all the ingredients, mix, etc. Currently I use Vermont Compost's Fort Vee mix. It is amazing. Plants do EXTREMELY well. I've tried using Scotts "organic" potting mix and it was a dismal failure. I'll never do that again.

  23. They sure do sound great. My only concern would be that some vegetables that need loose soil wouldn't do very well in these, like carrots, onion, garlic, and other root vegetables. I'd take a quick look on ebay to see how many of them are being re-sold. That way you know if other consumers liked their purchases or not.


March 2013 update: My apologies for the inconvenience - I know word verification is a pain - but I've had to turn it on to help stop the ridiculous number of anonymous spam comments I've been getting every day. Thanks for your understanding.

Welcome to! Thanks so much for taking the time to write. While I'm not always able to reply to every comment, I receive and enjoy reading them all.

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