How to Grow Healthy Transplants on Your Market Garden: Soil Blocks, Plug Trays, and Potting Mix
By Jonathan Dysinger and John Dysinger
Updated on
Show Transcript
0:00Hi guys. In this video, we're going to be talking about how to grow healthy transplants. There's a lot of different ways to do this and a lot of mistakes
0:07can be made, but you've been doing it long enough to have a good system in place. So, talk to us about the system that you guys are using here on the farm currently for your propagation,
0:18growing transplants. Well, as I think I've mentioned before,
0:24um Elliot Coleman was kind of my mentor through his book, The New Organic Grower, and he makes quite a case for
0:34soil blocks, as the as making the healthiest transplants. And and I
0:40totally agree with that. I visited a lot of farms and in my opinion the healthiest transplants
0:49um have almost always been from soil blocks and you've done sidebyside comparisons.
0:57Yeah, we have we have done sidebyside comparisons. So purely from uh health of
1:04the transplant point of view, I think soil blocks win hands down. The challenge with soil blocks is they're a
1:11little more labor intensive and um are not so easily um automated as far as
1:21seating and stuff goes. So that's the downside.
1:25But just backing up a little bit, I would just say as a general rule, the bigger the block or the plug tray or whatever,
1:37the bigger the root ball,
1:40the healthier your transplant is going to be. So, that's that's a general rule.
1:47But then the other thing you've got to think about is that it's really all about um time and location.
1:58So or you know how much time and space.
2:02So um the bigger the block, the more time you have to deal with. you know,
2:10the the plant can get bigger and so you can hold it for say a month, 4 weeks.
2:18Um, if you're dealing with small blocks or plug trays like this 200 count plug
2:24tray, either you're going to have to supplement the fertility to keep it in
2:31here for a month or you're going to have to plant it out sooner,
2:36right? So, you got to keep that in mind as far as the size of the block, the longer you can hold it. But then, how much space do you have to grow in?
2:47You know, if you're trying to grow a lot of transplants in a fairly small space,
2:53you're going to need to go with smaller plug size or block size just to fit it all in. Yeah.
3:00So, those are the things you've got to weigh.
3:03And we actually have come up with kind of a hybrid system for most of our general transplants like our brasacas
3:12and beets and and um cucurbits,
3:20tomatoes, all those things. We still use soil blocks. Um, the one thing we're growing a whole lot of is salad mix,
3:31salenova.
3:33And so for that, we're using these 200count plug trays. And the reason for that again is a space issue, but also a
3:43mechanization issue is we have a um a drop cedar,
3:50not a vacuum cedar. I don't like vacuum seeders, but here's a drop cedar for this plug tray.
3:59And you know, with one quick click of the the wrist, you've seated 200 lettuce plants.
4:08Yeah.
4:09So, that's huge. So, we we've come up with a whole system, which maybe we
4:15should do a video on, just the lettuce planting system. I mean, we did talk
4:21about that some, I think, once, but that we use the plug trays and then we
4:28we do paper pots for a few things, but for somebody starting out, I would say,
4:36um, soil blocks is a great place to start. Um, we started with a 2-in soil blocker. And
4:44so, if somebody doesn't know what a soil block is, there might be somebody watching.
4:48Here's the blocker. This is the professional standup version. Here's some soil blocks. This is an inch and a half block,
4:57which I'm not sure why the basil was planted in there. Usually, we planted in a 2-in block.
5:05So, you're using a a flat bottom tray with drainage holes and
5:13heavy duty tray. So, you know, of course, one one other thing with with soil blocks is you're saving a lot of
5:20plastic cuz you're not dealing with flimsy trays that last a year or two and then you got to throw away. Yeah.
5:28So, you get heavy duty trays. Some of our trays have literally lasted us
5:3627 years. I mean, well, no, I guess we didn't have them the first year.
5:4226 years. Yeah, that's great.
5:46So, soil blocks are the way to go if you want the healthiest starts. Um, I suppose it's a little bit of upfront
5:55cost with that. You have to have the blocks, the blockers themselves, which are not cheap,
6:02but there are small versions. You know,
6:04this is a handheld version that, you know, is $35 or something. So,
6:13if you're Yeah, if you're just starting out, it doesn't have to cost much money.
6:18Yeah. Okay, cool. Any other final thoughts on growing healthy transplants?
6:24I know it's we just touched the tip of a very large iceberg. Yeah, there's a lot of final thoughts that we'll save, but
6:32um yeah, think about your your time and space and what system is going to work
6:42best for the space that you have and and uh yeah, cool. Last thing though, do you
6:50want to tell people what potting mix you're using?
6:55Yeah, for years we made our own potting mix which worked well but is fairly labor intensive. Right now we're using
7:04um it looks like burger but because it's French Canadian I think they say berier.
7:12Um and we use OM2 which is a fine mix.
7:18We use that for our our micro greens and our mini blocks and our uh paper pots.
7:27And then the OM6 is a more a coarser mix. This is some OM6.
7:36Um and you use that for soil blocks. We use that for soil blocks. All right. So, Bier OM1 and OM6.
7:46Yeah. One other thing, cucurbits have a reputation for not liking to be transplanted, not liking their roots
7:55disturbed. So, we use the 3-in block for our cucurbits and have had good success with that.
8:04Okay?
8:05So, you know, you you got to you got to take that into account, too, what what needs the plants have. Some plants don't
8:13mind being transplanted and others are very sensitive to it. So, those are just a few things. Great.
8:23Well, we hope this video has been helpful for you guys watching and that it will help you have more success with your transplanting in the future. Until next time, happy growing.
8:33[Music]
Soil blocks produce the healthiest transplants — healthier than plug trays in side-by-side comparisons — because roots air-prune at the block edges rather than circling inside a cell. The trade-off is that blocks are more labor-intensive to make. For high-volume crops like Salanova lettuce, 200-cell plug trays with a drop seeder are more practical. The key principle regardless of method: bigger root balls make healthier transplants, but bigger blocks take more space and time. Match your block or plug size to your space, your schedule, and each crop's transplanting sensitivity.
Every crop on your market farm starts in the propagation greenhouse, and the quality of your transplants sets the ceiling for everything that happens after. A weak transplant never fully catches up. A healthy one hits the ground running.
My dad, John Dysinger, has been growing transplants at Bountiful Blessings Farm for over two decades — starting with Eliot Coleman's soil block system from The New Organic Grower and evolving into a hybrid approach that uses both blocks and plug trays depending on the crop. Here's the system they've settled on.
What Are Soil Blocks and Why Are They Better?
Soil blocks are compressed cubes of potting mix made with a special blocking tool. Instead of growing in a plastic cell, the seedling grows in a freestanding block of soil. When the roots reach the edge, they air-prune — they stop growing rather than circling around inside a container.
That air-pruning is what makes the difference. Plants grown in soil blocks develop a denser, more fibrous root system than plants grown in plastic cells, where roots tend to circle and bind. My dad has visited a lot of farms over the years, and the healthiest transplants he's seen have almost always been soil blocks. They've done side-by-side comparisons on their own farm, and soil blocks win hands down from a plant health perspective.
The downside: soil blocks are more labor-intensive to produce than filling plug trays. You can't automate the blocking process as easily, and the blocks require more careful handling — especially when new, since they can break apart or melt if overwatered.
But for most general transplants — brassicas, beets, cucurbits, tomatoes — soil blocks are still what Bountiful Blessings Farm uses, and they're a great system for any grower starting out.
How Do You Choose the Right Block or Plug Size?
This decision comes down to a balancing act between three factors: plant health, time, and space.
The General Rule: Bigger Is Healthier
A bigger block or plug means a bigger root ball, which means a healthier, more robust transplant. That's true across the board. A 3-inch soil block produces a stronger transplant than a 2-inch block, which produces a stronger transplant than a 200-cell plug.
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But Bigger Takes More Time and Space
A larger block gives you more flexibility in timing — you can hold a plant in a 2-inch block for about four weeks before it outgrows the space. A 200-cell plug tray dries out faster and has less soil volume, so the plant either needs supplemental fertility to stay happy for a month or needs to be transplanted out sooner.
Larger blocks also take up more bench space. If you're propagating thousands of transplants in a small greenhouse, 200-cell plug trays fit dramatically more plants per square foot than 2-inch soil blocks.
Match the Size to the Crop
Some crops are more sensitive to transplanting than others, and that should influence your block size.
Cucurbits (squash, cucumbers, melons) don't like their roots disturbed. At Bountiful Blessings Farm, they use 3-inch soil blocks for all cucurbits and have had good success. The larger block gives the roots plenty of room and minimizes transplant shock.
Brassicas, beets, tomatoes — standard 2-inch soil blocks work well. These crops handle transplanting readily and don't need the extra root volume of a 3-inch block.
Salanova and head lettuce — this is where the plug trays come in. Bountiful Blessings Farm grows lettuce in such high volume that the efficiency of 200-cell plug trays makes them the practical choice. A drop seeder lets you seed 200 cells with one quick motion — no vacuum seeder needed. The smaller plug size means the plants go out to the field sooner, but with the Quick Plant Dibble and Quick-Plant Fabric system, transplanting is fast enough that it works beautifully.
What's the Best Potting Mix?
For years, Bountiful Blessings Farm made their own potting mix, which worked well but was labor-intensive. They've since switched to a commercial mix: Berger (sometimes pronounced "Berjay") OM2 and OM6.
OM2 is a finer mix used for microgreens, mini blocks, and paper pot systems — anything where you need a smooth, consistent texture in small cells.
OM6 is a coarser mix used for soil blocks. The coarser texture gives the blocks better structure and drainage, which is important since soil blocks don't have the rigid walls of a plastic cell to contain them.
Whatever potting mix you use, make sure it's appropriate for the propagation method you're using. A mix that's too fine for soil blocks will turn to mush. A mix that's too coarse for 200-cell trays will leave air gaps around the roots.
What About Plastic Waste?
One underappreciated advantage of soil blocks: they dramatically reduce plastic use in your propagation system. Instead of buying flimsy plug trays that crack and need replacing every year or two, soil blocks sit on heavy-duty flat-bottom trays with drainage holes. Bountiful Blessings Farm has trays that have lasted 26 years. That's real sustainability — not just in theory, but in practice.
The blocker tool itself is the main upfront cost. The professional standup version isn't cheap, but there are handheld versions for around $35 that work well for getting started. If you're testing whether soil blocks are right for your operation, the handheld blocker is a low-risk entry point.
The Takeaway
Soil blocks make the healthiest transplants. Plug trays make the most efficient use of space for high-volume crops like lettuce. Most successful market farms — including Bountiful Blessings — end up with a hybrid system that uses each method where it performs best.
Start with 2-inch soil blocks if you're new to propagation. Use 3-inch blocks for transplant-sensitive crops like cucurbits. Consider 200-cell plug trays when your lettuce volume justifies the efficiency gain. And invest in heavy-duty trays that will last decades rather than disposable ones that end up in the landfill every year.
Frequently Asked Questions
From a plant health perspective, yes. Soil blocks produce transplants with denser, more fibrous root systems because roots air-prune at the block edges rather than circling inside a cell. Side-by-side comparisons at Bountiful Blessings Farm consistently show healthier plants from soil blocks. The trade-off is that blocks are more labor-intensive to produce.
Two-inch blocks are the standard for most crops (brassicas, beets, tomatoes). Use 3-inch blocks for cucurbits and other transplant-sensitive crops that don't like root disturbance. For high-volume lettuce production, 200-cell plug trays are more practical despite the smaller root ball.
Berger OM6 is a coarser mix that provides good structure and drainage for soil blocks. Finer mixes (like Berger OM2) work better for microgreens, mini blocks, and small plug trays. The mix needs to hold together when compressed into a block without becoming waterlogged.
About four weeks in a 2-inch block under normal conditions. Smaller plug trays (200-cell) dry out faster and have less soil volume, so transplants either need supplemental fertility or need to go out to the field sooner. Larger blocks give you more scheduling flexibility.
Yes. Soil blocks sit on heavy-duty flat-bottom trays that can last 25+ years, eliminating the recurring cost and waste of disposable plug trays. The blocking tool is an upfront investment, but handheld versions start around $35 for beginners.
Cucurbits (squash, cucumbers, melons) are sensitive to root disturbance during transplanting. A 3-inch block provides enough root volume and soil mass to minimize transplant shock. The larger block lets the plant establish a strong root system before going into the field.
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