One advantage of starting with small pots is that you have much less to care for at the start. Four one inch pots fit in the space of one four inch pot. The ratio of volumes is even more dramatic, maybe 12:1 or 16:1. It may not seem important but there is a significant difference in the effort needed for watering and moving plants around if necessary.

I believe potting on is beneficial to plant growth although I can't come up with clear reasons. They just seem to get a boost from repotting. An overpotted plant often seems to languish.

Your current thoughts seem right to me.

Jim

jimster - I read that using a bigger pot at the beginning may cause the plant to put more energy into roots at first. So I was thinking, maybe you just don't see any progress because it's all under the surface? But I'm wondering if that actually effects the final productivity of the plant. I could see more root growth now being a benefit later on, even if you can't see it. But then again, maybe top growth is more important in the beginning? I read something that Eliot Coleman wrote, back in the 1980's I think. And he said a study was underway on the effects of potting up. And he seemed to think it ultimately made the plants more productive. But I couldn't find anything about the results of the study. And no mention of it in his book "The New Organic Grower", published afterward. Although, he still recommended potting on for better use of space, etc. So it makes me wonder if it's one of those things that appears to help, because you see more top growth. But ultimately doesn't affect final production, since what you didn't see--root growth--was just as beneficial, if not more. I could see it going either way.

I read that using a bigger pot at the beginning may cause the plant to put more energy into roots at first.

The general consensus is that it is just the opposite - smaller is better for root development. It certainly is IME.

As to the many advantages to the plant of potting-up or "staged transplanting" there are umpteen discussions about it on several different forums here including links to studies, photos, etc. so I hope you don't mind if I don't re-type all of it here. A search using those terms will pull them up for you. FWIW - Staged-transplanting is what professional growers do and it has been done to the transplants you buy. But the best way to convince yourself is to do your own comparison between plants that have and those that have not been stage-transplanted.

There are no claims made to increased production as that is not the primary goal and too many other variables affect that. However one can, under normal growing conditions, expect that increased production would result from a healthier plant, a better plant circulatory system, a plant with shorter node lengths, and one with a much more developed root system.

Please note that studies and experiments done were done with increased size of cells/containers, NOT with soil blocks. Given the air pruning of roots effect of soil blocks the benefits of staged-transplanting might be compromised.

Dave

digdirt - Thanks. I've never heard the term "staged transplanting", so I didn't know what to search for. I'd expect a healthier plant to produce better. So if it gives me a healthier plant, it'd be worth the extra step. So that just leaves the question about whether or not it's the same for blocks as it is for pots. I'll do a little more research, and see what I can find.

search 'potting-up' too.

Dave

Another consideration:

Tomato plants started under lights undergo a transformation when set out in the garden. They put on a lot of growth very quickly. Soon, new growth dominates the plant to the point where branches of the original seedling are no longer significant. Small plants often catch up with larger ones in a short time. IMO, there is not much point in striving for large transplants.

Jim

dave and jim - I did a little more reading, and this is how I understand it so far...

When a seed sprouts, it sends it's taproot down as far as it'll go. It also sends out laterals on the way. Then when it can't go any farther, it kinda stops. In a pot or block it may swirl around the bottom looking for a place to go. And most root production slows down at this point. If it were planted in the garden, the taproot could keep going a lot farther. And then maybe it naturally reaches another point in its root development where it starts filling out space for a denser root structure. So that's one of the differences between planting in a small pot or block, and planting directly in the garden. In the garden, the taproot can keep going deeper, and develop fully.

When it's potted up, or transplanted, the taproot gets damaged, and that causes a different type of root to start growing. This is a more fibrous root, and goes all over the place. So the pot or block fills up more quickly with a fibrous root system, as opposed to sitting there while the taproot doesn't go anywhere.

I don't know if that's correct, but it's what I'm understanding so far. Soil blocks and pots are different. But the soil block is like a pot on the bottom, since it's probably sitting on a hard surface, instead of being exposed to the air. And disturbing that may damage the taproot in the same way.

And as for final block size, I may go with a 3 inch instead of 4. Since, like jim said, the plant may quickly make up for that smaller block once it's transplanted to the garden. And there's a significant difference in indoor space requirements, and amount of soil stuff, between 3 and 4 inch blocks.

I'm thinking about just potting up once, since it won't take as long as twice. And I may already be damaging the taproot when moving it from the paper towel where it sprouted, to it's first soil block. So it may be like the first potting up.

Yeah you got the basics. :) Those fibrous roots that develop as a result of transplanting are feeder types - both nutrients and water - and able to draw both from a larger area. While tap roots are predominately water roots.

And the tap isn't really terminated - it develops tap branches - so again better able to draw moisture from wider area than single tightly coiled tap would.

And to reiterate Jim's point - the goal isn't large transplants but plants with well developed root structures capable of supporting the spurt in top growth that happens when transplanted to the garden.

Dave

I plant into soil blocks. For tomato seeds I use the smallest block maker I have seen and it creates 20 blocks in an area about 3 x 4 inches, so I think they are 3/4 inch. I put the 20 blocks onto a square of aluminum foil in a seed tray so I can pick up the entire set of blocks and move it if it germinates faster than the others in the tray. I do not presprout. I put the seed directly into the wet block that I have just formed. I cover with a dome and keep in a warm place until I see germination starting to occur. At that point I uncover and put under lights. When the seedling is about an inch or inch and a half tall I pick up the block and plant it into a five once cup or small pot. At that point the roots will already be reaching into the other blocks around it but you can separate them fairly easily.

This year I was busy and waited a little too long and they had a mass of solid roots under the set of blocks so it took a little more effort to separate them. A plant that was only an inch and a half tall had roots 3-7 times the length of the seedling that was showing above ground.

One of the advantages to potting up more than once is that you can plant deeper each time and roots will continue to form on all of the stem that is underground. Some people grow such 'leggy' transplants that they find this a necessary step. I grow under lights, and I keep the room cool and I don't have a problem with the plant trying to stretch toward light and get leggy.

If they start getting too many roots, or the weather isn't warm enough for planting I may pot up one more time.

For seeds like melons or cukes, I use another block maker that is about 2 inches.

I love my block makers. This year I had a lot of tomato seed that I only wanted 5 plants from so I put a strip of five on a piece of mini blind that I had already written the name on.

Out of curiosity how much does this block maker cost? Is it competitive to make these soil blocks when you can buy four inch square 3.5 inch deep plastic pots for six cents each if you buy them by the case? Then you have to pay for the potting soil to fill them, which would come to about 25 cents each for the best stuff you can buy. Do you use soil from your garden or store bought potting mix to make the blocks?

Fwiw I haven't bought pots in years - lots of freebies from freinds and family, sanitized before use.

Good discussion here gang.

I use the same potting soil whether I use a soil block maker or a pot. This year it is ProMix. The small block maker makes tiny blocks so they take up very little space until I know for sure that germination has occurred, then I pot them up. The block makers I use are the top two on this page. I have had them for 10 years or more.

Here is a link that might be useful: Johnnys

I looked at Johnnys slide show and video about soil blockers linked by soonergrandmom and then went back and carefully read soonergrandmom's previous post. It is highly interesting. I can see myself adopting this system.

Jim

I have started a few seeds from soil blocks this year, tomato pepper, and cabbage. all grew well and I have potted on all of them. I simply put them in a bigger pot and added soil around the blocks. I use a homemade block maker that is 1-1/8 inch i.d. Made from a Ziploc Vacuum pump. They look like a large syringe And cost 3-4 bucks and come with 3 one quart bags. Germination has been around 98% and I just use seed starting soil.Johnys' select seeds have the best info I have found. Annys'granny has some info to as does J. Best. Best left this forum but Annys' granny is still active. Sorry I do not do pictures I am a computer Illiterate. Hope this helps some, My potted on plants are looking good so far! XXCurt~ P.S. I started the seeds in the blocks instead of paper towel/coffee filter.

dave and jim - Yeah, I think I'm getting it now. What I need to focus on is growing healthy plants, with good root structures, that are capable of rapid growth once they're transplanted into the garden. I don't need to worry as much about plant size at transplant time, since it isn't all that important. Besides, trying to manage lots of larger plants could be difficult, not to mention expensive. So it's probably not worth it.

soonergrandmom - I had some hard to germinate tomato seeds last year. And the paper towel method worked really well for those. So I decided to do them all that way this year. Unfortunately, I forgot how tedious it was getting small tomato sprouts separated from the towels after they germinated. Especially if you don't get to them right away. I was trying to follow the farmer's almanac moon planting schedule. And the only way I could do that was to start all 2000 seeds in paper towels at the same time. You can probably imagine the mess I have now:) So it's time for plan B. I did a little more research on moon phases. And I'm not so sure the tidal forces, and moonlight, will have an effect in a controlled indoor environment. So I'm going to pick a range of days, and plant new seeds directly in blocks.

The thing that sold me on blocks vs pots, was the idea that your plants don't get rootbound. So transplant shock (whatever that is) is minimized. I read that when roots run into a pot, they start circling. But when they reach the edge of a block, they just sit there waiting. And when they're potted up, or transplanted, they immediately take off. Whereas a rootbound potted plant might take some time to get going. So if you're potting up into pots, you're probably losing that advantage. Of course you may have other reasons for using pots, and the root thing may not be all that important to you.

californian - I made my blocker out of cardboard and duct tape. The cardboard was free. And I don't remember what I paid for the duct tape:) If you happen to have a pot of the right size. Or a plastic cup. You could use that just to try it out.

I tried some pro mix, mixed with compost, just to see how it would hold together. And it worked great. But I want to use coir instead of peat, so I'm mixing up my own. I adapted a recipe from Eliot Coleman. But I left out the garden soil, since I'm not so sure about mine. But I may experiment with adding it in next year. So far my coir blocks seem to be holding together. Not as well as the peat-base pro mix. But I think they'll work.

curt - Yeah, starting small seeds in paper towels wasn't such a good idea:) I'm only going to do it for hard to germinate seeds from now on. Although I don't have the same problem with larger seeds, like peas.

Tell me, are blocks made of nothing more than wet seed starting mix? Nothing special is done to keep them from crumbling apart? Such as strongly compressing the blocks for instance?

From Johnny's video I get that the mix should be quite wet.

Jim

Tell me, are blocks made of nothing more than wet seed starting mix? Nothing special is done to keep them from crumbling apart? Such as strongly compressing the blocks for instance?

From Johnny's video I get that the mix should be quite wet.

Jim

Hey! It's possible to double post, if you really try!

Jim

As far as I can tell, you just load the wet mix into the block "maker" and squeeze the handle. Pressure forms them into blocks and the wetness keeps them together. Obviously, they aren't going to stay together with lots of movement and bumping, but most people don't try to germinate seeds where they will be frequently bumped.

Only ever used the small one Jim but same seems to hold true for the bigger ones too given the many posts I have seen here over the years about what mix to use.

It can't be a coarse mix. Needs to relatively fine sifted texture to hold together. ProMix BX works well as does plain old Jiffy mix but the ones like MG Potting Mix with the bark and larger chunks in it don't seem to hold together.

Dave

jimster - This is only my first time using blocks, so I'm not the best one to give advice. But so far they seem to be holding together. Like Dave says, your mix shouldn't have large chunks. I tested pro mix mixed with compost, and those blocks held together really well. But I wanted a coir based mix, so I mixed my own. That mix uses about 1/2 coir, 1/4 perlite and 1/4 compost, plus a small mixture of amendments. Those blocks aren't as solid as the pro mix/compost blocks. But so far they're doing ok. I messed up with my seed germination, but I'm keeping some of 'em so I can experiment with the blocks. I'm going to start over on the 12th when the moon's in a better place:) I added a link to an ebook on soil blocks.

Here is a link that might be useful: link to ebook on soil blocks

And here's a link to the page where I got the link to the ebook. And btw, I'm thinking of switching from perlite to sand next time, since the perlite generates a lot of dust when its dry.

Here is a link that might be useful: link to page where i found the link to the ebook

One more link. This is the recipe I modified to come up with my coir mix. I left out the garden soil, since I wasn't too sure about mine. I think it's originally from Eliot Coleman.

Here is a link that might be useful: recipe for soil block mix - probably from Eliot Coleman

And I forgot to add... I use a really wet mix. Then stuff it into the blocker. My blocker is just like a hollow square tube, with a plunger. So when I push down on the plunger, it kinda compresses the block, squishing out the extra water. And it may also eliminate any big air spaces. Most blocks come out good the first time. Any screw ups just get thrown back in the bucket with the rest of the unblocked mix. Sorry about all the messages. An edit feature would be nice:)

I have already done all of my tomatoes and they have a much longer set of roots than these, but maybe you can she the process with these peppers. You may be able to see that these plants are just beginning to get their first real leaves. You can barely see them starting. They were on small pieces of foil so I could easily move them around or pick them up.

Full 3 x 4 inch block

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Bottom of the full block

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Breaks off easily into separate blocks

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I planted 20 seeds in 20 blocks and got 17 transplants from a tiny 3x4 space.

I did this last night and for some reason it isn't here.

I don't have any tomatoes left to do, but maybe these peppers will give you the idea. My small block maker makes 20 small blocks that fit into an area about 3x4 inches. I use this size block maker for both tomato seeds and pepper seeds, and many other small seeds.

I unmold it onto a small piece of aluminum foil so that I can move it around or remove it easily if it needs to be potted up before it's neighbors. I plant one seed in each of the 20 blocks.

Peppers with real leaves just starting

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Bottom of the block at potting-up time

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Easily separates into small blocks

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I had 17 peppers from the block of 20 in a space of 3x4 and very little potting soil involved.

I logged on and it wasn't there. Now it's here twice. Go figure. So sorry.

NP - next time hit the refresh button instead. Logging on again only brings up the same page as before from your cache.

Dave :)

soonergrandmom - I like your aluminum foil method for germinating. It looks easier than my garbage bag, cardboard, duct tape trays. I got a couple of those plastic trays, but didn't use them because of the ridges in the bottom. But the foil fixes that problem.