What is the truth about container size?

[stromato]

What is the smallest swc or sip container using soil-less mix that an indeterminate tomato can be grown in and perform well in terms of taste and at least fair in yield as generally expected for a particular plant?

Some sellers of heirloom tomatoes insist that 20gal is best and never less than 15gal. Many here describe using 5gal plastic containers. Yet others have heard that commercial growers grow vines dozens of feet long in as little as 1 or 2 gallons of mix.

Hopefully someone has grown enough containers of tomatoes for enough seasons (far more than I would ever be able to) to demonstrate the answer to this in a somewhat controlled fashion.

Thank you for sharing any results or sources.

[JamesL]

Tough question and the answer truly is IMHO - it depends.
With respect to commercial growers using 1 to 2 gallons of mix - I have both read about and seen them growing very tall single stemmed plants in that amount of mix, but they are not doing it in SIP's. Not that I have seen anyway.

In my own experience and thoughts on the matter, 5 gallon is probably the smallest SIP or SWC in which you can grow large indeterminate plants.
The issues are, in my mind and in no particular order - support, pruning, water, fertilizing and time.
Support - both for the plant and to prevent tipping over.
Pruning - 1 or 2 stem or will you just let it do its thing.
Water -Probably the big one. Big plants are thirsty. Can you keep a smaller sized reservoir filled adequately.
Fertilizing - Will a fert strip be enough or will you have to continuously feed it.
Time - All of the above require it.

An unpruned plant in a 5 gal will never be able to grow to the same size as the same plant in a larger container. Never enough root space. Nor will the yield be the same. Yields in the 5 gal are nothing to sneeze at though, as long as the plants needs are addressed.

In my mind, the primary factor for building or at least starting out with a 5 gal 2 bucket system is time and cost.
Cost - You can get food grade buckets for free, recycle a yogurt or other container as the wick, and put the whole thing together very inexpensively.
A 20 gallon SIP will use 4 times the mix as a 5 gallon, and the cost for soilless mix can add up quickly.
Time - a 2 bucket 5 gal system goes together pretty quickly. Building an Earthtainer, the best designed large SWC/SIP (using cost and results as the yardstick) while absolutely worth it, requires a bit more in the time department.

[TomatoDon]

The bigger, the better, and here's why. The larger the pot the more stable the soil temperature and moisture is. The smaller pots may very well have enough nutrients and soil mix for the roots, but the temps and moisture is going to be spiking up and down, practically on a daily basis. It keeps the plant under stress.

Those black plastic nursery containers are so hot in the summer you can sometimes barely stand to touch them. And the roots of your tomatoes are going to be touching the inside of the plastic, and the soil mix near the plastic is going to be far hotter than the natural dirt in the ground.

Also, with small pots you have to water practically every day in the hot part of summer. If you forget and skip too many days your plants will either stress or die.

If you want the most production and taste from your tomatoes, then you have to provide the most for them. It's really that simple. In my opinion 25 gallon containers would be the minimum, but I'd prefer 40 gallon. If you do the least, you'll probably get the least -- if you get anything at all.

I live in a hot part of the country and in years past have done temp experiments with different size and color containers. You can't believe how hot the soil can get when black plastic containers are exposed to direct sunlight. Get a cheap soil thermometer and try it yourself. It's quit shocking to see how hot the soil in a container can get.

I'm sure you've accidentally touched a black car or truck in the hot part of summer. It's so hot you can barely stand to touch it. That's about how it works with black plastic nursery containers, too. You can neutralize this somewhat by putting burlap around the containers, or putting hay around them.

From all aspects, the bigger, the better. For maximum yields, give maximum soil.

DS

[AKmark]

I have many heirlooms and hybrids in 10-20 gallon pots, some will have 20lbs or more fruit by the end of season. Larger pots make it easier to maintain a consistant moisture level without plants sitting in water. I have a 12ft 1884 in a 20 gallon pot, a pic is in the AK SP thread. 20 gallon easier than 10, so Don may be right about really big containers as best. I also have a few in smaller containers, it works but is tricky in hot weather.

[cythaenopsis]

I'm using a set of small SWC's, that are somewhere between 5-10 gallons (it wasn't stated on the label so I have to guess). They are light green in color. We've had a few stretches of days in the low to mid 90's, even with "real feel" close to 100. Most of the days since mid June have been peaking in the mid to upper 80's, with not much let-up at night (I think it has been about 6 weeks since we had a below 70 degree night).

I can tell you that my soil is not hot. There is a mulch layer on the top and when I stick my finger into the soil, it's cooler than the outside air. And this is near the edges, too. My containers get direct sunlight for about a good solid 7-8 hours a day.

So yes, I'd avoid using black containers. White, clay, red, or light green would be OK, IMHO.

As for size, I'm learning a lot about this myself. It does seem like heirlooms do better in 10gal and above. I just did some soil investigation in my pot and there are small roots just under the soil surface. That tells me that the plant would do better with more soil. However, I am filling up the reservoir daily. At this point it is about half depleted in one day. I have to believe the roots have found their way into that level and are drinking it, but better to top off to keep more of them happy.

Anyway, my take is that you can do 5 gallon SWC's, but just be sure to select a variety that doesn't grow very tall. The taller/longer the plant, generally the more extensive the roots. This is why it's also important to be more active on pruning with containers. If the plant tries to grow more than the container will support, it'll become stressed. Next year I am re-using these pots for hybrids and then going for larger pots to grow heirlooms.

[Tania]

I also tell everyone 'the bigger the better' as far as the pot size goes.

I grow hundreds of tomato plants every year in pots that range from 3 gal to 40 gal. Most of them end up in 5 gal pots, as this is what I have plenty. Most of the containers are black, and they do heat up significantly in the sun. So I either put lots of straw around the pots to maintain even temps and moisture level, or I put a few layers of newspapers around each pot (on the outside). It helps a lot. I have very good performance in 5 gal pots.

Having said that, the best performers in my container garden are usually the plants grown in the huge 40 pots. I put 3-4 plants into each, and they love it.

EDITED TO ADD: I never prune my tomato plants.

[Ken4230]

Originally Posted by Tania

Having said that, the best performers in my container garden are usually the plants grown in the huge 40 pots. I put 3-4 plants into each, and they love it.

EDITED TO ADD: I never prune my tomato plants.

Have you ever tried plastic 55 gal. drums cut in half? I think i may try some next year, including a couple of self waterers. I now use 4 wheeler tires with the top sidewall cut out for most of my containers.
I usually plant directly into the ground and fill up the tire as the tomato grows. They will run around 18 to 20 gal with one tomato and one pepper/eggplant in each tire. This seems to work really well for me, 5 gal. buckets not so much.

[zipcode]

With 2 plants in one 10gal container, I get around 10lb+ per plant on the more productive varieties. I think that's not bad. Planting 2 means I can try more new varieties each year.
I prune them to one stem to maximize production vs plant size.
One starting variety for cramped spaces I recommend Indian stripe. Easily the least fussy plant I tested yet, on top for production also not very tall so easier to support.

[Lorri D]

I bought a ton of used nursery pots, most range 3-10 gal. I planted tomatoes in all of them. The ones in smaller pots, I topped at 3 or so fruit trusses high. I am not concerned with production, as I have almost 70 plants. They are doing very well and do not wilt in the sun. We have been in the 90's for almost 2 weeks and they are loaded with fruit and look good. No blossom end rot etc... They do get very light speckled shade for about 2 hrs in the afternoon. Other than that, they get full sun.

[cythaenopsis]

Originally Posted by zipcode

With 2 plants in one 10gal container, I get around 10lb+ per plant on the more productive varieties. I think that's not bad. Planting 2 means I can try more new varieties each year. I prune them to one stem to maximize production vs plant size. One starting variety for cramped spaces I recommend Indian stripe. Easily the least fussy plant I tested yet, on top for production also not very tall so easier to support.

Wow, that's remarkable -- I wouldn't expect a 10 gal container to be able to accommodate 2 tomato plants in harmony. Are you doing hybrids or heirlooms? How are they positioned--do you have a kind of sub-soil division so that the roots don't get heavily intertwined?

[SharonRossy]

Thought I would give my two cents worth. I primarily container grow. This year I bought 20 and 15 gallon Hydrofarm grow bags and have some 10 gallon containers. While its true the bigger pots use more potting mixture, it also allows the tomato to really grow and personally, I have never pruned to I d'or two Stems. I figure we have a short growing season so I want to maximize as much as possible. I do prune some of the suckers or side shoots just to keep them from going too crazy, but watering in a container system is more challenging. Personally I prefer bigger pots especially because heirlooms get quite large. I put two cherries in a 20 gallon bag and regret it, so it's going to be a wait and see. Also, I have a couple of varieties where one plant is in a 10gallon container and the other is in the ground.
That being said, I have a volunteer which is growing between my deck and the stone next to our pool and I couldn't get it out. It continues to grow and it looks like flowers are starting. This should be very interesting. No idea what plant it is.

[zipcode]

Just heirlooms. I don't put any separator between them. I plant them at about 10cm from the edge of the container, and then train them toward the edge where there are bamboo poles attached to the margins of the container. This way you space the plants themselves so the leaves don't overlap.

Here's a pic. An Indian stripe and Azoychka. One from 2 months ago when they were planted out, and another from 1 week ago. There are a few big suckers there that I had to remove after. To keep things simple it's important to have one stem only, this way the roots don't grow too large, the sun can reach most leaves, and it's easy to attach to the bamboo poles.

[cythaenopsis]

^ Looking really good, zipcode. I'm definitely on board with your idea on training the plants so that there is less overlap. Looks like a great way to increase variety without sacrificing much yield.

[stromato]

Thank you all for sharing your knowledge.

ty, JamesL, for enumerating the practical issues for growing in smallish containers. “Yields in the 5 gal are nothing to sneeze at though, as long as the plants needs are addressed,” sounds good to me. What is it about the commercial growers using 1 or 2 gallons of mix to grow very tall single stem plants that can’t be imitated in a swc/sip setup? After all, I recall a hydroponics guru here saying that swc’s, like earthtainers, are really just “manual hydroponics.”

ty, TomatoDon, for warning of the soil mix temperature variation issues with smaller pots.

ty, Tania, for sharing the benefit of your experience with us. Just wondering—have you ever tried putting 8 plants in your 40 gallon containers? I’m speculating that the plants, spreading their roots through each other over 40 gallons and having the advantages of the large mass of 40 gallons of soil mix, might do much better than 8 plants each in their own 5 gallon pot.

And thanks to all the rest of you for your posts and sharing your info.

So I gather that good results have been obtained in 10 to 40 gallon containers, 5 gallon container results are not bad—possibly the lower limit, and, in general, bigger is better if cost of mix and time for construction is not a factor since the margin of error is greater and frequency of application is lower for nutrients and water in a bigger container.

Huge plants are impressive, but regarding the question of the practical lower limit of swc/sip container size, I’m curious what happens when you go smaller than the 5gallon lower limit JameL suggested. Assuming that all of the plant’s water, nutrient, and support needs can be met (liquid fertilizer daily(?), automatically replenished water reservoir), does the yield just drop off significantly in 3 gallons, for example, vs. 5 gallons? How do those commercial folks do it in 1-2 gallons? And does anyone know, at the lower limit of container size, if the plant should be pruned to one stem as the commercial growers do?

Thank you for any additional comments.

[cythaenopsis]

I think a lot of it has to do with the combination of the tomato variety (some just do better with more soil to work with) and the frequency of watering required, assuming all other things equal (like potting mix and fertilizer).

Those commercial folks doing it in 1-2 gallons have some optimized system going that involves automated watering and in-line fertilization, a bit more complicated than the usual home gardener would do. Frankly, the smaller the container you go then the smaller the reservoir and thus more frequent watering required. If you've got the time to add water 2-3 times per day during peak production, then you'd probably have reasonable success with 5 gallon containers.

Ultimately your answer will probably be best served by running your own experiment, growing a tomato variety you've selected in two or more different sized containers and observing the difference scientifically (make sure to weigh all of the tomatoes harvested).