Why do Tomato plants grow bigger in big containers?

BajaMitch · December 6, 2015

Does anybody know the biological (botanical) reason why larger containers grow larger plants than in smaller containers?

Intuitively, its easy to accept this phenomenon on the surface as "logical". But, there must be actual biological reasons for it. In all my reading, I have never come across any answers accept to say that the roots have less space to grow, reach out, extend, and often become root bound in smaller pots. Yeah, but, what "anatomically, chemically, and biologically" is transpiring to make and limit the above ground part of the plant to respond with less and smaller growth?

We all have seen illustrations that the root system for hydroponically grown plants have yielded huge plants and abundant fruit crops while having really small root balls. So, I would guess that root size alone is not the totality of why a smaller container yields smaller plants than larger containers.

I read that roots first grow out toward the container walls and when the plant root encounters the wall, that conveys a signal to the plant itself from early on. That root-wall encounter is (some how) or becomes a "signal". How the plant converts that signal into an actual physical reaction of growing a smaller plant is unknown by scientists.

Well, I am hoping that scientists DO know and that maybe some TomatoVillians in this forum have some good insights on the matter.

Cole_Robbie · December 6, 2015

The richest of soils, which will grow the largest plants with the smallest root volume, have a biology that cannot be duplicated in a container. It's too rich and diverse. In a container, there are not enough forms of life to keep all of them in check.

Generally speaking, larger roots grow bigger plants. But at the same time, there are a lot of ways to make the roots more efficient in a smaller space, which is the point of soil-building in any garden.

AKmark · December 6, 2015

Cole's last sentence nailed it.
I also would like to add, a 25 gallon container will grow a bigger plant, it has a bigger rootball, and if you feed it to max, the results come out on the other end.

However, a 10 gallon container is big enough to grow a 2-3 stem standard indeterminate tomato variety, and it will produce tomatoes consistently in full well developed trusses. If you do not prune, you are wasting water, fertilizer, invite disease, nothing is tidy, you have reduced fruit size, and management overall is horrible. I am ultra strict with pruning, it allows me to grow in smaller containers much, much more efficiently, period.
I have a friend up the road that does single stem in 6 inch rockwool, full size dutch varieties too, Tommaru Mucho, something like that. lol He gets massive yields, very impressive. Mine taste better though. lol
Anyway this works for yields, if that's what you want?

BigVanVader · December 6, 2015

I hadn't heard of that variety and looked it up, quite expensive seed.

BajaMitch · December 7, 2015

It's a well established fact that larger containers yield larger plants. The question is why.

Beneficial microorganisms in soil are relied upon to a larger extent than in hydroponic systems. In soil, microorganisms (among other things) are used to convert nutrients and fertilizers into usable ionic forms that the plant actually uptakes. In hydroponic systems, the nutrients are already supplied in right water soluble usable ionic form without having to depend on microorganisms.

Maybe the reason small amounts of soil in smaller containers yield smaller plants is that soil is not that efficient a medium for providing an adequate supply of usable nutrients fast enough and/or in large enough quantities to sustain larger plants. Because of this inefficiency of soil, larger amounts of soil are needed to adequately supply the microorganism converted nutrients to the plant and simply requires more soil to do the job than less soil. More soil means more root mass in order for the plant to encounter what it needs and be there when the nutrients are finally in the right ionic form to be uptaken by the plant.

If any of this "theory" is correct, the way to minimize the soil volume and maximize plant growth might be to start out with a high CEC soil/potting mix, load it up with nutrients and supplement the soil/potting mix periodically with liquid ferts that contain the right form of ionic nutrients that the plant actually uptakes. Sort of a "hybrid" approach combining some hydroponic-like feeding combined with a soil/potting mix.

The reason roots of tomato plants grown hydroponically are small is because of "air root pruning" which results in roots that are smaller, finer and more numerous which is itself a more efficient root system. So...a small container (3-5 gallons), high CEC potting mix, a good amount of fertilizer, supplement with some hydroponic-like liquid periodic feeding, and perforate the walls of the container while lining the inside with landscape fabric to accomplish air-root pruning...who knows...might be able to grow a large plant in a small container???

Don't know, but I will find out with next year's crop.

Ed of Somis · December 7, 2015

Kind of funny to read folks' "gospel"... on theoretical ideas about growing techniques and how nature operates.

After many decades of growing fruit and vegetables...I am still guessing on so many things related to gardening.

BajaMitch · December 7, 2015

AK, any suggestions or references or links on how to learn to prune tomato plants?

AKmark · December 7, 2015

That is a subject that you will see a wide variety of ideas floating around. Why? Because you don't have to prune a tomato plant to gets lots of tomatoes.

With that said, some don't prune, others are strict single stem pruners.

You asked me, so here is what I do
Very lightly trim off excess useless growth on determinates, or nothing at all.
Cherries, limited or no pruning, can have many branches, inner growth can be a mess if not cleaned up.
Saladettes- 5-6 branches works great, keeps fruit size up, also trim last few tomatoes from trusses if you want nicer tomatoes.
Standard-4-10 Oz or so, 2-3-4 branches works best for me
Beefsteaks/ large fruit varieties, 1-2 branches, I have done 4, but 1-2 seems best in my 10 gallon containers, I am not bound by that, but continuous production and tidyness go hand in hand to me.
We are really getting some nice yields from some varieties, so this is what is working good for us.

BajaMitch · December 7, 2015

Thanks, AK. Nothing beats experience. I am putting it in my notes.

Mac-77 · December 10, 2015

Quote:

Originally Posted by Ed of Somis

Kind of funny to read folks' "gospel"... on theoretical ideas about growing techniques and how nature operates.

After many decades of growing fruit and vegetables...I am still guessing on so many things related to gardening.

I agree.

Sometime a plant does great and dont know why.

More often it does not grow as well as expected and I dont know the reason for that either

Gardeneer · December 20, 2015

If you are growing in soil less medium, there are no microbes, micro herd, No organic food source.
You provide synthetic nutrients.
The reason for the direct co relation between the size of plants and the size of container has to do with the root restriction. Eg, a 3 gallon container cannot provide enough opportunity for root expansion as a 15 gallon soil volume. Smaller containers act similar to a Bonsai environment. , SMALLER THE ROOT, SMALLER THE PLANT.
You can supply all the nutrients to a plant in a small container but its size will be limited dictated by the size of its roots. The bigger the surface area of the roots, the bigger the amount of moisture and nutrients manufactured and delivered. It is on this principal that a root stock with a large root mass can result in a bigger plant and thus more production.

I have to mention that certain varieties are not going to benefit from a large container since they genetcally have a smaller root system. For example if you plant a Hahms Gelbe in 4 gallon or 10 gallon container there wont be a difference in plant size.

Gardeneer

BajaMitch · December 21, 2015

Thanks, Gardeneer for posting your response. Very insightful.

The DNA of a given plant determines their ultimate growth potential by design. Such DNA design contains the plant's size limitation. The plant will not, cannot grow beyond that limitation, all things being normal.

The best way to realize that growth potential and get as close to that optimal size/yield is to provide optimal conditions with regard to the grow media, fertilization/irrigation and climate. The whole point is that the plant will grow optimally if it gets only the nutrients it needs when it needs it. The roots do most all of its uptake at the root tips. If the root gets all the nutrients it needs when it needs it all within the sphere of its roots, then the roots will not grow any more, especially if there is enough air around the roots to accomplish 'air-root pruning'. As long as there is sufficient and adequate nutrient and oxygen and water near the plant, the roots will not grow beyond that. Not necessary. But what the roots will do is produce thousands of tiny capillary like root hairs which in itself means thousands of root tips to suck up the water and nutrients.

Growing tomatoes hydroponically proves the foregoing. Witness the root ball of a hydroponically grown tomato plant that has reached up to 10 or 12 feet in length and having produced a very good yield of fruit and the root ball is a mass of root hairs that are no more than 10 inches in diameter. See the video at the url that follows at the 8 minute and 5 second point in the video: https://www.youtube.com/watch?v=nXy32Dr4Z4A

The point is that it may not be the size of the container that determines the size of the plant, but whether or not the plant is efficiently getting the nutrients it needs when it needs it. Potting soil and potting mix may not be able to get and keep all the nutrients the plant needs in the sphere around the roots near the plant, but that such grow media is incapable of holding all the nutrients the plant needs in such a small volume (root sphere volume) of soil or mix and therefore the plant needs to produce longer and more roots to be in more places at one time to get its required nutrients.

I mean a large mission of microorganisms is to convert organic matter into usable immediately available nutrients (among other things) and the function of fungi is to extend the capacity of roots to benefit from its own network of the fungi itself which is in effect similar to many more micro root capillaries...all in an effort to get the nutrients the plant needs when it needs it.

The question is, is it possible to get all the nutrients and oxygen that the plant needs when it needs it for optimal growth in a small 5 gallon SWC container? My guess is...yes...I think.

What if one were to use an optimal potting mix that has a good CEC to hold nutrients, air holes on the side of the SWC lined on the inside with landscape fabric to provide excellent aeration, grow media with an optimal concentration of just the right amount of nutrients that the plant needs for optimal growth and development, grow media that has just the right balance of total porosity, water holding capacity, air space, bulk density, pH balance, etc.?

I have a strong feeling that it may well be very possible to grow large plants in a small container. Hydroponically grown plants do it all the time.

December 6, 2015	#1
BajaMitch Tomatovillian™ Join Date: Sep 2015 Location: California Posts: 84	Why do Tomato plants grow bigger in big containers? Does anybody know the biological (botanical) reason why larger containers grow larger plants than in smaller containers? Intuitively, its easy to accept this phenomenon on the surface as "logical". But, there must be actual biological reasons for it. In all my reading, I have never come across any answers accept to say that the roots have less space to grow, reach out, extend, and often become root bound in smaller pots. Yeah, but, what "anatomically, chemically, and biologically" is transpiring to make and limit the above ground part of the plant to respond with less and smaller growth? We all have seen illustrations that the root system for hydroponically grown plants have yielded huge plants and abundant fruit crops while having really small root balls. So, I would guess that root size alone is not the totality of why a smaller container yields smaller plants than larger containers. I read that roots first grow out toward the container walls and when the plant root encounters the wall, that conveys a signal to the plant itself from early on. That root-wall encounter is (some how) or becomes a "signal". How the plant converts that signal into an actual physical reaction of growing a smaller plant is unknown by scientists. Well, I am hoping that scientists DO know and that maybe some TomatoVillians in this forum have some good insights on the matter.

December 6, 2015	#3
AKmark Tomatovillian™ Join Date: Jun 2013 Location: Wasilla Alaska Posts: 2,010	Cole's last sentence nailed it. I also would like to add, a 25 gallon container will grow a bigger plant, it has a bigger rootball, and if you feed it to max, the results come out on the other end. However, a 10 gallon container is big enough to grow a 2-3 stem standard indeterminate tomato variety, and it will produce tomatoes consistently in full well developed trusses. If you do not prune, you are wasting water, fertilizer, invite disease, nothing is tidy, you have reduced fruit size, and management overall is horrible. I am ultra strict with pruning, it allows me to grow in smaller containers much, much more efficiently, period. I have a friend up the road that does single stem in 6 inch rockwool, full size dutch varieties too, Tommaru Mucho, something like that. lol He gets massive yields, very impressive. Mine taste better though. lol Anyway this works for yields, if that's what you want? Last edited by AKmark; December 6, 2015 at 05:13 PM.

December 6, 2015	#2
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	The richest of soils, which will grow the largest plants with the smallest root volume, have a biology that cannot be duplicated in a container. It's too rich and diverse. In a container, there are not enough forms of life to keep all of them in check. Generally speaking, larger roots grow bigger plants. But at the same time, there are a lot of ways to make the roots more efficient in a smaller space, which is the point of soil-building in any garden.

December 6, 2015	#4
BigVanVader Tomatovillian™ Join Date: Mar 2014 Location: Greenville, South Carolina Posts: 3,099	I hadn't heard of that variety and looked it up, quite expensive seed.

December 7, 2015	#5
BajaMitch Tomatovillian™ Join Date: Sep 2015 Location: California Posts: 84	It's a well established fact that larger containers yield larger plants. The question is why. Beneficial microorganisms in soil are relied upon to a larger extent than in hydroponic systems. In soil, microorganisms (among other things) are used to convert nutrients and fertilizers into usable ionic forms that the plant actually uptakes. In hydroponic systems, the nutrients are already supplied in right water soluble usable ionic form without having to depend on microorganisms. Maybe the reason small amounts of soil in smaller containers yield smaller plants is that soil is not that efficient a medium for providing an adequate supply of usable nutrients fast enough and/or in large enough quantities to sustain larger plants. Because of this inefficiency of soil, larger amounts of soil are needed to adequately supply the microorganism converted nutrients to the plant and simply requires more soil to do the job than less soil. More soil means more root mass in order for the plant to encounter what it needs and be there when the nutrients are finally in the right ionic form to be uptaken by the plant. If any of this "theory" is correct, the way to minimize the soil volume and maximize plant growth might be to start out with a high CEC soil/potting mix, load it up with nutrients and supplement the soil/potting mix periodically with liquid ferts that contain the right form of ionic nutrients that the plant actually uptakes. Sort of a "hybrid" approach combining some hydroponic-like feeding combined with a soil/potting mix. The reason roots of tomato plants grown hydroponically are small is because of "air root pruning" which results in roots that are smaller, finer and more numerous which is itself a more efficient root system. So...a small container (3-5 gallons), high CEC potting mix, a good amount of fertilizer, supplement with some hydroponic-like liquid periodic feeding, and perforate the walls of the container while lining the inside with landscape fabric to accomplish air-root pruning...who knows...might be able to grow a large plant in a small container??? Don't know, but I will find out with next year's crop.

December 7, 2015	#6
Ed of Somis Tomatovillian™ Join Date: Jun 2013 Location: Somis, Ca Posts: 649	Kind of funny to read folks' "gospel"... on theoretical ideas about growing techniques and how nature operates. After many decades of growing fruit and vegetables...I am still guessing on so many things related to gardening.

December 20, 2015	#11
Gardeneer Tomatovillian™ Join Date: Feb 2015 Location: NC - zone 8a - heat zone 7 Posts: 4,922	If you are growing in soil less medium, there are no microbes, micro herd, No organic food source. You provide synthetic nutrients. The reason for the direct co relation between the size of plants and the size of container has to do with the root restriction. Eg, a 3 gallon container cannot provide enough opportunity for root expansion as a 15 gallon soil volume. Smaller containers act similar to a Bonsai environment. , SMALLER THE ROOT, SMALLER THE PLANT. You can supply all the nutrients to a plant in a small container but its size will be limited dictated by the size of its roots. The bigger the surface area of the roots, the bigger the amount of moisture and nutrients manufactured and delivered. It is on this principal that a root stock with a large root mass can result in a bigger plant and thus more production. I have to mention that certain varieties are not going to benefit from a large container since they genetcally have a smaller root system. For example if you plant a Hahms Gelbe in 4 gallon or 10 gallon container there wont be a difference in plant size. Gardeneer

December 21, 2015	#12
BajaMitch Tomatovillian™ Join Date: Sep 2015 Location: California Posts: 84	Thanks, Gardeneer for posting your response. Very insightful. The DNA of a given plant determines their ultimate growth potential by design. Such DNA design contains the plant's size limitation. The plant will not, cannot grow beyond that limitation, all things being normal. The best way to realize that growth potential and get as close to that optimal size/yield is to provide optimal conditions with regard to the grow media, fertilization/irrigation and climate. The whole point is that the plant will grow optimally if it gets only the nutrients it needs when it needs it. The roots do most all of its uptake at the root tips. If the root gets all the nutrients it needs when it needs it all within the sphere of its roots, then the roots will not grow any more, especially if there is enough air around the roots to accomplish 'air-root pruning'. As long as there is sufficient and adequate nutrient and oxygen and water near the plant, the roots will not grow beyond that. Not necessary. But what the roots will do is produce thousands of tiny capillary like root hairs which in itself means thousands of root tips to suck up the water and nutrients. Growing tomatoes hydroponically proves the foregoing. Witness the root ball of a hydroponically grown tomato plant that has reached up to 10 or 12 feet in length and having produced a very good yield of fruit and the root ball is a mass of root hairs that are no more than 10 inches in diameter. See the video at the url that follows at the 8 minute and 5 second point in the video: https://www.youtube.com/watch?v=nXy32Dr4Z4A The point is that it may not be the size of the container that determines the size of the plant, but whether or not the plant is efficiently getting the nutrients it needs when it needs it. Potting soil and potting mix may not be able to get and keep all the nutrients the plant needs in the sphere around the roots near the plant, but that such grow media is incapable of holding all the nutrients the plant needs in such a small volume (root sphere volume) of soil or mix and therefore the plant needs to produce longer and more roots to be in more places at one time to get its required nutrients. I mean a large mission of microorganisms is to convert organic matter into usable immediately available nutrients (among other things) and the function of fungi is to extend the capacity of roots to benefit from its own network of the fungi itself which is in effect similar to many more micro root capillaries...all in an effort to get the nutrients the plant needs when it needs it. The question is, is it possible to get all the nutrients and oxygen that the plant needs when it needs it for optimal growth in a small 5 gallon SWC container? My guess is...yes...I think. What if one were to use an optimal potting mix that has a good CEC to hold nutrients, air holes on the side of the SWC lined on the inside with landscape fabric to provide excellent aeration, grow media with an optimal concentration of just the right amount of nutrients that the plant needs for optimal growth and development, grow media that has just the right balance of total porosity, water holding capacity, air space, bulk density, pH balance, etc.? I have a strong feeling that it may well be very possible to grow large plants in a small container. Hydroponically grown plants do it all the time.