The Tomato Plant Container Size Experiment Part 1

So, around about October I begin to plant tomatoes out into their containers for the season. I usually plant the majority in the ground, but like to have container plants as well, as they often ripen quicker.

But then I am faced with the question, what size container should I use, and what happens if I use a smaller container?!

This year we find out.

Introducing the Tomato Plant Container Size Experiment

Last year I looked at what effect growing a range of different plants in different potting mediums would have on their overall growth and yield. The answer was surprising. There seemed to be little to no difference regardless of whether I used a special potting blend, Al "Tapla's" well-known 5-1-1 mix or straight off the shelf $2.50 potting mix. This flew in the face of everything I had read about soil properties and improved growth, and although by no means a conclusive experiment, it definitely was interesting to see such little difference.

This year I am going to look at how container size affects growth of tomato plants. The experiment will be simpler than last year, and will simply look at what happens to tomatoes as you decrease the container size.

Overview

I will be using three different container sizes for this experiment, and will have two tomato plants per container size, so we can see if there is wild differences in growth or yield even between plants in the same container size.

The containers I will be using are below, and from left to right are 13 liters, 23 liters and 42 liters.

By the time I has used all my soil medium, the containers were not quite full, and so I will estimate that the actual soil volume in each is somewhere between 9-11 liters, 18-21 liters and 36-39 liters respectively. 

From left to right 13L container, 23L container and 42L container (as marked on containers)

I chose a variety of tomatoes from the local hardware store, that were approximately uniform size and health. The punnet came with 8 plants, this experiment will look at 6 of those plants.

The tomatoes used in this experiment

More information, for those interested

I will simultaneously be growing other tomato plants in the ground, and in other containers which I may refer to, but these wont be used as a comparison for this experiment.

What sized container is actually recommended?

It is difficult to find a straight answer when searching for what size container to use to plant your tomatoes in, with some ranges between 10L as a minimum and up to 60L or more as being recommended. 

This site suggests 30L as a minimum stating;

I find the most important factor is volume of dirt. I use containers that hold 30 liters (7.3 US Gallons), and I find this is both the minimum but also an amount that usually works okay. More is obviously better, if possible.

This thread from GardenWeb seems to come to the consensus that 5 Gallon containers (18.9L) are sufficient, even for growing beefsteak tomatoes.

And this page from the North Carolina State University says that the range of container size is anywhere from 5 - 20 Gals (18.9L - 75L).

Why should we even care - just use a huge container!

Anybody that has planted a number of container fruits or vegetables knows that as container size increases, cost seems to exponentially go up. And the more you plant, the more you cop it.

With increased container size you need not only a more expensive container, but also more quality soil mix to fill it. As size increases so does the weight of the container, and a 60L container with soil and a plant (weighing up to 45kg itself) can be a nightmare to move around!

So the goal should be to find the very minimum container size that provides sufficient quality and quantity of yield to be worth the effort of growing. 

The soil mix used in this experiment

Despite finding in my last experiment that ordinary old potting mix performs just as well, old habits die hard.

The mix I used for this experiment is the same for all container sizes.

I started by rehyrdrating a block of coconut husk chips. I used the blocks sold at Bunnings, which go for about $12-13 and are far inferior to the chips I have used previously. They are much larger, and just seem less refined. I prefer the orchidmate brand, which can be found online.

The packet of the husk chips says that it expands to up 60L, but here it is after being wet, in a 62L container. I estimate it expands to a volume of about 30L or less.

Re-hydrated coconut husk chips

I split the husks in two even parts, and to each part added the following:

1 bag of orchid mix, which appears to be composted bark, of about 5-10mm grade.

Can be found at Masters hadware stores for about $8 per bag

1 bag el-cheapo potting mix

This is a $5 bag. Couldn't find a $2.50 bag anywhere!

2 large handfuls of organic tomato fertiliser, and 2 large handfuls of fig fertiliser, which is made up of super-phosphate, bonemeal and dolomitic lime.

Add fertiliser

Organic tomato fertiliser

Mix all together and we have our mix. It is a nice damp, loose and aerated mix that should allow for good root growth! Here is a quick vid, please excuse my shaky and unfocused camera-work!

Filled, transplanted and ready to go

After filling all my containers with my soil mix, I have transplanted my tomatoes and am ready to watch and record them grow! As the nights are still quite cool here in Canberra I will be lugging them in and out of the garage each night to protect them from any frosts.

All lined up nice and pretty!

So stay tuned. I feel I am lacking a really big container comparison, the 60L group, and I do have 2 more plants left over... so I might end up adding another two plants tomorrow !