What size pot do you need to grow tomatoes?

If you want to know how to grow a tomato plant in a pot then the first thing to work out is what size pot you need.  So what is the answer to the frequently asked question "what size pot do you need for growing tomatoes?"

To answer this we looked at lots of sources and this is what we concluded. Perceived wisdom is that the ideal pot size is 18-inch (45cm) diameter for determinate tomatoes and 24-inches (60cm) diameter for indeterminate tomatoes. That is 30L to 60L of compost. If you want to grow tomatoes like this then hop over to this blog post Grow at Home Tomatoes which will tell you all you need to know.

How to use less compost

But what if you could do it with a lot less compost - maybe 5L? We have been running an experiment to prove this is possible. We have concluded that it is not only possible but actually quite easy. Our plants have been producing vines of lovely rosy tomatoes for a couple of weeks now so its time to share the secrets. 

The Best planter for Tomatoes

The first thing you need is a Vigoroot 5L planter. This special fabric allows the roots to Air Prune. If you haven't heard of this before then it is a way to get a super efficient root system. The roots grow out from the centre and through the porous Vigoroot fabric. When they hit the air the root end dies off. This causes the plant to send more roots out from the centre. As you will see from the diagram below this means that you get lots of small effective roots rather than long pot bound roots. 

                

Watering tomatoes

Container grown tomato plants need more watering than garden tomatoes. The soil in planters heats up faster which leads to more water evaporation. For plants grown in regular pots or planters a good rule is to water until water runs freely from the bottom. Water in the morning and check the soil moisture levels again in the afternoon. If soil feels dry about 1 inch below the surface, it’s time to water again. A lack of water can stunt growth and inconsistent watering will cause splits in the fruit which allow diseases in. The watering is even more important with Vigoroot as it is porous so will require slightly more than regular pots. So we used Water Saucers

Water saucer wick

Water Saucers are simple but effective - a water container and a super absorbent capillary wick deliver water straight to the plant as and when it needs it. They are perfect for Vigoroot but can be used with any pot. The wicks can even be retro fitted to a plant already potted. They are quite thirsty plants. We are refilling our Saucer once every 3 days, adding liquid tomato Food direct into the water.

The tomato growing experiment results

So here are our tomatoes. As you can see they grew quite tall! We got the seeds from our friends at Jungle Seeds. They are an indeterminate tomato so should need around 60L of compost to grow this well. They are Rapunzel Hybrid-i, and are characterised by these amazing long, cascading trusses, each with up to 40 tasty sweet, bright red shiny cherry tomatoes that keep coming all summer long. These are picked individually as they ripen and have a superb flavour that rivals Sungold. 

 And as for those roots - the ones meeting the sides of the pots have air pruned. And the ones near to the wick have used it to seek out the water. This gives a partially hydroponic set up. With a full hydroponic set up the water needs to be oxygenated but this is not needed here. With this set up, the advantage is there is an air gap between the bottom of the pot and the water which allows the roots to access vital oxygen.

So if you are asking the question "what size pot do you need for growing tomatoes?" then the answer that Google gives you is definitely not the whole story.

click here for our Top 10 Tomato Growing Tips