The simple guide to growing tomatoes in the UK

Did you know that for around a century it was widely believed, across all the British Isles, that the tomato was a poisonous fruit? Indeed, at first the Brits distrusted the tomato, and John Gerard’s Herball, or Generall Historie of Plantesof 1597 (which ended up being the most authoritative source in plants until the early 1700s) says of the tomatoes, which he called ‘Apples of Love’:

“Apples of Love grow in Spain, Italy, and such hot countries, from whence myself have received seeds for my garden, where they do increase and prosper. In Spain and those hot regions, they eat the apples prepared and boiled with pepper, salt, and oil: but they yield very little nourishment to the body, and the same damage it and corrupt it”

Nowadays the tomato has come a long way, both from the Americas to the Mediterranean and then to the UK; and from being dismissed to being appreciated and used by nearly everyone. Each Briton consumed in average 1,411,594 kilograms of tomatoes in 2011 alone. We eat, literally, a ton of tomatoes every single year!

With all this interest, we’ve found it essential here at Grow-Mate to produce a simple, easy-to-use guide for growing organically in the UK one of the most important crops in our tables. Let’s get to it, shall we?


1. The climate

The first and foremost knowledge for growing tomatoes successfully is understanding that they are a crop originally from the sunny and hot (but not humid) regions of Mexico and Central America. Consequently, their cultivation can only be stretched so far away up north before they start having troubles growing. If you, for example, live in Scotland, with its short growing season and often unreliable summers, it’s almost certain that you will have either to grow tomatoes in greenhouses or they won’t grow at all. Up to a point, no matter the number of organic fertilisers, non-organic fertilisers and other plant food (even specifically-designed tomato plant food), and no matter how much you care for them, prune them, or even kiss them before going to sleep, they will not grow outside.

So, the main thing before planting is considering if you have a greenhouse or if your climate (check it here) has around three and a half or four months of truly warm weather (anything above 10ºC works, but ideally between 15ºC to 25ºC) with six to eight hours of sunshine. If you can fulfil one of these possibilities, you’re on your way for some ripe, red and sweet tomatoes!


Map detailing the daily hours of sunshine available across the UK (annual average and in July).

You can use this chart (source) to get an impression of whether you are located in a place sunny enough to grow tomatoes outdoors, or even in a greenhouse.


2. The varieties

Only secondary in importance to being in the right climate is choosing the right varieties of tomatoes to cultivate. In terms of varieties, there’s two main types of tomato strains: determinate and indeterminate tomatoes. Determinate tomatoes are called like that because ‘terminate’ their own growing: they grow up to a point and then cease producing new leaves and steams, focusing only on producing one large load of fruits, after which they die. Indeterminate tomatoes are, as you imagine, called like that because they don’t have a final term for their growth: they keep shooting out new leaves and stems andfruits, though these mature more slowly and not all at once.

 Illustration comparing determinate and indeterminate varieties of tomatoes.

Determinate tomato varieties grow like bushes (left), while indeterminate varieties tend to grow more like vines (right). If you are growing them in regions with shorter summers it may be better to choose a determinate variety, even though you will end up with a flood of tomatoes as the season ends!

As for particular varieties, it ultimately boils down to personal choices, though you should probably look for the most cold-hardy ones, like ‘Early Girl’, ‘Better Boy’, and ‘Sweet 100’. Some people swear that cherry tomato varieties are easier to grow successfully in the British climate, because larger ones tend to taste watery and have trouble fully maturing without the appropriate hours of sun.


3. The soil

Now we move on, so to say, to firmer ground: what is the best soil for tomatoes? Well, even if they can seem picky in their climate requirements, the good news is that tomatoes have less trouble growing in most kinds of soil as long as it is fertile and rich in organic matter. Let’s break this down:

First there is the issue of how heavy your soil is; basically, how high is the percentage of clay and how well, in consequence, does it let roots grow and rainwater drain. Tomatoes tend to produce more fruits in lighter soils because their roots can grow better and take nutrients more efficiently, so a soil that has been well mixed with organic matter such as compost is best. This is directly tied to the fertility of the soil as well.

The soil is the plant’s food, so you want to assure that it is as fertile as can be. However, you should take care that in improving the nutrient content of your soil you’re not making it heavier. How does this happen? Well, for instance, through the usage of non-organic fertilisers instead of organic fertilisers. Inorganic fertilisers disturb the biology of the soil, and often kill beneficial insects as essential for you as earthworms. One of the advantages of organic fertilisers is that they not only respect the microorganisms living in the soil, but also build it up and nurture it. Our products, for example, are specifically designed to build the colonies of mycorrhizal fungi and probiotic bacteria that increase yields, reduce diseases and improve the nutritional content of your crops.

Soils that are improved using only organic fertilisers also tend to be more manageable in their pH, because you are not introducing drastically acid or alkaline material (as chemical fertilisers often do). Your tomatoes will thank you for this, as they prefer a stable pH of between 6.0 and 6.8, though they will grow in soil as acid as 5.5. The organic fertilisers also function as a slow-release plant food, that prevents imbalances in growth and tomatoes that grow too fast and break their skins due to sudden bombardment with non-organic fertilisers.


4. The planting

You can either buy tomato saplings or plant them directly from seed. If you’re planting them from seeds, the best idea is to start them using a horticultural tray or some compostable cardboard pots like these:

Tomato seedlings growing in cardboard pots, next to a window.

Place three or four seeds in each pot (or square, if you are using a tray), and keep them moist but don’t overwater: it’s better to keep them slightly in the dry side, and give them all the sun exposure they can get. Take them out after around a month or so, but only during the day if you fear that the nights might be too cold for the seedlings. After they have two or three little branches (when they are a bit taller than the biggest ones in the image above) move them to their definite spots, ensuring that they receive as much or more sun as they did when they were indoors. Plant them around 60 centimetres apart, in rows that are more or less 90 centimetres apart.


5. The care

Now, if you have chosen a determinate variety, your only care will have to keep an eye open for diseases and stake them well to a central stake (but don’t stake them too tightly, as the stems are tender!). On the other hand, if you have chosen an indeterminate variety you will have to do some extra work: pinch out, from time to time, most of the little shoots that try to come up from the base of the main branches. If you let these grow on their own, you’ll have a plant with a lot of leaves but not so many fruits. In any of both cases, take care that that the tomatoes themselves are never in contact with the soil once they begin to appear. If you’re using organic fertilisers and have cultivated a rich, living soil that is teeming with helpful creatures, you shouldn’t have any serious diseases unless there is too much rain during that summer. If something is wrong, you’ll have to identify the disease and look for a cure. Here is an interesting guide to identifying what may be affecting your tomato plants, if they seem to be sick.


 6. The harvest

Tomatoes should be picked with your own hands to prevent damaging the fruits, and using a pair of garden scissors to cut whole racemes. If your tomatoes are mature, you should eat them or store them right away; if they are still green and winter is approaching fast, you can ripen them indoors. The always-reliable John Seymour recommended the following method in his book The Self-Sufficient Gardener:

“Lay a sheet of soft felt in the bottom of a drawer in a cold room, lay a layer of tomatoes on top of it making sure none of them are touching each other, then lay another piece of felt on the tomatoes, then more tomatoes and so on. Lay the greenest at the bottom and the ripest on top. Be sure the tomatoes are healthy or you may end up with a drawer full of mould”

Remember to put the stems back in the ground or in a compost bin to turn them into plant food, and to save the seeds of the best ones for next year’s harvest! You can turn your mature tomatoes into sauce, chutney, or even dry them up in a food dehydrator and store them in olive oil for a Mediterranean treat. 

Green tomatoes ripening alongside a banana.

Some people, like Kevin Lee Jacobs at A Garden for the House, have this nifty way of ripening green tomatoes by placing them alongside a banana. Bananas naturally release a chemical called ethene, which accelerates the ripening of all other fruits and vegetables placed next to them. We invite you to share your methods with us in the comment section! Happy growing!

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