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Everything you need to know about growing tomatoes

This week I’ve started the first in a series – so for all you tomato growers or would-be tomato growers, this is for you. This one is all the background info you need to know in order to grow tomatoes successfully. It isn’t about having a greenhouse or grow lights or any of that, just a good old run-through of the stuff that’s actually important. So if you’ve been disappointed with your tomato growing in previous years, I might just be able to help.

There is absolutely no comparison between homegrown tomatoes and those you buy in the store. No comparison. The taste is just so superior in homegrown tomatoes. So given that they are actually not over complicated plants to grow, why wouldn’t you want to give it a try?

Types of Tomato

You’ll hear tomatoes described in two ways, either by the description of the actual fruit themselves. Such as cherry, plum, beefsteak, salad, or even paste tomatoes. The simple explanation of all of these is down to size and shape. Cherry tomatoes are small and round, plum tomatoes are larger and elongated. Beefsteak tomatoes are very large, salad tomatoes are the regular-sized tomatoes you would maybe slice for sandwiches, and paste tomatoes are those grown specifically to have a lot of flesh, perfect for making tomato pastes and sauces.

basket of tomatoes

The second description you will hear is to do with the growth habit of the plants themselves. Very simply, there are two main types of tomato plants. The taller plant, sometimes called vine or cordon is known as an indeterminate tomato plant. This is because it will continue to grow throughout the season, having no determined size. The second type is referred to as determinate, meaning there is a pre-determined size they will grow to and usually stop there. This is usually around the 4ft tall mark. This type of plant is commonly called a bush tomato. Now you do get variations of the bush tomato, some very small, some ideal for hanging baskets. But essentially, they are determinate.

Sowing seeds

There is nothing fancy needed to sow your tomato seeds, a warm window sill will do the job fine. Basically, your little tomato seeds need warmth (usually warm compost) and a bit of water to germinate. As those seedlings emerge they need to be kept warm and watered sparingly. The ideal temperature for the seeds to germinate is around 18c and those little seedlings themselves need to be kept above 10c MINIMUM while they are small. This temperature will need to rise as the plant grows.

One of the most common problems with sowing and growing your little seedlings is water and ventilation.

So water sparingly. Those tiny little seedlings won’t actually use as much water as you think, and sitting in wet compost just won’t do them any good. The same can be said for the general humidity around them. Propagators are fantastic for keeping moisture levels right for seeds to germinate, but once your seedlings are upright and out of the soil, take the lids off of your propagators to allow proper airflow and ventilation to stop mould, fungus and the dreaded damping off.


I mentioned that those little tomato seedlings will need to be kept warm, well as they grow that need will be more evident. Tomato plants will survive at temperatures above 10C. That includes nighttime folks so don’t think you can put your little seedlings into an unheated greenhouse in the UK in April overnight. Afraid not. I’ve learned from experience, just how detrimental the cold can be to tomato plants.

I often explain the temperatures like this. Small, baby plants need less of everything than larger producing plants. Less water, less heat, less nutrients. I know that I can sow tomato seeds in my unheated greenhouse in March and bring those plants on. They will do great. However, the tomato plants I sow in February will struggle if I do the same thing, and here’s why.

As a plant grows and starts to produce flowers in order to produce fruit, that plant needs more nutrition and water to support that production. So anything that reduces this will cause the plant stress and that stress will hamper the plant’s growth, and production and make it more susceptible to pests and disease. One of the things about how a tomato plant grows that you maybe don’t realise is that in order for that plant to get to all the lovely nutrition in your soil is that it needs both consistent temperatures (above 15c for a flowering plant) and consistent watering.

So what happens when you don’t give the plant that consistent warmth it needs? Well, in short, the plant is unable to access the nutrition in the soil that it needs. Basically, you starve the plant, and no amount of feeding it will help because the plant will just not be able to get to those nutrients, which then will cause deficiencies (think malnutrition). I’ve unfortunately seen this myself when I put my plants out into the greenhouse early and didn’t provide them with enough heat before I saw the telltale signs of potassium deficiency, purple leaves. Not all is lost though, you can reverse this by simply fixing the heat levels for your plant and soil.


Now I know you will have heard of blossom end rot, where a lack of calcium uptake in the plant causes your tomatoes to “rot” from the bottom. Well, what most people don’t realise is that it isn’t actually a lack of calcium in the soil which causes this problem, it’s actually inconsistent or not enough water. The plant needs the water to allow it’s roots to take that calcium from the soil. So even adding eggs shells, Epsom salts and other potential sources of calcium to your soil, won’t help if you don’t sort the watering. Honestly, just sorting your watering will fix blossom end rot in almost all cases. Even those times where folk have told me that they fixed it by adding calcium to the soil (in various forms), when I asked them further questions, it turned out they had also, because of the need to add items to the soil, fixed their watering issues.


Now here’s a shocker for you, you don’t need to prune tomato plants. I know, the entire internet tells you that you do! Well actually that’s not entirely true, the internet tells you the best way to manage your tomato plants and pruning is one of those things. However, no harm will come to your plants if you don’t prune them. We just do it to get the best results from our growing.

So how and what to prune then?

The main reason we prune tomato plants is to help direct the plant’s energy into producing lovely tomatoes for us. We also prune to help keep the plants healthy by encouraging airflow around the plant and in cases of bushy plants, reducing the amount of shade that that plant is in. Yes its own leaves can shade the plant and reduce the amount of sugar it will produce.

So in simple terms then, we prune indeterminate tomato plants to a single stem so that as this plant grows, it can focus its energy into tomato production rather than stem and leaf production. This is the type of pruning you’ll hear mentioned most often and you’ll hear the word suckers. Now suckers is the common name for tomato plant side shoots. You know those little shoots that grow between a leaf and the main stem? Well, those we nip out or prune off so that the plant can continue to focus on that main stem and the fruit. We do this all year, whenever we see these side shoots start to form.

We don’t do this on determinate plants (bush plants) because their growth habit is different. Bush or determinate tomato plants are allowed to grow side shoots into new stems to produce fruit because the plant will not continue to grow tall like the indeterminate or cordon/vine tomato plants. Therefore it needs all f its growth and side shoots in order to give us the best harvests.

The other type of pruning we do is later in the season once the plants are vigorous and that is to reduce foliage if the plant gets overly full. This helps to reduce shade, and improve airflow which in turn reduces the likely hood of pests of disease and allows light and heat to reach all areas of the plant and the tomatoes.

This is especially important late in the season when you want to give the plant every chance to ripen as many of those tomatoes on the vine as possible.


Pollination is the very last thing I’m going to mention here. Generally, this is not something you need to worry about too much if you grow your tomatoes outdoors. Tomato plants can self-pollinate and the wind and insects will help your plants to do this. However, if you grow your tomatoes in a polytunnel or greenhouse where there is likely to be less wind and fewer insects, you might find you get a much better harvest if you help your plants along.

Luckily it’s actually really easy to help your plants with pollination and this is due to how tomato plants pollinate.

The tomato flower actually has both “male and female” parts to it, and pollination occurs when pollen is dropped from the stamen at the top part of the flower onto the female part underneath. It’s the vibration from the wind or insects (especially bumble bees) which cause this to happen. So to help this along in your greenhouse, you can simply tap the branches holding the flowers. Simple right?

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