Timely tomato tips

If you have some tomatoes in the greenhouse or on the patio things are starting to get exciting! They should be growing well and fruits will be ripening any time soon – if it ever warms up. My own plants struggled in the cool, sunless spring but they are making up for lost time now. To make sure things go to plan, here are some tips to prevent some common problems.

Watering and feeding

Tomatoes are very resilient plants but you must water and feed them if you want good crops. Firstly, they must never dry out to the point when they wilt. You don’t have to have them standing in water, in fact that is not good at all. But if they dry out regularly it will damage the plants, cause brown leaf tips and, more seriously, cause blossom-end rot. This is where the ends of the fruits become sunken and turn black. If your plants dry out every weekend when you go away, you will get very few unaffected tomatoes.

Some varieties are less prone than others and cherry tomatoes are less often affected. But plum tomatoes and the big beefsteaks are very prone.

You also need to feed. Plants are still getting bigger and they are growing a crop of fruit so they need lots of feeding right now. Feed at least once a week. You can use any high-potash fertiliser but Tomato Fertiliser is best because it will also contain the calcium which helps prevent blossom-end rot. There are many ‘brands’ and you can choose your favourite.

However, sometimes tomato plants get a bit ‘purple’ and weak looking with smaller leaves as the plants grow. This is a sign that they are short of nitrogen, the nutrient that provides what plants need for healthy foliage. This is where I would switch to MiracleGro. This general fertiliser contains lots of nitrogen to make ‘big’ plants and while not generally the best for tomatoes, it will boost overall vigour. If you want an organic alternative, choose a liquid, organic ‘vegetable fertiliser’ which will also contain more nitrogen.

Of course you may make your own ‘fertiliser tea’ with nettles or comfrey and while these contain useful nutrients they are not a substitute as a balanced fertiliser if growing your tomatoes in containers. Treat them as a tonic or supplementary feed.

At this time of year it does not matter if the leaves of your tomatoes get wet, though it is best to do this early in the day so they dry out by midday.

The weather is rather cool right now and distinctly autumnal at night so I would make sure your plants are wet by teatime to avoid any possible problems with rot at the base of the plants where foliage is rather crowded.

Next month potato blight is likely to strike, in warm, stormy weather. Then it is especially important that the leaves are not wet at night. Even later in the season you must keep the foliage dry to avoid grey mould. One of the big advantages of growing in a polytunnel or greenhouse is that you can keep the foliage dry, thus avoiding blight, so don’t ruin that by spraying your plants with water in the afternoon.


Most tomatoes are indeterminate in growth, meaning they just keep on growing. If you are growing ‘bush’ tomatoes you can ignore the rest of this paragraph.

In most cases we let the plants grow upright and develop four or five trusses (clusters) of flowers, then fruits, before we take out the growing tips. In most cases flowers produced beyond that, in September, will not produce ripe fruits by late October, when plants will die.

It is important to support the main stem and to remove all sideshoots. These grow just above where the leaf is attached to the stem. There is no reason why you might accidentally remove flower trusses because these grow directly from the stem, not in association with the leaves. You can see that in the photo above.

If the sideshoots are small, and if the plants are well watered, you may be able to snap them off, otherwise use secateurs to cut them off.

Of course you need to support your plants and I tend to use string because I can tie it to the bars in my polytunnel and I twist the plants round this as they grow. But you can use all kinds of supports – just make sure they are held securely upright.

You can remove lower leaves if they turn yellow but it won’t speed up ripening


It is very frustrating when you have tomatoes on your plants and they just don’t seem to ripen. There are many ‘tricks’ to speed up ripening but basically you will just have to wait. While it is true that many ripe fruits will produce ethylene gas, especially bananas, which cause nearby fruit to ripen, your tomatoes will not ripen until they are fully formed. Putting some over-ripe bananas under your plants or even some banana skins (don’t put them on the path) may help ripening but only a little.

What your tomatoes need is warmth for the fruits to ripen. The fruits do not need direct sun. And here is where another problem is found. Many people remove the leaves from the lower parts of the plants, exposing the fruits to the sun. This will not speed ripening. The plant needs these leaves to feed the plant. If they are turning yellow you can remove them and later in the summer, as we approach autumn, you should remove low, crowded leaves to improve airflow and help prevent grey mould. But you should not be removing many leaves right now.

Exposing the developing fruits to direct, hot sun can cause ‘green shoulder‘. When this happens the ‘shoulder’ of the fruit, the top around the stalk, becomes ‘sun burned’ and it remains green and crunchy even when the rest of the fruit ripens. This is far more common on beefsteak tomatoes than cherry types and some F1 hybrids are bred to resist the problem. The fruit are still edible and if you have holidays in warmer parts of the world you will have been served these.

Late in the season, wet plants and those in stuffy, airless conditions will be attacked by grey mould but it is not an issue yet

How long you have to wait for your first tomatoes will vary hugely. Cherry tomatoes usually ripen first. Beefsteaks are often the last to ripen and I rarely get many until mid August. By then the cherry tomatoes are in full flood. It is always worth growing a few different kinds each year, though you will probably have a favourite.

For the best flavour, let your tomatoes ripen on the plants and, ideally, eat them immediately, while still warm. And please, never put them in the fridge!

SMOKER ALERT: Tobacco is related to tomatoes and tobacco is usually infected with tobacco mosaic virus. Even when cured, the tobacco still contains the virus and smokers should take care when handling tomato plants. The virus will be on the skin and will infect the tomatoes and the disease will weaken them. So either wear disposable gloves when handling the tomato plants or clean your hands with alcohol cleanser – you might have some left over from COVID.

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