damping off
Seedlings can suffer from “damping off”, a fungal disease that attacks in overly humid conditions or if the pots or seed trays are not clean. Make sure seed is not sown too thickly to allow good air circulation.
sciarid fly larvae
Sciarid fly larvae can attack the roots of young seedlings which will suddenly cause the plant to keel over and die. This can arise if grown in a greenhouse that has harboured them from the year before, so hygiene is key! Make sure the compost is fresh when you sow your seed.
aphids & whitefly
Aphids and whitefly can cause problems in the greenhouse and polytunnel. Companion planting can help (basil, garlic, nasturtiums or marigolds), there are also biological controls such as encarsia wasps which will predate on the pests.
tomato blight
Blight is a major problem for tomatoes grown outside as it is an airborne fungus that prefers damp, cool conditions and is very hard to prevent if it is in your area. Blight causes dark blotches on the plants that will spread onto the fruits and eventually kill the whole plant.
There are some good blight resistant varieties (e.g. ‘Stupicke Polni Raine’). Indoor crops should suffer less from this disease which is also common in potatoes, so try to keep plants apart in the garden.
Keep an eye open for dark blotches on the leaves, stems and fruit and remove immediately. As the season progresses the lower leaves can be removed to allow better air circulation and ripening. Once all the fruit has set you can remove more of the leaves thus helping to avoid the problem.
tomato blossom end rot
Blossom end rot is caused by irregular watering that can lead to a calcium deficiency. Try to keep the soil moist by watering every day if grown indoors (outdoor tomatoes rarely suffer from this disease unless the soil is really dry). Also try to make sure there is good ventilation in the greenhouse or polytunnel.
tomato leaf mould
This is another fungal disease that can affect tomatoes grown indoors, but is rarely seen outside. Make sure there is plenty of ventilation and avoid getting water on the leaves – the lower leaves can often be removed to ensure this does not happen.
green back
You might find that you are getting green patches on the shoulders of your tomatoes. This is known as ‘Green back’ and can be caused by too much bright light and heat. Look into some greenhouse shading for the height of summer.
why are my tomatoes splitting and cracking?
Usually this is as a result of irregular watering, sudden watering can split the skins particularly of thin-skinned varieties. Try to ensure the soil is always moist but not waterlogged.
why are my tomatoes not turning red?
Tomatoes need plenty of sun to ripen and turn red, so if they are in a pot ensure they are in the brightest spot possible. Some varieties are designed to be yellow, orange, green or even black so make sure you label all your plants so that you know what to expect!
why are my tomato plants wilting?
If a mature plant is wilting it is usually a sign of drought – so water well, especially during hot weather especially if it is in a pot or grow bag. Occasionally something might have damaged the root. Young plants can be susceptible to sciarid fly or damping off, both of which damage the roots and cause wilt. Plants may also show signs of wilting if they are sitting in waterlogged soil.
why are my tomato plants turning yellow?
Yellow leaves are a sure sign of a hungry plant and can be a sign of magnesium deficiency. Once they are fruiting tomatoes need a weekly drink of a high potash liquid feed – seaweed fertiliser is ideal.
why are my tomato plants not flowering?
Usually this is a sign of a plant being too well fed with a fertilizer high in nitrogen, so do not start any liquid feeding until the plant is already in flower.
why are my tomato plants dying?
This could be the result of any of the above problems, or if you are particularly unlucky, a combination of them all!
why do tomato plants leaves curl?
There is a virus that causes tomato leaf curl, but that is unlikely in our temperate climate. The most likely cause in a greenhouse or polytunnel is overheating - the leaf is curling up to prevent further moisture loss.
Another more serious cause is herbicide contamination either in manure or compost, so make sure that it has come from a reliable (preferably organic) source.
why do my tomatoes have black bottoms?
This is usually caused by blossom end rot, the result of poor calcium take-up of the plant caused by irregular watering.
what is eating my tomato plants?
Not many animals will eat tomato plants as the leaves are toxic like their close relations, the potato. However, there is a caterpillar, the larva of the tomato moth, that is partial to the young leaves. They are masters of disguise so look underneath the leaves and squash the culprits.
why are my tomato seeds not germinating?
Tomato seeds are usually very quick to germinate (between one and two weeks), given warmth and moisture. It might be that the seeds are old, generally the fresher the better with tomatoes.
why are my tomatoes tasteless?
Some varieties have been grown for yield rather than flavour, so choose your varieties carefully. The most likely cause is lack of sunlight, however, which is what brings out the sugars in the fruit. If they’re in a pot move to a sunnier spot, feed with a high potash fertilizer and keep the soil moist.
why are my tomatoes hard?
If your tomatoes are ripe but have a hard core this could well be caused by temperature fluctuations – cold nights being the main cause.
why are my tomatoes mushy?
You might well be giving them too much water – try cutting back on the watering and see if that helps.
why are my tomatoes dry inside?
This can be caused by insufficient feeding. Make sure they get a weekly liquid feed of a high potash fertiliser.
