Tomato Growing Problems

Tomatoes are the nation’s favourite home-grown crop. Whether you’ve recently taken up gardening or honed your green-fingered skills over many seasons, you’re almost guaranteed a bumper harvest of delicious fruits.

Nothing beats the flavour of tomatoes picked fresh from the vine. They’re rich, juicy and intensely sweet – even supermarkets’ premium produce can’t top their taste, and home-grown tomatoes are much cheaper, too.

While tomatoes are easy to grow, nature can occasionally throw a spanner in the works. The good news is that many common problems which frustrate gardeners can easily be avoided by simple tweaks to watering and feeding their tomato plants. Follow our tomato growing guide and you’ll be sure to triumph over tomato troubles this summer!

Tomato Growing Problems

Leaves Rolling up

Growing tomatoes

CREDIT: Pixabay

Solution – When leaves curl inwards, gardeners often fear that home-grown tomato plants have been struck by disease. As long as foliage is green and healthy, and no pest infestations are evident, there’s usually nothing to worry about.

Leaf curl is often seen in late spring and early summer, when big fluctuations in day and night temperatures are common. To combat the problem, close greenhouse vents in late afternoon to retain as much warmth as possible if a cool night is forecast – then open doors and vents first thing in the morning if the forecast is for a scorcher.

keep an eye for tomato leaves rolling up

CREDIT: A13ean CC BY-SA 3.0 via Wikimedia Commons

Rotten Fruit Ends

Solution – Snacking on freshly picked tomatoes should be a treat, so discovering ugly rot at the base of fruits can be a stomach-churning experience! The problem is called blossom end rot, and it’s always the bottom of fruits that are damaged by dark, leathery patches

There’s no cure for blossom end rot, but there is a good way to prevent it. The rot is most likely to strike when soil or compost has been allowed to dry out while fruits are forming, so regular watering is essential.

Blossom end rot is most likely to strike where tomatoes are growing in small plant pots or thin growing bags. Always use a generous sized flower pot and fill with moisture-retentive compost, or buy extra-deep growing bags, as a deeper fill of compost can retain more moisture between watering. Look out for growing bags containing compost that’s enriched with calcium, which helps to prevent blossom end rot.

Tiny Tomatoes

Solution – Imagine the scene: your tomato plants flower, miniature fruits appear, and then… nothing! No-one wants a fruit the size of a matchstick head, and this weird phenomenon often leaves gardeners baffled.

The condition, which is most common in greenhouses, is called dry set and it strikes when the mercury soars. Baby fruits that fail to grow are the result of the air being too dry and hot when pollination took place.

Fortunately, there’s an easy way to prevent the problem. During hot weather, mist tomato plants with water first thing in the morning and again in the evening.

Flowers Dropping Off

Tomato flowers dropping off

CREDIT: Pixabay

Solution – When the yellow flowers of tomatoes appear, it’s a sign that the first crop of summer is on the way. If these delicate flowers snap off and drop to the ground instead of setting fruit (as often happens in hot, dry weather) it’s always a disappointment.

Misting the flowers with water in the morning, and making sure that crops are watered regularly and not allowed to dry out, is the best way to prevent flowers breaking off. Gently tapping tomato plants to aid pollination can help, too.

apply shading to greenhouse glassGreen-Topped Fruits

Solution – It’s easy to tell when tomatoes are ready to pick, as fruits turn evenly red, yellow or orange, depending on the variety. When the ‘shoulder’ of fruits – the area closest to the stalk – remains green while other parts ripen, action must be taken.

The problem is known as greenback, and areas of affected fruits remain hard and inedible. It’s often caused by too much sunlight, especially in greenhouses, so applying shading to glass is a must. Excessive heat can exacerbate the problem, so good ventilation is essential.

Greenback can also be caused by insufficient feeding. Tomatoes are hungry crops and regular liquid feeding with a high-potash fertiliser (any good tomato food will do) is vital for a healthy crop.

Split Tomatoes

Split tomatoes

CREDIT: Sheila Sund from Salem United States via Wikimedia Commons

Solution – Cracked, splitting fruit is one of the most common tomato-growing gripes. It affects greenhouse and outdoor tomatoes and is most likely to damage crops in late summer.

When soil or compost has been allowed to become bone dry, and is re-wetted by rain or watering, fruits put on a sudden growth spurt which causes their skins to split. Regular watering and taking care to ensure that the compost never becomes parched, is your best line of defence.

Ferny Foliage

Solution – If leaves of tomato plants become almost fern-like, skeletal and twisted, this is a tell-tale sign of lawn weedkiller damage. Stems can be affected, too, while fruits can appear partially hollow and distorted.

In short, tomato plants and lawn weedkillers don’t mix. To prevent damage to crops, only treat lawn weeds on still days, when weedkiller can’t be carried on the breeze, and close greenhouse doors and windows before treating nearby lawns.

It’s important to never use watering cans or any garden kit that has been used to tackle lawn weeds on tomato plants too.

don't mix lawn weedkiller and tomatoes plantsToo Many Leaves, Not Enough Fruit!

Solution – Cordon tomatoes (single-stemmed tomato plants supported by a cane or twine) are fast-growing Triffids. Plants produce vigorous side shoots, where leaf joints emerge from the main stem.

These shoots must be regularly pinched out throughout the growing season, or they’ll develop into a mass of unwanted foliage that yields few fruits. Removal of side shoots ensures that plants channel all their energy into cropping.

Bush tomatoes (short, wide types that are often grown in hanging baskets and window boxes) are lower maintenance, as they do not need to have side-shoots removed.

Tomato Blight

tomato blight

CREDIT Pixabay

Solution – We’ve saved the worst until last. Tomato blight is the bane of gardeners’ lives, striking in warm, humid, damp weather. Outdoor crops are at highest risk but tomato plants grown in greenhouses are not immune, as wind-blown spores can enter through vents and doors.

Tomato blight can destroy a healthy crop in a matter of days, with leaves quickly rotting, shrivelling and turning brown. Brown patches can appear on stems, too, while fruits quickly decay. Unfortunately, blight-ravaged plants cannot be saved and must be binned or burnt (never composted).

The best defence is to grow varieties with good levels of resistance to blight in future years. Look out for ‘Mountain Magic’, ‘Cocktail Crush’, ‘Ferline’ and ‘Summerlast’, all of which have a proven ability to beat blight.

Do you grow tomatoes in your garden? How do you keep your tomatoes healthy? Let us know in the comments.

Marc Rosenberg bio
Marc Rosenburg at Powderham Plant CentreMarc Rosenberg is a freelance garden writer and editor. A former journalist with Amateur Gardening and Horticulture Week magazines, he holds seven Garden Media Guild Awards. Marc has written for publications including The Garden magazine, BBC Gardeners’ World and RHS online.