Key takeaways
- Bury 10-15cm of bare stem at planting so the plant grows extra roots
- Switch to a high-potash tomato feed as soon as the first truss sets fruit
- Water the same amount every day, at the base, to stop splitting and blossom end rot
- Pinch out side-shoots on cordons, but leave bush tomatoes alone
- Tap flowering trusses under glass to help the fruit set
- Stop cordons at about four trusses outdoors and six to seven under glass
You can grow a tomato plant. These tips help you grow a heavier, cleaner crop from the same plant. They pick up once your seedlings are ready to plant, so they skip sowing and potting on.
The big wins are simple: plant deep, switch to high-potash feed at the right moment, water steadily, and stop the plant on time. New to tomatoes? Start with the beginner’s guide to growing tomatoes, then come back here.
Plant deep for a bigger root system
Bury 10-15cm of bare stem when you plant. Tomato stems grow extra roots wherever they sit in moist soil, so a deeper plant can take up more water and food.
Strip the lower leaves and sink the stem deep. The buried part grows extra roots within a few weeks.
Strip the leaves off the bottom of the stem first. Then dig the hole deeper than the root ball. Leggy plants can go in on their side in a shallow trench, with the top gently bent upright.
Space cordon tomatoes about 45cm apart. That gives each plant light and lets air move between them, which helps keep disease down.
When to switch to high-potash tomato feed
Switch to a high-potash tomato feed as soon as the first truss has set small fruit. Before that, the compost and a general feed build the plant. After it, potash pushes flowers and fruit instead of leaves.
The most common feeding mistake is staying on a general or high-nitrogen feed too long. You get a jungle of leaves and not much fruit. Feed weekly at first, then follow the label as the plants crop harder.
If you have a patch of comfrey, you can brew your own potash-rich feed. The comfrey liquid feed recipe shows how to make and dilute it. Grow the sterile variety ‘Bocking 14’ so it doesn’t seed around.
Gardener’s tip: Never feed a dry plant. Water first, then feed into damp compost, or you risk scorching the roots.
This is what high-potash feeding is for: well-filled trusses rather than a mass of leaves.
Water steadily to stop splitting
Steady watering prevents two common faults: splitting and blossom end rot. Both come from an uneven supply. A plant that dries out then gets a soaking swells its fruit faster than the skin can stretch.
Water at the base, not over the leaves, and give the same amount each day. A mulch keeps the soil evenly moist.
Water at the base, ideally in the morning, so the leaves stay dry. Give roughly the same amount each day, and more in hot, sunny spells. Grow bags dry out fastest and may need watering twice a day in a heatwave.
A 5cm mulch of garden compost or grass clippings keeps the soil evenly moist and the roots cool. If your fruit is already cracking, the guide to tomatoes splitting on the vine explains what to do next.
Pinch out side-shoots to keep one strong stem
Cordon tomatoes grow a side-shoot in the joint between each leaf and the main stem. Left on, each one becomes another stem that shares out the plant’s energy. Pinch them out at 2-3cm long, when they snap off cleanly.
Check plants twice a week in June and July, as shoots grow fast in warm weather. Leave bush tomatoes alone. They are meant to branch, so removing their side-shoots cuts the crop.
The guide on how to pinch out tomato side-shoots has close-ups of exactly where to snap.
Catch side-shoots while they are small. They snap off cleanly and leave only a tiny wound.
Strip lower leaves to cut blight and grey mould
From late July, remove the leaves below the lowest ripening truss. This lets air move around the base of the plant, where damp air sits and disease starts.
Take two or three leaves a week rather than stripping the plant in one go. By September you can clear all foliage below the ripening trusses, so more sunshine and energy go to the fruit. Cut cleanly and bin the leaves if blight is about. The guide to tomato blight prevention and treatment shows what to look for.
Help greenhouse flowers set fruit
Tomato flowers pollinate themselves, but the pollen needs a shake to fall. Outdoors, wind and bees do this. In still greenhouse air, flowers can drop without setting.
Tap the flowering trusses with a finger or a cane around midday, when the air is driest. Some growers hold a vibrating electric toothbrush against the truss stalk for a second or two. Either way, do it every day or two while plants are in flower. The hand pollination guide covers tomatoes and other crops.
Keep the greenhouse ventilated too. Open vents and the door when it climbs above about 25C. In very hot conditions, above about 30C, flowers often drop without setting.
When to stop tomato plants
Stopping means pinching out the growing tip two leaves above the top truss you want to keep. The plant then stops climbing and puts its energy into the fruit it already has.
UK summers are too short to ripen endless trusses. Stop outdoor cordons at about four trusses, usually in mid to late July. Stop greenhouse cordons at six or seven. Later trusses rarely ripen before the weather cools in autumn.
Spot and fix magnesium deficiency
Yellowing between the veins of older, lower leaves, while the veins stay green, usually means magnesium deficiency. Heavy potash feeding can make it worse, because potassium competes with magnesium.
Yellow between green veins on older leaves usually means magnesium is short. Healthy leaves above stay dark green.
To fix it, spray the leaves with Epsom salts (magnesium sulphate) at 20g per litre of water. Do it on a dull day and repeat every couple of weeks while the symptoms last. This is a plant food, not a pesticide.
Don’t mistake it for other problems. Nitrogen shortage yellows the whole leaf, starting with the oldest. Blight makes brown patches that spread fast in damp weather.
Support every truss and stem
Heavy trusses can kink or snap before the fruit ripens. Once fruit reaches marble size, cradle each truss with a plastic truss clip or a loop of soft twine tied to the support.
Support the main stem from the start. Twist it gently around a string anchored above and pegged at the base, or tie it to a 1.8m cane every 20cm or so.
Strings and steady spacing keep a row of cordons upright, airy and easy to work along.
Pick varieties for what you want
Your choice of variety sets the ceiling before any technique applies. F1 hybrids tend to be heavy, even croppers. Heritage types often trade some yield for flavour and unusual colour. The best tomato varieties for the UK guide goes into more detail.
| Variety | Type | Best for | Where to grow |
|---|---|---|---|
| ’Sungold’ F1 | Cherry cordon | Very sweet, heavy cropper | Greenhouse or sheltered outdoors |
| ’Shirley’ F1 | Medium cordon | Reliable, early | Greenhouse |
| ’Gardener’s Delight’ | Cherry cordon | Flavour, dependable | Outdoors or greenhouse |
| ’Crimson Crush’ F1 | Large cordon | Blight resistance | Outdoors |
| ’Black Krim’ | Heritage beefsteak | Colour and flavour | Greenhouse |
Tomato care calendar from planting to picking
This calendar picks up after sowing. Shift jobs about two weeks later in Scotland and the north. For sowing and planting dates, see the timing guide linked at the end.
| Month | Main jobs |
|---|---|
| April | Plant greenhouse tomatoes deep once nights stay mild under glass |
| May | Harden off and plant outdoor tomatoes after the last frost. Start pinching side-shoots |
| June | Switch to high-potash feed as the first truss sets. Tap flowers under glass |
| July | Stop outdoor cordons at about four trusses. Start removing lower leaves |
| August | Stop greenhouse cordons at six or seven trusses. Support heavy trusses. Ventilate well |
| September | Clear leaves below ripening trusses. Keep watering steadily |
| October | Pick the last fruit before frost and ripen green ones indoors |
Common mistakes that cost a crop
Too much nitrogen. Staying on a leafy feed after the first truss gives lush plants and little fruit. Switch to high potash once fruit sets.
Erratic watering. Drying out then flooding causes splitting and blossom end rot. Steady is better than more.
Wetting the leaves. Watering over the foliage in still, damp weather invites blight and grey mould. Water at the base.
Pinching bush tomatoes. Bush types carry their crop on side-shoots. Check the label before you pinch.
Not stopping the plant. Late trusses outdoors rarely ripen and draw energy from the fruit lower down.
Frequently asked questions
What is the best feed for growing tomatoes in the UK?
A high-potash liquid tomato feed, started once the first truss sets fruit. Potash pushes flowers and fruit rather than leaves. Feed weekly at first, then follow the label as the crop builds in July and August. Always water first and feed into damp compost.
Why should you bury tomato stems deep when planting?
The buried stem grows extra roots, so the plant takes up more water. Strip the lower leaves and plant 10-15cm deeper than the pot. Leggy seedlings can go in on their side in a shallow trench, with the tip bent gently upright.
How often should you water tomatoes to stop them splitting?
Water a steady amount every day rather than in fits and starts. Splitting happens when a dry plant suddenly gets a soaking and the fruit swells faster than its skin. In hot spells, grow bag plants may need watering twice a day. A mulch helps keep the supply even.
Should you remove lower leaves from tomato plants?
Yes, remove leaves below the lowest ripening truss from late July. It lets air move around the base, which helps against blight and grey mould. Take two or three leaves a week rather than stripping the plant at once.
How do you get more tomatoes from each plant?
Feed high potash, help pollination and stop the plant on time. Pinching out side-shoots keeps a cordon’s energy on one stem. Tapping trusses under glass helps flowers set. Stopping at the right truss count means more of the fruit ripens before autumn.
When should you stop tomato plants?
Stop outdoor cordons at about four trusses and greenhouse ones at six or seven. Pinch out the growing tip two leaves above the top truss. Outdoors this is usually mid to late July. Later trusses rarely ripen in a UK autumn.
Want to get the timing right from the start? Read the guide on when to plant tomatoes in the UK, or browse more growing guides for the rest of your plot.
Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
