The short answer
Tomatoes are tender, so sow them indoors in spring at around 18C, then grow them in a greenhouse or the warmest, sunniest, most sheltered spot you have, in pots, growing bags or the ground. The two keys to success are steady watering (uneven moisture causes splitting and blossom end rot) and a high-potassium feed once the first fruits set. If you are growing a cordon type, keep pinching out the side-shoots so it puts its energy into fruit.
Tomatoes at a glance
Tomatoes are one of the most rewarding crops to grow, and home-grown ones, picked ripe and warm from the plant, taste far better than anything from a shop. They need a little attention, but a warm spot and a steady supply of water will see you cropping all summer.
| Tomatoes | |
|---|---|
| Sow | Late February to mid-March (greenhouse), or late March to early April (outdoors) |
| Germinate at | About 18C (64F), in a propagator or on a warm windowsill |
| Plant out | Early summer, once reliably above 16C and the last frost has passed |
| Spacing | 45 to 60cm (18 to 24in) apart in the ground |
| In pots | One plant per 30 to 45cm (12 to 18in) pot, or two per growing bag |
| Position | A greenhouse, or a warm, sunny, sheltered spot outdoors |
| Harvest | Mid-summer into autumn |
Cordon or bush: pick your type first
Before you buy seed, check whether the variety is a cordon or a bush type, because they are grown and trained quite differently. Small cherry varieties are the easiest, fastest and most prolific if you are just starting out.
| Type | What it is like to grow |
|---|---|
| Cordon (indeterminate) | Tall, grown on a single stem. Needs a tall cane or string, regular tying-in and side-shoot removal. The widest choice of varieties, and best where you can grow upwards, such as a greenhouse. |
| Bush (determinate) | Naturally compact and bushy. Left to branch, with little training. Good for pots, troughs and the patio, and the easiest type to grow. |
| Dwarf and trailing | Small, compact or cascading plants bred for window boxes and hanging baskets. |
Sowing and planting
Tomatoes are easy from seed sown indoors, and that gives you the widest choice of varieties. You can also buy young plants in spring if you are short of time or space.
- Sow late February to mid-March for a greenhouse, or late March to early April for outdoors. Germinate at about 18C (64F) in a propagator or on a warm windowsill under a clear bag, then give the seedlings as much light as possible so they do not grow leggy.
- Pot on into individual pots once the first true leaves appear, handling seedlings by a leaf, not the stem. A leggy seedling can be replanted deeply, up to its lowest leaves.
- Plant out in early summer, once temperatures are reliably above 16C and the last frost has passed, after hardening off. Plant deeply so the first leaves sit just above the soil, as the buried stem makes extra roots.
In containers, use one plant per 30 to 45cm pot or two per growing bag of peat-free compost. In the ground, dig in plenty of garden compost, choose your warmest sheltered spot and space plants 45 to 60cm apart. Try not to grow tomatoes in the same bed two years running, to avoid a build-up of disease. For planning the beds, laying out your plot to scale first helps you fit everything in.
Watering and feeding
Steady watering is the single most important thing. Keep the soil or compost evenly moist, never swinging between bone-dry and sodden, which is what causes fruit to split and the dark, sunken patches of blossom end rot. Plants in pots and growing bags dry out fast and may need watering daily in hot weather.
Once the first fruits start to swell, feed container plants every 10 to 14 days with a high-potassium liquid tomato feed. Tomatoes in well-prepared ground may not need feeding, but a fortnightly feed still boosts the crop. A mulch of garden compost around the plants (kept clear of the stem) helps hold moisture in.
Support and side-shoots
Cordon types grow as a single tall stem and need support: tie the main stem to a sturdy cane as it grows, or wind it up a vertical string anchored under the rootball. Because tomatoes do not cling on their own, you have to attach them by hand.
The key job with cordons is removing the side-shoots, the small shoots that sprout at the joint just above each leaf. Left on, they turn the plant into a sprawling, leafy mass that fruits poorly. When the plant reaches the top of its support or has set seven trusses indoors, or four outdoors, stop it by pinching out the growing tip two leaves above the top truss.
Bush types are the opposite: leave the side-shoots to branch out, and only add a short cane if a heavy crop starts to drag the stems down.
Harvesting and common problems
Tomatoes ripen from mid-summer, earlier under glass. Pick them when fully coloured, with the stalk attached, checking every few days. At the end of the season, bring any unripe fruit indoors to a warm, dark place, or pop them in a drawer with a banana, which speeds up ripening.
- Blight is the main outdoor problem in warm, wet summers, browning the leaves and rotting the fruit. It is rare under glass, so a greenhouse is the safest bet in blight-prone areas.
- Splitting and blossom end rot both come from uneven watering, so keep the moisture steady.
- Grey mould and whitefly can trouble greenhouse plants; keep the air moving and open the vents.
Frequently asked questions
Do I need to remove the side-shoots from tomatoes?
Only on cordon (indeterminate) types. Pinch out the small shoots that appear in the joint above each leaf, so the plant grows as a single stem and puts its energy into fruit. Bush (determinate) types should be left to branch, so do not remove their side-shoots.
Why are my tomatoes splitting or getting blossom end rot?
Both are caused by uneven watering, the soil swinging between very dry and very wet. Keep the compost or soil evenly moist, water little and often rather than occasionally and heavily, and mulch to hold moisture in. Pots in particular may need watering daily in hot weather.
When and how do I feed tomatoes?
Start feeding once the first fruits begin to swell. Give container plants a high-potassium liquid tomato feed every 10 to 14 days. Plants in rich ground may not need it, but a fortnightly feed still increases the crop.
Can I grow tomatoes outdoors in the UK?
Yes, in a warm, sunny, sheltered spot, planted out after the last frost. A greenhouse gives an earlier, larger and longer crop and protects against blight, which is the main risk outdoors in warm, wet summers. Small cherry varieties crop most reliably outside.
When should I sow tomato seeds?
Sow indoors from late February to mid-March if you will grow them in a greenhouse, or late March to early April for outdoors. They need about 18C to germinate, so use a propagator or a warm windowsill.
How we checked this2 sourcesView sourcesHide
Our guides draw on expert bodies like the RHS and Garden Organic, plus experienced growers, read at source. We check every guide against those sources on the date shown, and where advice differs between them, we say so. Garden Plans is published by Limely.
- AuthorityHow to grow tomatoes, Royal Horticultural Society. Checked 22 Oct 2026.
- AuthorityHow to grow tomatoes, Gardeners' World. Checked 22 Oct 2026.
