How do I grow tomatoes?

Tomatoes are among the most rewarding things to grow because the difference between a home-grown and a supermarket tomato is enormous. They're also unforgiving about two things: cold and inconsistent watering. Get those right and most of the rest follows.

What you'll need

• Tomato seeds or young plants
• Pots and peat-free compost
• A sunny, sheltered spot or greenhouse
• Canes or string support
• High-potash tomato feed
• Watering can

Step by step

1. Sow seed indoors 6–8 weeks before your last frost — late February to March in most of the UK.2cm apart in a tray, 1cm deep, somewhere warm and bright. A windowsill works.
2. Prick out into individual 9cm pots once the first true leaves appear.The first pair of leaves are seed leaves. Wait for the second pair, which look like tomato leaves.
3. Pot on into larger pots as they grow, burying the stem deeper each time.Tomatoes root along a buried stem, so deeper planting builds a stronger root system.
4. Harden off over 7–10 days before planting out.Increasing hours outdoors each day. Skipping this checks their growth badly.
5. Plant out after the last frost, into rich soil or a large pot, 45–60cm apart.Late May in most of the UK. A single plant needs at least a 10-litre pot; more is better.
6. Support with canes or string and tie in as they grow.Cordon (indeterminate) varieties will reach 2m. Bush varieties need less support.
7. For cordon varieties, pinch out the side shoots between leaf and main stem weekly.This concentrates energy into fruit. Bush varieties are not pinched — check which you have.
8. Water consistently — regularly and deeply rather than a little and often.This is the key. Erratic watering causes split fruit and blossom end rot.
9. Feed weekly with high-potash tomato feed once the first truss sets fruit.Before that, nitrogen-heavy feed gives leaves at the expense of fruit.
10. Pinch out the growing tip after 4–6 trusses so the fruit ripens before autumn.Otherwise you get lots of green tomatoes and no time to ripen them.

Tips

• Blossom end rot — a dark sunken patch at the base of the fruit — is caused by calcium not reaching the fruit, almost always due to irregular watering rather than a lack of calcium in the soil.
• Blight is the main disease risk outdoors in a wet summer. Blight-resistant varieties exist and are worth choosing if you've had it before.
• Remove lower leaves as the plant grows and fruit sets, improving airflow and reducing disease.
• Green tomatoes at the end of the season will ripen indoors alongside a banana, which releases ethylene.

Common mistakes

• Planting out too early — Tomatoes are frost-tender and cold checks them badly even without frost. Late May is right for most of the UK.
• Irregular watering — Causes split fruit and blossom end rot — the two most common tomato complaints.
• Pinching side shoots on a bush variety — Bush types fruit on their side shoots. Check the variety before pinching anything.
• Feeding high-nitrogen fertiliser — Big healthy plants with very little fruit. Switch to high-potash once flowering starts.

Questions people ask