How to Grow Tomatoes from Seed in the UK: Sow-to-Harvest Timeline
Sow tomato seeds indoors from late February to April, about 6-8 weeks before the last frost, then plant out in late May or June. Plants fruit around 12-16 weeks after sowing.
Week-by-week timeline
| When | Task |
|---|---|
| Late Feb - March | Sow indoors at 18-21°C; use a heated propagator if you can |
| 1-2 weeks later | Seedlings emerge |
| 3-4 weeks | Pot on into individual pots when true leaves appear |
| Mid-May | Start hardening off for 7-10 days |
| Late May - June | Plant out after frost risk has passed |
| July - October | Harvest as fruit ripens |
Step-by-step
- Sow seeds 0.5 cm deep in moist seed compost.
- Keep warm and bright; germination takes 5-10 days.
- Move seedlings to bright light so they stay sturdy, not leggy.
- Pot on, burying stems up to the first leaves for stronger roots.
- Harden off, then plant in a sunny sheltered spot or greenhouse.
- Feed weekly with a high-potash tomato feed once the first fruits set.
Outdoor vs greenhouse
| Outdoor | Greenhouse | |
|---|---|---|
| Start picking | Later summer | Earlier |
| Risk | Blight in wet summers, cold nights | Needs ventilation and watering |
| Best varieties | Bush and cherry types | Cordon (indeterminate) types |
Pro tip: Water at the base, early in the day, and keep leaves dry to reduce disease.
Watch out: Never plant out before the last frost; one cold night can kill young plants.
Frequently Asked Questions
When should I sow tomato seeds in the UK?
From late February to April indoors, about 6-8 weeks before the last frost.
Why are my tomato seedlings leggy?
They are probably short of light. Move them somewhere brighter.
Do tomatoes need full sun?
Yes, at least six hours a day is best.
Pick your varieties: shop tomato seeds at Isle of Seeds.
