How to grow tomatoes
From sowing seed indoors in early spring to picking ripe fruit in summer: how to grow tomatoes in a greenhouse, a grow bag or a pot on a sunny patio.
- Time
- About 20 minutes a week through the season
- Difficulty
- Medium
- Cost
- Low cost
- Steps
- 8
- Checked
What you’ll need
- Tomato seeds or young plants
- Peat-free seed compost and multi-purpose compost, or grow bags Search Amazon for peat free compost
- Small pots and large containers (at least 30cm across) with drainage holes
- Canes or tomato supports and soft garden twine Search Amazon for garden canes and twine
- High-potassium liquid tomato feed Search Amazon for tomato feed
- Heated propagator (optional) Search Amazon for heated propagator
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Safety first
- Outdoor tomatoes are prone to blight in warm, wet summers: brown patches spreading over leaves and fruit. Remove and dispose of affected plants promptly. Greenhouse tomatoes rarely get it.
Step by step
-
Step 1: Choose a type
- Cordon (indeterminate): tall, single-stemmed plants that need a cane or string to climb, and regular pinching out of side shoots. Most greenhouse varieties.
- Bush (determinate): compact and bushy, ideal for pots and hanging baskets, with little pruning needed. The easiest for beginners.
If you don't want to grow from seed, buy young plants in late spring.
Next: step 2 -
Step 2: Sow seeds indoors
The RHS suggests sowing late February to mid-March for greenhouse tomatoes and late March to early April for plants that will go outdoors. Seeds need around 18°C to germinate, so use a heated propagator or a warm windowsill with a clear plastic cover.
Next: step 3 -
Step 3: Pot on the seedlings
When the seedlings have their first true leaves, move each into its own small pot. Keep them in bright light at a minimum of about 16°C. If they're leggy, plant them a little deeper.
Next: step 4 -
Step 4: Plant into final positions
Tomatoes are tender, so plant outdoors only when there's no more risk of frost and nights are reliably warm. Harden them off first by putting them outside during the day for a week or two. Choose your warmest, sunniest, most sheltered spot, and space plants about 45 to 60cm apart. Put canes in at planting time for cordons.
Next: step 5 -
Step 5: Pinch out side shoots (cordons only)
On cordon tomatoes, small shoots grow in the angle between the main stem and each leaf. Pinch them out with your fingers when they're small. Tie the main stem to its support as it grows. Bush types don't need this.
Next: step 6 -
Step 6: Water and feed regularly
Water regularly so the compost never dries out completely and never stays soggy. Uneven watering causes split fruit and blossom end rot (dark patches at the base). Once the first fruits start to swell, feed every 10 to 14 days with a high-potassium tomato feed.
Next: step 7 -
Step 7: Stop cordons at the top
When cordons reach the top of their support, or have set about seven trusses (flower clusters) indoors or four outdoors, pinch out the growing tip two leaves above the top truss. This lets the plant ripen the fruit it already has.
Next: step 8 -
Step 8: Pick ripe fruit
Pick tomatoes when they're fully coloured, from mid-summer onwards. At the end of the season, green tomatoes can ripen indoors in a drawer with a banana, or be made into chutney.
Tips
- Grow bags are cheap and handy. Cut holes in the base for drainage and plant two or three tomatoes per bag.
- Basil and marigolds are traditional companions for tomatoes and look good alongside them.
- Remove lower leaves that turn yellow, and leaves touching the soil, to improve airflow.
Questions people ask
When should I plant tomatoes outside in the UK?
Once all risk of frost has passed and nights are warm, which in much of the UK means late May or June. Harden plants off first.
Why are my tomatoes splitting?
Usually irregular watering, such as a dry spell followed by a heavy watering or rain. Water little and often.
Do I need a greenhouse?
No. Bush and some cordon varieties do well outdoors in a sunny, sheltered spot. A greenhouse gives an earlier, bigger crop.
Sources
Checked 9 October 2026. We wrote this guide in our own words, using:
- RHS: how to grow tomatoes (rhs.org.uk)
- RHS: tomato blight (rhs.org.uk)
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Printed from howtoguides.uk/guides/how-to-grow-tomatoes/ · Checked 9 October 2026 · General information only. For gas, electrics, structural work, medical, legal or money decisions, use a qualified professional.