When to plant tomatoes?
Sow tomatoes indoors at about 18 °C: February to March in the north and centre, and from January in the south if you have warmth and plenty of light. Plant them outside once temperatures stay above 16 °C, usually from May in the north and from April in the centre and south.
When, by region
| Stage | North | Centre | South |
|---|---|---|---|
| Sow indoors | February to March, at about 18 °C with plenty of light. December and January are too early. | February to March. January only if the weather allows it, not December. | From January in mild areas, at about 18 °C with plenty of light. Without heat, February. |
| Plant outside | May to June, in the open ground. | April to May, in the open ground. | From April. Earlier only in the mildest spots, under cover, and never while nights are cold. |
Indicative months. Plants go outside only once temperatures stay above 16 °C, even if the calendar month has arrived.
Northern months come from the Valle d'Aosta calendar (sow indoors in February–March, transplant in May–June). Central months come from the Umbria sowing calendar: standard indoor sowing in February–March, January only as a mild-weather extension, and outdoor planting in April–May. The south starts earlier than Umbria, but January only in a warm seedbed. Germination and planting temperatures are from the RHS. The indoor method is in the guide to starting seeds indoors.
When to sow tomatoes
Sow in modules or small pots, somewhere warm, not in a cold bed. The RHS gives about 18 °C (64 °F) for germination: a windowsill gets cold at night, and without light the seedlings grow thin. Once the first true leaves show, pot them on and keep at least 16 °C (60 °F). Read the planting calendar next to your own frost, not instead of it.
After about a month the seedlings are tight in their pots and need potting on. They still wait to go outside until the cold is over, even if they are already tall.
When to transplant
The RHS plants tomatoes out once temperatures stay reliably above 16 °C (60 °F), after hardening them off for a couple of weeks. Set them a little deeper, so the buried stem grows extra roots, in the sunniest spot you have, out of the wind.
A greenhouse lets you start earlier. A balcony does not, if nights still freeze: the pot gets as cold as the air.
Spacing and pots
In the ground the RHS spaces plants 45–60 cm (18–24 in) apart, depending on how big the variety gets. Check the packet. One plant fits a 30–45 cm (12–18 in) pot with drainage holes. Pot size and compost are in the container garden guide.
On tall, single-stem (cordon) varieties, pinch out the shoots that appear in the leaf joints. On bush varieties, leave those shoots. The method is in side shoots and pruning. Tall plants need a sturdy stake.
Water, neighbours and disease
Keep the soil evenly moist. Swings from wet to dry split the fruit and encourage blossom end rot. Water the soil in the morning, not the leaves: how much and how often is in the watering guide, and the hardware is in the drip irrigation guide. In pots, once the first fruits swell, the RHS suggests a high-potassium liquid feed every 10–14 days. In enriched ground you often need less.
Don't put tomatoes where tomatoes, potatoes, peppers or aubergines grew in the last few years. Late blight shows as brown blotches on leaves and fruit in cool, wet weather: what to do is in that guide, under pests and diseases. Basil and French marigold are the pairings people mention most: what is documented and what is tradition is in companion planting.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
Can I sow tomatoes in December or January?
Not in December: the seedlings sit in pots for months and grow leggy. In January, only in the south, or in the centre if the weather is already mild, and only with warmth and plenty of light. In the north, start in February.
Are sowing and planting the same job?
Sowing is the seed in a tray indoors. Planting, on this page, means setting the young plant in its final place, outside or in a large pot.
How far apart should the plants be?
The RHS says 45–60 cm (18–24 in). One plant fits a 30–45 cm (12–18 in) pot.
When do I plant tomatoes in a pot on a balcony?
On the same dates as planting in the ground, in full sun, in a 30–45 cm pot. If nights still freeze, keep the pot under cover.
Why do fruits split or rot at the tip?
Often from uneven watering. Keep the soil steadily moist and water the soil, not the leaves. Brown blotches that spread across leaves and fruit in cool, wet weather are a different problem: late blight.