GardenCalc
Updated August 2026. Reference point: postcode district SW1A, Greater London (Westminster reference point). Your own postcode may differ by a week or two, so check your exact frost dates.
London frost dates at a glance
Sowing and planting-out windows for London, 2026
Every date below is worked out from London's safe last-frost date (14 Apr) using RHS and Thompson & Morgan sowing offsets. Windows are for outdoor-grown plants; greenhouse crops start earlier.
| Crop | Sow indoors | Sow direct outside | Plant out |
|---|---|---|---|
| Tomatoes tender | 17 Feb to 3 Mar | – | 14 Apr to 28 Apr |
| Potatoes tender | – | 24 Feb to 31 Mar | 24 Feb to 31 Mar |
| Runner beans tender | 3 Mar to 24 Mar | 14 Apr to 26 May | 14 Apr to 28 Apr |
| Sweet peas hardy | 1 Feb to 3 Mar (held to February, the earliest in the cited guidance) | 3 Mar to 14 Apr | 3 Mar to 14 Apr |
| Dahlias tender | 1 Feb to 3 Mar (held to February, the earliest in the cited guidance) | 17 Mar to 31 Mar | 14 Apr to 28 Apr |
| Courgettes tender | 3 Mar to 24 Mar | 14 Apr to 12 May | 21 Apr to 5 May |
| Cucumbers (outdoor) tender | 10 Mar to 24 Mar | 21 Apr to 12 May | 21 Apr to 5 May |
| Sunflowers half-hardy | 17 Feb to 17 Mar | 17 Mar to 28 Apr | 14 Apr to 28 Apr |
| Pumpkins and winter squash tender | 3 Mar to 24 Mar | 14 Apr to 12 May | 14 Apr to 5 May |
| Sweetcorn tender | 3 Mar to 17 Mar | 14 Apr to 5 May | 14 Apr to 5 May |
| French beans tender | 10 Mar to 31 Mar | 14 Apr to 2 Jun | 14 Apr to 28 Apr |
| Chillies tender | 1 Feb to 17 Feb (held to February, the earliest in the cited guidance) | – | 21 Apr to 12 May |
| Sweet peppers tender | 3 Feb to 24 Feb | – | 21 Apr to 12 May |
| Basil tender | 17 Feb to 31 Mar | 28 Apr to 26 May | 21 Apr to 12 May |
| Geraniums and tender bedding half-hardy | – | – | 14 Apr to 28 Apr |
Get windows for your own postcode → Full UK planting calendar →
Before the first frost in London (typically 21 Nov)
- Tomatoes: Pick all remaining fruit before the first frost and ripen it indoors, or lift whole plants and hang them under cover. Source
- Potatoes: Lift maincrop potatoes on a dry day before the first hard frost; frosted tubers rot in store. Source
- Runner beans: Pick the last pods before the first frost, then cut plants down to the base and leave the nitrogen-rich roots in the soil. Source
- Sweet peas: Hardy, so no rescue needed; pull up finished plants in autumn, and overwinter any autumn-sown seedlings in a cold frame. Source
- Dahlias: The first frost blackens the foliage; cut stems down, then lift and store the tubers somewhere frost free, or mulch deeply and leave them in the ground in mild areas. Source
- Courgettes: Pick all remaining fruit before the first frost, which kills the plants outright. Source
- Cucumbers (outdoor): Harvest the remaining fruit before the first frost; outdoor plants collapse in the first freeze. Source
- Sunflowers: Plants die back with the first frosts; leave the seedheads standing for the birds, or cut and dry them first if you want the seed. Source
- Pumpkins and winter squash: Harvest and cure the fruits before the first frost; frosted pumpkins cannot be stored. Source
- Sweetcorn: Pick any remaining cobs before the first frost, which ends the crop. Source
- French beans: Pick the last beans before the first frost; even a light frost kills the plants. Source
- Chillies: Bring plants under cover, or pick every remaining fruit, before the first frost; chillies will not survive it outside. Source
- Sweet peppers: Pick the remaining fruit, and fleece outdoor plants or bring potted ones under cover, before the first frost. Source
- Basil: Bring pots indoors or pick the remaining leaves before the first frost; one cold night finishes basil outdoors. Source
- Geraniums and tender bedding: Bring containers under cover, and lift and pot up bedded plants, before the first frost; or take cuttings in late summer and treat the parents as annuals. Source
Is there a frost risk tonight? Live forecast → Farm shops near London →
Ground frost days by month, London
Average number of days with a ground frost each month, 1991 to 2020 (observed, Met Office).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 14 | 11 | 6 | 2 | 0 | 0 | 0 | 0 | 3 | 8 | 14 |
London frost and sowing questions
When is the last frost in London?
In London the last air frost is typically around 7 Mar, and it is safe (9 years in 10) from about 14 Apr. The latest recorded in the 30-year record was 21 Apr. Based on Met Office HadUK-Grid 5 km data, 1991 to 2020, for postcode district SW1A.
When is the first frost in London?
The first autumn air frost in London typically arrives around 21 Nov. It has come as early as 18 Oct in the 30-year record.
How many frost-free days does London get?
About 259 frost-free days a year, between the typical last spring frost and the typical first autumn frost.
When can I plant out tomatoes in London?
After the safe last-frost date, so from about 14 Apr in London, and within the first two weeks after it. Sow them indoors 6 to 8 weeks before that.
Where these dates come from
Frost dates: Met Office HadUK-Grid 5 km gridded daily minimum temperature, 1991 to 2020, air frost at 0°C, for postcode district SW1A (Contains public sector information licensed under the Open Government Licence v3.0). "Safe" means 9 years in 10 the last frost had already passed by that date. Limits: a 5 km grid smooths frost hollows, valley bottoms and urban heat islands, so a sheltered city garden or an exposed edge-of-town plot can differ. Sowing offsets: RHS and Thompson & Morgan grow guides, linked per crop above. This page is not a forecast; use the live forecast for tonight.
Frost warnings and sowing reminders for London
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