London, United Kingdom · 51.51°
When to plant lemon balm in London
The London dates are calculated from the observed last spring frost — a 2016–2025 mean of 6 April — rather than from a latitude estimate or a national calendar. The frost-free season here averages 228 days.
Season anchorobserved 2016–2025
Last spring frost: 6 April · latest 30 Apr
First autumn frost: 20 November · earliest 1 Nov
Frost-free season: 228 days · 10 complete years
These come from the ERA5 reanalysis on a roughly 9 km grid, so they describe the area rather than your plot. A hollow, a frost pocket or an exposed site regularly runs several degrees colder, so use the cautious date for a decision you cannot undo.
Frost date estimator →Local calendar windows
The cautious column is calculated from the latest frost recorded in the period (30 Apr). Use it for tender crops you cannot re-sow.
The year in London
What can move the date
It self-seeds enthusiastically — cut the flowers off before they set unless you want it everywhere. Best in a pot or a corner where spreading does no harm.
Final spacing: 45 × 60 cm. Soil: pH 6–7.5.
Direct-sow only once the soil holds 12°C or more — soil temperature decides germination, not the date.
Problems in London
Each has its locally favourable conditions counted month by month, from the weather archive for this city.
Full guide: lemon balm diseases and pests →