UK hardiness lookup
London (Hampstead) (NW3) — RHS hardiness H4
London (Hampstead), England · 193-day frost-free season
Frost dates and growing season for NW3
| RHS hardiness rating | H4 |
|---|---|
| Average last spring frost | mid-April |
| Average first autumn frost | late October |
| Growing season length | ~193 days |
| Temperature range (C) | minimum -10 to -5 °C |
| Temperature range (F) | minimum 14-23 °F |
| USDA equivalent | Roughly USDA zone 8a/8b. |
UK frost dates come from Met Office regional climate averages (1991-2020). Frost pockets, valleys, and exposed elevation can shift London (Hampstead)-area gardens a full band colder than the regional figure. Coastal and urban gardens run a band warmer.
What grows at RHS H4 in London (Hampstead)
The default rating for "British garden hardy". Plants in this band cope with most UK winters but can be damaged in unusually cold years.The RHS rates plants — not regions — so check the rating on each plant's tag against this H4 baseline. Anything rated H4 or hardier (numerically higher) should overwinter reliably in a typical London (Hampstead) year.
- Buddleja davidii
- Lavandula angustifolia
- Rosa (most modern shrub and floribunda roses)
- Sarcococca (sweet box)
- Camellia japonica
- Choisya ternata
- Ceanothus (most cultivars)
- Hydrangea macrophylla
- Wisteria
- Magnolia (M. grandiflora, M. soulangeana)
When to plant in London (Hampstead)
Sowing, transplant, and harvest dates for the most common edible crops, calibrated to RHS H4 timing:
- When to plant tomatoes at RHS H4
- When to plant peppers at RHS H4
- When to plant basil at RHS H4
- When to plant garlic at RHS H4
- When to plant lettuce at RHS H4
- When to plant bush beans at RHS H4
- When to plant cucumbers at RHS H4
- When to plant summer squash at RHS H4
- When to plant peas at RHS H4
- When to plant carrots at RHS H4
For a one-shot starting point: tomatoes go outside from the mid-April window onwards; garlic goes in 4-6 weeks before late October; brassicas and salads can run on either side of the frost window with fleece in cold snaps.
Local microclimate notes
Postcode-area ratings are a baseline — your actual garden can sit a band warmer or colder. Urban heat-island effect lifts inner-city gardens; frost pockets at the bottom of slopes drop them. If you can record your own lowest winter temperature for a couple of seasons, that beats any regional average for planning.
For US gardeners reading UK references: RHS H4 is Roughly USDA zone 8a/8b. — see the matching USDA Zone 8 guide for the US-side planting calendar.
Source and methodology
Hardiness rating from the Royal Horticultural Society hardiness rating scale. Frost-date averages from Met Office UK climate averages (1991-2020), matched to the nearest representative regional station for postcode NW3. Plant recommendations curated by the Growli editorial team. Last review 2026-05-19.
Other postcode areas in England
- EC1 — London (Clerkenwell) (RHS H4)
- EC2 — London (City) (RHS H4)
- WC1 — London (Bloomsbury) (RHS H4)
- WC2 — London (Covent Garden) (RHS H4)
- W1 — London (Mayfair / Soho) (RHS H4)
- SW1 — London (Westminster / Belgravia) (RHS H4)
- NW1 — London (Camden) (RHS H4)
- N1 — London (Islington) (RHS H4)
- E1 — London (Whitechapel) (RHS H4)
- SE1 — London (Southwark) (RHS H4)
- SE10 — London (Greenwich) (RHS H4)
- SW19 — London (Wimbledon) (RHS H4)
- Browse all UK postcode areas