UK hardiness lookup
Truro (Cornwall) (TR1) — RHS hardiness H3
Truro (Cornwall), England · 230-day frost-free season
Frost dates and growing season for TR1
| RHS hardiness rating | H3 |
|---|---|
| Average last spring frost | late March |
| Average first autumn frost | mid-November |
| Growing season length | ~230 days |
| Temperature range (C) | minimum -5 to 1 °C |
| Temperature range (F) | minimum 23-34 °F |
| USDA equivalent | Roughly USDA zone 8b/9a. |
UK frost dates come from Met Office regional climate averages (1991-2020). Frost pockets, valleys, and exposed elevation can shift Truro (Cornwall)-area gardens a full band colder than the regional figure. Coastal and urban gardens run a band warmer.
What grows at RHS H3 in Truro (Cornwall)
Plants that tolerate a brief light frost but suffer when temperatures sit below freezing for more than a few hours.The RHS rates plants — not regions — so check the rating on each plant's tag against this H3 baseline. Anything rated H3 or hardier (numerically higher) should overwinter reliably in a typical Truro (Cornwall) year.
- Phormium tenax (New Zealand flax)
- Cordyline australis (mature plants)
- Olearia
- Hebe (taller varieties)
- Salvia greggii / microphylla
- Penstemon (most cultivars)
- Trachelospermum jasminoides
- Pittosporum tenuifolium
- Melianthus major
- Agave americana (in coastal Cornwall only)
When to plant in Truro (Cornwall)
Sowing, transplant, and harvest dates for the most common edible crops, calibrated to RHS H3 timing:
- When to plant tomatoes at RHS H3
- When to plant peppers at RHS H3
- When to plant basil at RHS H3
- When to plant garlic at RHS H3
- When to plant lettuce at RHS H3
- When to plant bush beans at RHS H3
- When to plant cucumbers at RHS H3
- When to plant summer squash at RHS H3
- When to plant peas at RHS H3
- When to plant carrots at RHS H3
For a one-shot starting point: tomatoes go outside from the late March window onwards; garlic goes in 4-6 weeks before mid-November; 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 H3 is Roughly USDA zone 8b/9a. — see the matching USDA Zone 9 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 TR1. 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)
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