Growing Conditions · England
Portsmouth Growing Conditions
Soil, hardiness and a planting calendar for Portsmouth — across 5 postcode districts.
Soil
A fertile coastal-flat soil with a high water table and, near the sea, some salt influence. Growth is strong in summer but winter-wet; choose salt- and wind-tolerant planting near the coast and raise beds for vegetables. Drainage, and salt-resistant materials, matter for any hardscaping.
Winter hardiness
A mild area rated RHS H3 — winters usually bottom out around -5°C. Most hardy plants are safe, and you can grow half-hardy exotics that fail further north, but the occasional hard frost means tender plants still want a sheltered wall or winter fleece.
Rain & growing season
Moderate rainfall (817mm a year) — enough for most gardens without heavy irrigation, though pots and new plantings need watering in summer. A long growing season (~341 frost-free days) — you can sow earlier and harvest later than most of the country, and squeeze in a second late sowing.
Planting Calendar for Portsmouth
The long season allows a second sowing of quick crops in July.
Timings are guided by this area's ~341 frost-free days and RHS H3 hardiness; adjust for a cold or sheltered garden.
Conditions by Postcode
| Postcode | Soil | Hardiness | Rainfall |
|---|---|---|---|
| PO1 | thin, alkaline soil over chalk | RHS H3 | 817mm |
| PO2 | loamy-clay with impeded drainage | RHS H3 | 817mm |
| PO3 | coastal flat soil, high water table, some salt | RHS H3 | 817mm |
| PO4 | heavy, base-rich clay loam that sits wet in winter | RHS H3 | 817mm |
| PO5 | coastal flat soil, high water table, some salt | RHS H3 | 817mm |
Planning work in Portsmouth?
Browse Companies House-registered landscaping businesses in the area.
