Growing Conditions · England
Test Valley Growing Conditions
Soil, hardiness and a planting calendar for Test Valley — across 5 postcode districts.
Soil
A shallow, free-draining alkaline soil over chalk or limestone. It suits chalk-loving plants and many herbs but locks up iron, so acid-lovers such as rhododendrons and blueberries struggle without raised beds of ericaceous soil. The thin topsoil dries fast — mulch to hold moisture. Expect rock close to the surface when digging footings.
Winter hardiness
Rated RHS H4 — the UK mainstream, with winter lows near -6°C. The vast majority of garden plants, perennials, shrubs and trees come through a normal winter unprotected; only genuinely tender exotics need a warm corner or cover.
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 typical UK growing season (~333 frost-free days), with the last frosts clearing through spring and first frosts returning in autumn.
Planting Calendar for Test Valley
Timings are guided by this area's ~333 frost-free days and RHS H4 hardiness; adjust for a cold or sheltered garden.
Conditions by Postcode
| Postcode | Soil | Hardiness | Rainfall |
|---|---|---|---|
| SO20 | thin, alkaline soil over chalk | RHS H3 | 817mm |
| SO52 | very acid, free-draining sandy loam | RHS H3 | 817mm |
| SP10 | free-draining acid loam — the classic 'good garden soil' | RHS H4 | 776mm |
| SP4 | fertile floodplain soil with a high water table | RHS H4 | 837mm |
| SP9 | free-draining alkaline loam | RHS H4 | 837mm |
