H3 - Half-hardy

Plants that can survive light frost and sheltered winters, yet remain vulnerable during prolonged freezing weather or in exposed, colder British gardens.

What it means

H3 plants are half-hardy, tolerating roughly -5 to 1 degrees C. They can often remain outside in mild coastal or urban gardens, where winters may be around H3, especially beside a warm wall or in free-draining soil. Elsewhere they need a protected microclimate or winter cover. Cold inland, upland and Scottish gardens are less reliable for them. The rating concerns the plant itself, not geography.

Example plants

H3 examples include many shrubby salvias, some tender hebes, hardy-looking but variable fuchsias, olives in mild districts and exotic foliage plants such as tetrapanax. Mediterranean shrubs and evergreen perennials are common choices at this level. Their performance depends greatly on drainage, wind exposure, maturity and winter wet, so one cultivar may prove tougher than another in the same garden.

Protecting these plants

Choose a sunny, sheltered site, ideally near a wall, with soil that drains freely in winter. Mulch roots after the ground cools and use horticultural fleece during sharper frosts, removing it in mild weather. Keep container plants close to the house or under cover. Young plants need extra attention; move them to shelter or replace them after unusually severe winters.

RHS hardiness ratings describe a plant's cold tolerance, not a geographic zone. Local conditions vary; the RHS or a local garden centre can advise. Page updated 18 Sep 2026.