H2 - Tender

Frost-sensitive plants able to tolerate a cool, frost-free winter, usually in an unheated greenhouse or a protected indoor place.

What it means

H2 plants tolerate cool conditions down to about 1 to 5 degrees C but should not face frost. An unheated greenhouse, cold frame with added protection, porch or sheltered conservatory can provide suitable winter cover. They are useful outdoors during summer across the UK, but must be brought in or protected before freezing weather. This is a plant hardiness rating, rather than a map of British or overseas gardening areas.

Example plants

Typical H2 plants include pelargoniums, aeoniums, tender agapanthus, many succulents and some tender perennial salvias. Citrus and young olive trees may need similar protection in colder gardens, although their exact requirements vary. These plants are often grown in pots for easy movement, offering flowers or architectural foliage through summer without committing them to winter exposure in the border.

Protecting these plants

Keep H2 plants dryish and frost-free over winter, particularly succulents, which suffer if roots remain cold and wet. Move pots beneath cover before forecasts approach freezing. Ventilate glasshouses on mild days to reduce damp and mould, but close them before cold nights. In mild coastal gardens, temporary fleece may help during a brief cold snap, though dependable protection still means frost-free shelter.

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 19 Sep 2026.