Hardy vs Tender Plants — What's the Difference?

Every plant label and catalogue description you read will include some reference to hardiness — "fully hardy", "half-hardy", "frost-tender" — but what do these terms actually mean, and how do they determine what you need to do in your garden when cold weather arrives?

Fully hardy

A fully hardy plant survives outdoors year-round in temperate climates without any protection. In the UK, this generally means surviving down to around -15°C. Examples include most deciduous trees and shrubs, hardy perennials, biennials like foxgloves, and cool-season vegetables like kale, sprouts, and parsnips. These plants can be left in the ground through winter with no intervention at all. Fully hardy plants from colder climates like Scandinavia or Russia are sometimes described as "extremely hardy" and may survive temperatures far below -15°C.

Half-hardy

Half-hardy plants survive light frosts (down to around -5°C) but are damaged or killed by prolonged hard freezing. Many popular garden plants fall into this category — Japanese maples, many ornamental grasses, some hydrangeas, fig trees, and Mediterranean herbs like rosemary and lavender in poorly drained soils. Half-hardy plants often need protection in cold, exposed gardens but survive without help in sheltered urban settings. A south-facing wall or microclimate can push a half-hardy plant into effectively hardy behaviour in practice.

• Fully hardy: tolerates -15°C and below, no protection needed.
• Half-hardy: tolerates light frosts, needs shelter in exposed sites.
• Frost-tender: damaged or killed below 0°C, must be protected or overwintered.
• Half-hardy annual: survives mild frost as a mature plant but killed as a seedling.

Frost-tender and tropical plants

Frost-tender plants are damaged or killed by any freezing temperature. This includes most bedding plants (pelargoniums, begonias, impatiens), tender perennials used as summer bedding, and most tropical or subtropical plants. These must be brought indoors before the first autumn frost or treated as annuals and replaced every year. The boundary between "tender" and "half-hardy" is not always clear — some plants marketed as frost-tender in cold northern areas are perfectly hardy in milder southern or coastal regions.

Hardiness in practice

Official hardiness ratings are guidelines, not guarantees. Your specific garden microclimate — aspect, shelter, soil drainage, proximity to buildings or walls — can shift a plant's effective hardiness by one or two categories. A plant rated half-hardy may survive for years in your sheltered walled garden while dying in your neighbour's exposed garden. Soil drainage is particularly important — many plants that would survive cold die in wet, cold soil because waterlogging damages roots while they are dormant.