Which Plants to Bring Inside Before Frost

Every autumn the same question arises: which tender plants are worth the effort of overwintering indoors, and when do they need to come in? Getting the timing and conditions right determines whether your saved plants thrive to flower again next year or slowly deteriorate over winter.

Plants worth overwintering indoors

Pelargoniums (tender geraniums) are the classic candidate — a well-grown plant is expensive to replace and overwinters easily in a cool, bright frost-free space. Fuchsias, cannas, dahlias, and begonias can all be overwintered as dormant tubers or lifted roots in a frost-free garage or shed. Tender perennials like osteospermum, argyranthemum, and Diascia overwinter well as rooted cuttings or entire plants in a cool greenhouse or porch. Citrus and tender container shrubs need frost-free conditions and as much light as possible.

When to bring plants inside

Monitor forecasts from late September onwards. Bring tender plants inside before the first forecast frost — not after. A single hard frost can kill pelargoniums, fuchsias, and begonias outright, even if the plants looked healthy moments before. As a general rule, start the process of moving plants under cover when overnight temperatures consistently drop below 5°C, regardless of whether a frost has been formally forecast.

• Start monitoring forecasts from mid-September.
• Bring in before the first frost, not after.
• Move when overnight temperatures regularly drop below 5°C.
• Reduce watering and feeding a few weeks before moving.

Conditions needed indoors

Most overwintering tender plants need a frost-free, cool, and reasonably bright location. A cool greenhouse, unheated conservatory, or frost-free garage with a window is ideal. Actively warm, centrally heated rooms are too warm and dry for most plants — they don't rest properly and exhaust themselves growing leggy in low light. Aim for 5–10°C and the brightest available natural light. Reduce watering significantly during winter dormancy to avoid root rot in the reduced light levels.

Preparing plants before moving

Before bringing plants inside, reduce their size. Cut pelargoniums back by a third, remove all dead and diseased material, and inspect for pests — particularly vine weevil grubs in the compost, and aphids and whitefly on the foliage. Bringing pests indoors gives them free rein over winter. Treat any infestations before moving the plant. Remove all dead flowers and leaves to reduce the risk of botrytis (grey mould) developing in the lower-light, lower-airflow conditions indoors.