- Keep off frozen or waterlogged soil and lawns.
- Winter-prune apples, pears and wisteria.
- Check stored dahlia tubers and bulbs for rot.
- Move pots of borderline plants against the house wall in cold snaps.
- Sow sweet peas, chillies and onions from seed under cover.
Spotlight: keeping potted plants alive through frost
A plant that is perfectly hardy in the ground can die in a pot, because roots in a container have no soil around them to buffer the cold. A rootball can freeze solid in a single hard night, and a frozen rootball can't take up water even when the sun comes out, so evergreens dry out and scorch.
Three things make the difference. First, drainage: raise pots on feet and never leave them in saucers over winter, because wet compost freezes harder and rots roots. Second, position: move pots together against the house wall, where they share warmth and are out of the wind; a porch or unheated garage works for the coldest spells. Third, insulation: wrap the pot, not only the plant, with hessian, bubble wrap or an old blanket, and cover the top growth with horticultural fleece on nights forecast below about -3°C. Take the fleece off in the day so the plant isn't sitting in damp.
Plants to worry about most are the Mediterranean ones people now grow on patios — olive, bay, citrus, oleander, callistemon — and anything rated H3 or lower. Terracotta also suffers: unless it is frost-proof, it can flake or crack once wet clay freezes.
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Protecting plants from frost and wet
Most hardy plants shrug off cold; what kills them is cold combined with wet roots, or a frozen pot. Terracotta and glazed pots crack and their rootballs freeze solid, which the plant can't survive even if it would be fine in the ground.
Winter pruning
Deciduous trees and shrubs are dormant, so you can see their structure and cut without losing flowers. Leave spring-flowering shrubs alone: forsythia, philadelphus and weigela are pruned after they flower.
Houseplants in winter
Low light and dry central heating are the two things that stress houseplants in January. Most need far less water than in summer: more houseplants die of overwatering in winter than of anything else.
Fruit and vegetables
Winter vegetables are still being picked, and fruit bushes can be planted and pruned. January is also seed-ordering month: a plan now saves wasted packets later.
Sow and plant
- Sweet peas in deep pots, under cover
- Chillies and sweet peppers with heat
- Onions from seed with gentle warmth
- Antirrhinums on the surface of compost, under cover
- Bare-root roses, trees and hedging when the soil isn't frozen
- Bare-root fruit bushes
- Amaryllis bulbs indoors
Watch out for
Questions
Can I plant in January?
Yes, bare-root trees, shrubs, roses and hedging can be planted whenever the soil is neither frozen nor waterlogged. Container plants can too, but they establish faster in autumn or spring.
Should I cut back frost-damaged plants?
Not yet. Damaged leaves and stems shelter the buds underneath from further frost. Wait until mid-spring, when new growth shows where the live wood starts.
Is it too early to sow seeds?
For most plants, yes: seedlings raised in poor January light get leggy. The exceptions are slow crops that need a long season — chillies, onions from seed, sweet peas and antirrhinums.