Growing condition
Frost damage
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in January | Watch for in February | Watch for in March | Watch for in April | Watch for in May | Watch for in October | Watch for in November | Watch for in December |
What it is
Frost damage happens when ice forms in or around plant tissue and ruptures cells. In the UK it causes most trouble in two ways: sudden late spring frosts that catch new growth, blossom and freshly planted tender crops, and hard winter spells that hit borderline-hardy shrubs and plants in pots. Low-lying gardens and frost pockets suffer most.
Symptoms
The morning after a frost, soft shoots and leaves look limp and water-soaked, then turn black or brown within a day or two. Potato and dahlia foliage collapses; young Japanese maple and hydrangea leaves shrivel at the tips. Evergreens such as pittosporum and camellia may show browned, scorched leaves, often worst on the side facing the morning sun. Fruit blossom with a black centre will not set fruit. Bark can also split on young trees.
Cause
Clear, calm nights let heat escape quickly from the ground, and cold air drains downhill, collecting in hollows and against walls or hedges that block its path. Rapid thawing in early sun often worsens injury. Plants that have been grown soft under cover, or fed heavily late in the season, are far more vulnerable than hardened-off ones. Wet roots in winter make borderline plants more likely to die.
Control
Resist the urge to cut off damaged growth immediately, because it shelters the buds below from further cold. Once the risk of frost has passed, usually by late May in the south and later further north, trim back to healthy buds and give a light feed. Most hardy shrubs reshoot. Tender bedding and vegetables killed outright will need replacing; potatoes usually regrow from below ground.
Prevention
Check the forecast in spring and throw horticultural fleece over tender crops and blossom on clear nights. Harden off plants for a week or two before planting out. Site tender shrubs in sheltered spots away from frost pockets and early morning sun, move pots against the house or into a cold greenhouse in winter, and mulch the crowns of dahlias, agapanthus and fuchsias.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: January, February, March, April, May, October, November and December.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.