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Frost Damage

Plant disorder

Description​

Frost damage is an injury caused when plant tissues become cold enough for ice to form or for cells to lose water to ice forming around them. It is an environmental disorder, not a disease, and it has no scientific name. Tender plants may be damaged by a single cold night, while established hardy plants usually tolerate much lower temperatures. Leaves and flowers are often affected first because they are exposed and poorly insulated. After thawing, injured tissue may look water-soaked, limp or translucent, then turn brown or black and dry out. New shoots can die back, young seedlings may collapse, and fruit can develop soft or discolored patches. Damage varies with the plant’s hardiness, its stage of growth, how quickly temperatures fall, and how long the cold lasts. Frost near the ground may harm low-growing plants while leaving foliage higher up relatively untouched.

Symptoms​

  • Brown or crispy leaf edges
  • Wilting
  • Bleached or scorched patches
  • Leaves dropping
  • Flowers or buds dropping
  • Seedlings collapse at soil level
  • Stunted growth

How to Identify​

Check whether symptoms appeared suddenly after a night near or below freezing. Frost-injured leaves often wilt as they thaw, then become water-soaked, dark, papery or scorched. Flowers may blacken and drop, and tender shoots can die back. Damage is often worst on exposed growth, in low spots where cold air settles, or on plants left uncovered. Unlike a spreading infection, the affected area generally reflects which tissues experienced the cold; new damage does not continue once temperatures recover. Drought can also cause wilting, but its leaves usually do not first appear water-soaked after a cold night. Sunscald is more concentrated on sun-exposed surfaces.

Prevention​

Choose plants suited to your local climate and put frost-tender crops outdoors only after the usual last-frost date, while continuing to watch forecasts. Harden off indoor-grown seedlings gradually. Before a forecast frost, move containers under shelter or indoors. Cover in-ground plants with frost cloth or a sheet supported above the foliage, and secure its edges to the ground to retain warmth; remove the cover when temperatures rise. Avoid letting plastic rest directly on leaves. A layer of mulch helps insulate roots, especially on perennials. If the soil is dry, water it during the day before the cold night, but do not waterlog it. Avoid late-season nitrogen feeding or heavy pruning that encourages vulnerable new growth.

Treatment​

Once a plant has thawed, leave damaged leaves in place initially and give it time to show which stems and buds are still alive. Do not rub or handle frozen foliage: it breaks easily. Protect the plant from further cold nights with a suitable cover, and keep the soil moderately moist without overwatering; damaged plants often use less water. Remove soft, rotting fruit and any mushy tissue that threatens healthy growth. After the risk of frost has passed and new growth begins, prune dead shoots back to living tissue using clean tools. For woody plants, wait until spring growth makes the extent of dieback clear. Severely damaged annual seedlings may need replacing. Dead tissue will not turn green again, but healthy roots or buds may produce new growth. Fertilizer and pesticides do not repair frost injury; avoid applying them unless a separate, identified problem calls for treatment.

Plants Affected​

African Mahogany, Aloe Vera, Arborio Rice, Arrowroot, Australian Sandalwood, Banana, Baobab, Basil, Bay Leaf, Blue Gum, Bluebeard, Blueberry, Buckwheat, Caryopteris, Ceylon Ebony, Cherry Blossom, Choisya, Cistus, Coconut Palm, Cork Monkey Puzzle, Cork Oak, Corylopsis, Curry Leaf, Date Palm, Drumstick, Ebony, Echeveria, Escallonia, Eucalyptus, Fig, Fonio, Forbidden Rice, Gaboon Ebony, Galangal, Garrya, Ghost Orchid, Ginger, Glutinous Rice, Griselinia, Hebe, Heliconia, Honduran Mahogany, Hydrangea, Jacaranda, Jack Bean, Jade Vine, Japanese Maple, Japonica Rice, Jicama, Kaffir Lime Leaf, Lemongrass, Lotus, Magnolia, Mahogany, Malanga, Mango, Marjoram, Monkey Puzzle, Myrtle, Nasturtium, Oil Palm, Paeonia, Peach, Pineapple, Plantain, Purslane, Queen Palm, River Red Gum, Rockrose, Rosemary, Royal Palm, Sacred Fig, Sago Palm, Sandalwood, Santolina, Saucer Magnolia, Scarlet Runner Bean, Sequoia, Star Magnolia, Sweet Potato, Swietenia, Tamarind, Taro, Tasmanian Blue Gum, Teak, Teff, Tepary Bean, Teucrium, Vitex, Walnut, Water Hyacinth, Water Lily, Windmill Palm, Yellow Rice

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