Killer cold can strike your garden at any time now through March. Sacramento’s average annual first frost date is Nov. 14, and last week’s lows flirted with freezing.
Here are some reminders for coping with frosty nights:
▪ If temperatures below 32 degrees are forecast, water your plants lightly in the late afternoon or early evening before frost hits. Wet soil holds more heat than dry soil and this also raises the humidity level. Well-hydrated plants can cope better with frost “burn,” which results from moisture being pulled out of the foliage to protect the main trunk and roots.
▪ Pull back mulch away from plants so the ground can radiate any stored heat.
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▪ If overnight frost is expected, move potted plants to protected areas indoors or under the shelter of a covered patio.
▪ Cover sensitive plants before sunset; that helps capture any ground heat and keeps it close to the plants. Cloth sheets or blankets work better than clear plastic and can increase the temperature 5 degrees. Allow a little room for air circulation under the cover; that helps keep in warmth, too. Remember to Remove the covers by mid-morning or risk suffocating the plant.
▪ Use heat caps or row covers to protect tender vegetable transplants.
▪ Plants in raised beds or on mounds stay warmer than those planted in sunken areas, where cold air collects.
▪ String old-fashioned Christmas lights – the ones that get hot – on the trunks and limbs of citrus, avocado and other frost-sensitive trees and bushes. The big lights give out more heat than mini-lights. LEDs offer no heat for plant protection.
▪ Wrap the trunks of tender trees or shrubs with rags, towels, blankets or pipe insulation.
▪ If temperatures are expected to go below 30 degrees, harvest ripe citrus fruit to avoid potential damage.
▪ If a plant shows frost burn, don’t cut off the damaged foliage. It will help protect the plant from further harm. Remove the burned leaves in spring.