Lemons are one of the least cold- and frost-tolerant species of citrus. Typically grown in frost-free climates, when an episode of unusually cold and or windy weather hits, lemon trees will need protection to prevent premature fruit drop, branch die back and defoliation. Lemon trees are in active growth nearly year round, so there is always young tender wood and either bud, blooms or fruit in some stage of development.
Provide consistent growing temperatures above a bare minimum of 30 degrees F to prevent bud and fruit loss. Exposure to temperatures just below this threshold can result in defoliation and wood die back.
Wrap the trunk of your lemon trees snugly up to the main branches with blankets, piles of palm fronds, foam sheets, carpet padding, carpet or other insulating material and secure with twine to completely encase the trunk but not cover the soil.
Protect trunk insulation in rainy or wet conditions by wrapping in plastic sheeting or tarps to prevent it from getting wet. Again wrap the trunk to the main branches but do not cover the surrounding bare soil which help to warm the tree. Use twine to secure snugly at several points on the trunk.
Wrap the trunks and large branches of your lemon trees in outdoor Christmas lights. Leave the lights on all night until past daybreak each night frost or low temperatures are threatened. Alternatively hang a 100-watt outdoor-approved bulb in the center of each lemon tree and leave it burning through the night.
Keep the soil around your lemon trees moist, as moist soil holds more heat than cold. If possible, leave the water on at night with a small trickle of running water or drip irrigation to give off heat and help to raise ambient temperatures and prevent frost damage.