Q. When should I begin to protect plants like citrus from the freezing weather that’s coming?
A. Some citrus will handle the cold weather better than others. Most of the citrus sold in this area are grafted to a cold hardy root system called a rootstock. Damage or even death results when the temperatures remain low enough to kill the top of the tree, its root system or both.
|This citrus died from winter freezing temperatures several years ago and the sour orange rootstock grew in its place producing oranges that were too sour to eat.|
The more cold hardy and reliable citrus here are kumquat, grapefruit and Myers lemon. However, they will not survive the cold if the roots which they are grafted to are not cold tolerant as well. Most plants sold by nurseries in this area have citrus on cold hardy rootstock. This might not be the case if you buy citrus online.
|Spring freezing weather caused this fig to die back and push new growth from lateral buds along the stem.|
None of the citrus are severely damaged if temperatures remain above 32° F. The least cold tolerant of the citrus, such as limes, is damaged when temperatures drop below freezing. When temperatures are low enough to damage the top of the tree but not the rootstock, suckers or water sprouts grow from the rootstock the following spring while the top of the tree may be dead or severely damaged.
|Freeze damage to bougainvillea|
As we start getting close to 32F, start watching the local weather reports or track the low temperatures online. When you see projected temperatures reaching 32° F or lower, wrap the base of the tree with a blanket or cover this area with mulch. Smaller trees or trees pruned into an espalier may be entirely covered with a blanket.
Some people wrap tender trees with Christmas lights on a timer that comes on at night. This may work if temperatures are not extremely low and there is no wind. Blankets should be removed the next day when temperatures climb above freezing.