Freeze is a word that often strikes fear in the heart of all of those who own citrus trees. Whenever the temperature dips below 32 degrees, the possibility of damage to citrus trees becomes very real. While nearly all citrus trees can deal with below freezing temperatures for a few hours, the extent of the damage will often depend on how cold it gets and how long it stays below freezing, along with the tree's overall health before the freeze.
Not all species of citrus trees are affected by the same temperature extremes. For example, some varieties of orange trees can survive quite well at temperatures as low as the mid 20s for a few hours. Lemon trees, on the other hand, are often very susceptible to cold weather and will need some protection should the temperature approach 32 degrees, or the entire tree could die. The longer the temperature stays below the freezing mark, the greater the likelihood there will be tissue damage.
One of the best ways to prevent citrus trees from freezing is to make sure you live in a location where they can be planted and cared for effectively. Nearly every location in the United States, except for extreme southern Florida and southern coastal California, will likely experience freezing temperatures at least once every few years. Citrus trees in other locations will require special precautions or protection.
Locating your tree on the south facing side of a home or building, but relatively close to that building, is helpful in preventing the effects of cold temperatures. This location gives the tree the full benefit of the winter sun and provides some radiant heat from the building. If temperatures dip too low, covering a small tree with a blanket and using an incandescent light in a portable fixture could provide extra warmth on cold nights.
Though it may seem counter-intuitive, water is often used to protect citrus trees when a freeze is expected to occur. First, the ground is often saturated with water the day before a freeze is to take place. This stops the ground from changing temperature as rapidly as the air. Water may also be applied to a tree during a freeze, as the freezing process naturally draws heat and the water provides a degree of insulation from colder air temperatures.
It should be noted that water, while it is often used, may not be enough to save a tree from a severe freeze. If temperatures remain too cold for too long, even the insulating power of the water will be ineffective. Likewise, using water during a prolonged freeze could cause ice buildup on the limbs, the weight of which could cause them to break off.