Cold Hardiness

• Some types of citrus are more cold hardy than others (meaning they can survive colder temperatures without substantial damage), so selecting the type of citrus you grow is the first step to making sure your citrus trees survive cold temperatures. Oranges, grapefruits and mandarins that ripen fully on the tree can survive colder temperatures than lemons and oranges that partially ripen off the tree. Within each citrus, there are varieties that are more resistant to cold than others. Trifoliate orange, for example, is more cold hardy than sour orange.
  
  

Planting Stock Selection

• According to Texas A&M University's guide to cultivating citrus at home, seedling trees are more cold hardy than budded trees. Therefore, selecting citrus species as seedlings rather than budded trees from a nursery is an important way of ensuring that your citrus trees survive cold temperatures. Note, however, that seedling trees lose some of their cold tolerance when they are budded, so if you plan to propagate your citrus trees by budding, future generations will not be as cold tolerant as the original seedling tree.
  
  

Winter Protection

• Even when planting cold tolerant species and citrus varieties, you will more than likely need to protect the citrus trees from cold temperatures. Trunk wraps work well but provide only a few degrees of protection. A preferred method is a soil bank, a method whereby soil is piled around the tree trunk up to the tree's lowest vegetation. This method protects the tree from cold for the first two to four winters after being established, but should be avoided once the tree has been established in soil for more than four years.
  
  

Signs of Frost Damage

• Frost damage causes symptoms that mirror those of many other plant ailments, so it is important to recognize the signs to properly distinguish it from other conditions. Leaves or twigs will first appear water soaked and later will wither and turn brown or black. Tree death can occur in sensitive young trees or regrafted trees, but most mature trees will survive frost damage. If your citrus tree suffers from frost damage, allow it to outgrow the damage and protect it from cold temperatures in the future to avoid further damage.