Orange trees (Citrus sinensis) are relatively hardy trees grown throughout their suitable planting regions of USDA planting zones 9 through 11. They prefer a frost-free climate, as all varieties are frost sensitive and can be damaged if grown in areas experiencing prolonged and annual frosts and freezes. All varieties are evergreens and do not have a complete dormancy stage, making them more susceptible to damage in freezes or frosts. Since the extent of freeze damage can takes months or years to show, gardeners can do no more than wait to see if their orange trees are dead.
Delay trimming any damaged branches until the later part of spring or summer, as new growth can sprout from what seems like dead sections. Pruning too soon can lead to trimming off branches that are alive, and new growth will suffer damage in the event of more frosty weather.
Inspect the orange tree's bark and larger branches for splitting or loosening, after warm weather returns. Severely freeze-damaged trees will have the outer layer of bark separate from the trunk and branches, and that section of the tree will die. It can take up to two years for freeze-damaged areas of the orange tree to die completely.
Check the orange tree's foliage for damage, once springtime temperatures arrive in your area. Freeze-damaged orange tree leaves that are dead turn hard and become brittle. Cold weather naturally causes the foliage to have a wilted look, but does not cause it to harden or become brittle, resulting in leaf drop and indicating possible death of that section of the tree.
Prune away any damaged or dead areas of the orange tree only when warm weather is consistent in your region. Use sterilized pruning tools wiped with alcohol, so you do not transfer diseases or bacteria to the tree through the fresh cuts.
Delay watering immediately after the orange tree suffers through a frost or freeze to keep the tree in a dormant stage. Withholding water delays new growth from forming and protects the tree from further damage. Water the tree only when new growth resumes.
Fertilize the freeze-damaged tree only when new growth resumes in springtime to help revitalize the orange tree. Apply at half the specified rate, if half the tree is dead due to the freeze. Use a citrus blend applied under the orange tree's canopy and away from the trunk, watering in well after applying.
Wait to see if the orange tree continues producing new growth after warm weather returns, the watering schedule is resumed and applying fertilizer. If the tree remains free of leaves or new growth drops from the tree, branches turn brown or black showing death, the orange tree is dead. Dig the tree from the area and replace with a new one.