Orange trees (Citrus sinensis) are subtropical plants that prefer living in warm, humid climates. Sensitive to freezing temperatures, these trees suffer damage when temperatures drop to 28 degrees Fahrenheit or below for longer than four hours. The longer the temperatures remain freezing, the more damage occurs to the tree's leaves and branches. Older orange trees are more hardened to cold weather than young saplings. If you live in an area that experiences annual freezes or an occasional freeze, your orange tree will require protection.
Bring container-grown orange trees indoors to a warm location---if you can move the container. If your containers are too large to move indoors, bunch them together with other plants to help retain heat. Thoroughly water the soil and the orange tree's foliage, then cover the tree with a blanket before the freezing temperatures arrive.
Plant the orange tree in a warm location in your landscape. Planting the tree in a south to southeast location assures it will receive the most warmth and be protected from cold northern winds.
Plant the orange tree in a higher elevated location in your yard and not in a depressed area. Cold air lingers in lower locations, and you tree will suffer less exposure from the freezing temperature if planted in a higher area.
Water the soil around the orange tree thoroughly before the freezing temperatures arrive. Spray all the foliage with water so the leaves are moist when cold weather strikes. The water will help insulate the leaves and roots, helping retain heat.
Place a jet sprinkler upwind and approximately 3 feet from the tree, and turn it on during freezing temperatures. Allow the water to spray on the bottom third of the tree. This will help the tree's trunk and root system retain moisture, which will insulate the tree with heat protecting the graft. If placed downwind, the sprinkler's water will blow away from the tree without hitting it.
Cover the orange tree with a cloth blanket, burlap or sheet if it is not too large. Allow the covering to reach to the ground covering the tree's trunk. You can tie the covering in place with ropes.
Place an outdoor 60-watt light underneath the coverings to help create much-needed heat, or hang a holiday light set around the tree's canopy and trunk. Allow the lights to burn during the freezing temperatures, as they will create heat and protect the tree.