Protecting orange trees from winter weather is one of the most important parts of orange tree care. Citrus trees are generally intolerant of cold weather and a harsh freeze or frost can be fatal. However, with a little bit of easy-to-follow knowledge, you can be certain your orange tree will produce a healthy crop of fruit next season.
Know Your Variety
Study your variety of orange tree. Some varieties are more cold hardy and can survive even in below-freezing temperatures, while others need moderate or warm temperatures all winter long. Varieties that bear fruit early in the season are better choices for cooler climates. Remember: orange trees are tropical trees. They like warm and humid weather.
Orange trees grown in warm climates that stay above freezing for the entire winter will be fine with minimal care. Occasional frosts have been known to occur in even the warmest climates, however, so check overnight temperatures frequently and cover the trees in heavy blankets when the temperature is forecast to drop below 32 degrees.
Occasional Frosts and Freezes
Frosts are short periods of time -- a few hours usually -- when the temperature drops below 32 degrees. Cover the orange tree in heavy blankets during these periods. Freezes last longer and are much more serious when it comes to the health of your orange tree. While blankets can work, you may need additional heat sources. Large lights or lamps work for small or medium trees, while larger trees will need a heater.
Cooler and Cold Climates
Aside from a few hardy varieties, orange trees grown in colder temperatures will need to be brought indoors for the winter. Make sure the tree is in a large pot with plenty of room to grow. The pot should have lots of drainage. Before bringing it in, let it acclimate to warmer temperatures and lower levels of sunlight for two to three weeks by placing it in a shed or garage. This will also allow bugs to leave the tree. When you are ready, bring the tree inside and place it in a sunny location. Orange trees need plenty of sun, so a greenhouse, sun room or bright window is the best location for the tree. Mist the tree occasionally, particularly as houses can become very dry during the winter. Water when the top of the soil is dry and rotate the tree monthly.
Winter fertilizers are available for orange and citrus trees with the optimal mix of elements for your tree. Follow the directions carefully, to ensure you don't over-fertilize the tree.