Pensacola News Journal

For: Saturday, Dec. 27, 2003

By: Daniel E. Mullins

Extension Horticulture Agent

Santa Rosa County

Growing Citrus Can Be Rewarding but Risky in Northwest Florida

Florida is known for many things – warm temperatures, live oaks, beautiful beaches and of course, citrus fruit production. Though the state is a leader in citrus production, all species cannot be successfully grown in all regions.

Prior to the 1980s it was not unusual to see mature specimens of the cold hardy species in north Florida. Three major freezes over the past twenty years have however, eliminated most commercial citrus north of 30.5 north latitude.

Newcomers should be aware that north Florida is not in the citrus belt.

Only the most cold hardy species and cultivars should be seriously considered .for planting in the landscape.

There are three types of sweet citrus – mandarins, oranges and grapefruits. Of these, only mandarins have sufficient cold hardiness for general use in north Florida. Satsuma (Citrus reticulata) is the most popular species. It has cold–hardiness down to about 20 degrees F., although fruit damage can occur at 25 degrees.

Kumquats are the only acid type citrus that are sufficiently cold-hardy. Lemons and limes will not tolerate our winters without protection. Meyer lemon, a relatively cold-hardy lemon hybrid will tolerate temperatures down to about 26 degrees F. Meiwa, Nagami or Marumi kumquats or the Changshou kumquat will typically survive down to 15 to 20 degrees F.

Anyone growing citrus along the northern Gulf Coast should prepare to implement both active and passive methods of cold protection. All trees grown here and anywhere north of Ocala should have been grafted on trifoliate orange (Poncirus trifoliata) rootstocks. This species, when used for rootstock, confers the greatest degree of cold hardiness.

Among passive methods, site selection is the most critical. Trees should be planted on the south side of homes or other structures, or windbreaks must be provided to minimize exposure to north or northwest winds.

Cold damage can also be minimized by following some annual cultural practices. Do not fertilize after July. A late application of fertilizer can stimulate a new flush of growth in the fall that is especially susceptible to freeze damage. Each December the trunks of young trees should be insulated with a commercial tree wrap or mounded with sandy soil to a height of two feet. This protects the trunk so that even if the branches freeze back, the tree will be able to re-sprout from dormant buds on the trunk above the graft. Remove the wrap or mounded soil each spring.

When temperatures below 25 degrees F. are predicted, additional protection should be considered. A day prior to the freeze, thoroughly wet the soil around your trees. Wet soils retain more heat than dry soil and provide a degree or two of additional protection.

A method often used to protect a few trees or extra valuable trees involves erecting a portable shelter over them just prior to the freeze. Placing an incandescent light bulb in the shelter can help prevent winter damage under the worst conditions. The shelter should be removed during late morning as soon as temperatures moderate.

Information for this article was compiled by Dr. Peter Anderson and Dr. Gary Knox of the North Florida Research and Education Center in Quincy, Florida. They have collected data related to citrus cold hardiness and freeze damage for years at Monticello, Florida.

Note: I am aware that there are some home owners in Gulf Breeze and other coastal areas along the northern Gulf Coast that are successfully growing the more cold sensitive citrus in their yards. And, I have even been invited on one occasion to pick a few of their navel oranges and grape fruits!

In all cases such warm citrus growing sites were found to be near the bay or sound, and the temperature moderating effects of a large body of water. Also, the largest trees that I have seen were in a special micro-climate, protected by a solid fence or other structure.

Though citrus growing is enjoyable and can be rewarded with delicious fruit, stay alert! I have seen winters when temperatures reached the teens along the coast, single digits twenty miles inland and near zero in northern Santa Rosa County.