Raising citrus in USDA cold hardiness zone 8a–outside of the traditional citrus-growing regions–is made difficult both by minimum winter temperatures, and by fluctuations in temperature that interfere with citrus achieving maximum winter hardiness. However, a four-year evaluation of citrus cultivars in Savannah, Georgia when the winter temperatures dipped to between 13 and 18 degrees F. suggests several possibilities. (See “Field Evaluation of Cold Hardy Citrus in Coastal Georgia” by M. Rieger et al., HortTechnology Vol 13, No.3, 2003). Among the survivors were the mandarins ‘Owari’ (grafted on sour orange rootstock) and ‘Changsha’ (own-rooted), a citrangequat ‘Mr. Johns Longevity’ (both own-rooted and grafted on ‘Carrizo’ citrange rootstock), and the orangequat ‘Nippon’ . These plants experienced some defoliation and minor shoot dieback, but they fruited consistently on an annual basis.
To improve any citrus plants chance of survival, plant in a well-drained location in full sun, preferably at the top of a southfacing slope with protection from prevailing winter winds. Planting in raised beds will improve drainage and will encourage the soil to warm up more quickly.
Young trees are less cold tolerant than mature trees, so care during first three growing seasons after planting is critical for their long term survival.
Keep the tree well-watered and avoid fertilizing between Aug 1 and Feb. 15 to avoid encouraging growth that can be injured by frosts. For more information about growing citrus and other tender plants visit the Southeastern Palm and Exotic Plant Society web site. Also, see Hardy Citrus for the Southeast by Tom McClendon. The following chart prepared by Tom McClendon appeared in the Southeastern Palms newletter (Spring 2011, Vol 19-1). Reprinted with permission.
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