Field Evaluation of Cold Hardy Citrus in Coastal Georgia

Abstract

Sixteen cultivars of citrus (Citrus spp.) and close citrus relatives were planted in Savannah, Georgia to evaluate their potential as fruiting landscape trees in an area that routinely experiences minimum temperatures of 15 to 20 °F (-9.4 to -6.7 °C) during winter. Three to six trees of each cultivar were planted in 1998, and stem dieback and defoliation data were collected in 1999, 2001, and 2002. During the 4 years of the study, air temperatures fell below 32 °F (0.0 °C) 27 to 62 times per season, with absolute minima ranging from 13 to 18 °F (-10.6 to -7.8 °C), depending on year. In general, kumquats (Fortunella spp.), represented by `Meiwa', `Nagami', and `Longevity', were completely killed (or nearly so) in their first year in the field after air temperature minima of 13.5 °F (-10.28 °C). Others experiencing 100% dieback were `Meyer' lemon (Citrus limon × C. reticulata) and `Eustis' limequat (C. aurantifolia × Fortunella japonica), which were tested twice during the study. Kumquat hybrids, including procimequat [(C. aurantifolia × F. japonica) × F. hindsii), `Sinton' citrangequat [(C. sinensis × Poncirus trifoliata) × unknown kumquat], `Mr John's Longevity' citrangequat [(C. sinensis × P. trifoliata) × F. obovat], razzlequat (Eremocitrus glauca × unknown kumquat), and `Nippon' orangequat (C. unshiu × F. crassifolia) survived freezing, but all experienced at least some defoliation and stem dieback. `Owari' satsuma (C. unshiu), `Changsha' mandarin (C. reticulata), nansho daidai (C. taiwanica) and ichang papeda (C. ichangensis) experienced only minor stem dieback but substantial defoliation in most years, except that ichang papeda was substantially damaged in the last year of the study. Seven cultivars produced fruit at least once during their first 4 years: nansho daidai, ichang papeda, `Nippon' orangequat, `Mr John's Longevity' citrangequat, `Owari' satsuma, `Changsha' mandarin, and procimequat. Based on cold hardiness, fruiting, and growth characteristics, `Owari' satsuma, `Changsha' mandarin, `Mr John's Longevity' citrangequat, and `Nippon' orangequat provided the hardiest, most precocious and desirable fruiting landscape trees in this study.