Cold-hardy citrus is citrus with increased frost tolerance and which may be cultivated far beyond traditional citrus growing regions. Citrus species and citrus hybrids typically described as cold-hardy generally display an ability to withstand wintertime temperatures below −5 to −10 °C (23 to 14 °F). Cold-hardy citrus may be generally accepted 'true' species (e.g. Satsuma mandarin, Kumquat) or hybrids (e.g. Citrange) involving various other citrus species. All citrus fruits are technically edible, though some have bitter flavors often regarded as unpleasant, and this variability is also seen in cold-hardy citrus fruits. Those listed as "inedible fresh" or "semi-edible" can (like all citrus) be cooked to make marmalade.
Varieties of true citrus considered cold-hardy, ordered from most to least hardy:
|Trifoliate orange (Poncirus trifoliata)||−30 °C (−22 °F)||Inedible fresh||Used as rootstock and will freely hybridize with true citrus.|
|Ichang papeda (Citrus ichangensis)||−15 °C (5 °F)||Inedible fresh||Parent to a number of hybrids, including the yuzu, sudachi, ichang lemon/shangjuan, and others.|
|Jiouyuezao mandarin (Citrus reticulata 'Jiouyuezao')||−13 °C (9 °F)||Edible||Long cultivated in China|
|Kumquat (Fortunella japonica)||−12 °C (10 °F)||Edible||Fruit eaten whole with a sweet skin and sour pulp.|
|Changsha mandarin (Citrus reticulata 'Changsha')||−11 °C (12 °F)||Edible but seedy.||Long cultivated in China|
|Chinotto (Citrus myrtifolia)||−8 °C (18 °F)||Edible. Used in cooking, too bitter to eat raw.||Long cultivated in Southern Italy, Malta and Libya.|
|Satsuma (Citrus reticulata 'Unshiu', syn. Citrus unshiu)||-5 °C
|Edible; Excellent||Long cultivated in China|
Interspecific hybrid varieties considered cold-hardy, ordered from most to least hardy:
|Citrandarin (Citrus reticulata × Poncirus trifoliata) e.g. Cultivar US852||−18 °C (0 °F)||Semi-edible||'Changsha' citrandarin is the hardiest citrus hybrid.|
|Citrumelo (Citrus × paradisi × Poncirus trifoliata)||−15 °C (5 °F)||Semi-edible||'Dunstan' is considered the most edible citrumelo.|
|Citrange (Citrus × sinensis × Poncirus trifoliata)||−15 °C (5 °F)||Semi-edible||'Rusk' is considered the most edible citrange.|
|Citrangequat (Fortunella japonica × Citrange)||−15 °C (5 °F)||Edible||'Thomasville' is considered the most edible citrangequat.|
|Yuzu (Citrus ichangensis × Citrus reticulata)||−12 °C (10 °F)||Used in cooking.||Long cultivated in Japan, where many cultivars have been developed.|
|Orangequat (Citrus sinensis × Fortunella japonica)||−9 °C (16 °F)||Edible||'Nippon' is favored for edibility and hardiness.|
- Isolation of genes from cold acclimated Poncirus trifoliata and Citrus unshiu (Abstract)
- China/FAO Citrus Symposium Mandarin-like Hybrids of Recent interest for Fresh Consumption. Problems and Ways of Control.
- Sauls, J. W., & Jackson, L. K. Cold-Hardy Citrus for North Florida. Document FC-36. University of Florida, IFAS Extension.
- Hardy citrus for the southeast.
- Cold Hardy Citrus and Hybrids. Limette (Newsletter Citrus Friends Europe) 8: 1–2.