Shrub or tree to 5 m. Branchlets conspicuously angled, with numerous straight spines, 1–2(–3) cm long. Leaves evergreen, leathery, 8–11.5 × 1.8–3 cm (lamina), ovate to elliptic, secondary veins indistinct, margins entire to crenate, apex acuminate and often emarginate; petiole winged and foliose, often wider than the lamina, 3.5–6 × 2–3 cm, obovate to spathulate. Flower solitary and axillary, 2.5–3 cm diameter, white, 5-merous, prominently glandular. Pedicel 0.4–0.6 cm long, calyx thick and fleshy, petals 1.2–1.8 cm long, stamens 20. Fruit subglobose, resembling a large, squat lemon, 8–11 × 7–10 cm, skin rough, segments 8–11. Swingle 1913. Distribution CHINA: Guizhou, Hubei, Sichuan; INDIA: Assam (Khasi Hills). Habitat Between 500 and 3000 m asl. USDA Hardiness Zone (7b–)8–9. Conservation status Not evaluated. Illustration Swingle 1913; NT258. Cross-reference K335. Taxonomic note Recent research has shown C. cavaleriei to be the prior name for this species, thus displacing the familiar name C. ichangensis (Zhang & Mabberley 2008).
Citrus cavaleriei has perhaps the longest track-record in cultivation of any hardy Citrus, having been grown (as C. ichangensis) at the Hillier Gardens for over 30 years (Hillier & Coombes 2002) – now as a newer specimen replacing the famous old tree, which died for no obvious reason (A. Coombes, pers. comm. 2006). Despite this long history in cultivation, however, it remains seldom seen, and is not currently offered by British nurseries. It is available from a handful of nurseries in the western United States, and seems to flourish both in temperate parts of the West Coast and in the southern states. A 2 m plant (planted out in 2000) observed at the JC Raulston Arboretum in 2006 looked extremely healthy and vigorous, making a solid bush of dark green, although there were no signs of flowers or fruits. A conspicuous feature is the very large wing on each side of the petiole, which may be expanded to be larger than the true leaf. An important factor in the hardiness of this species is the ripening of its wood, which is helped by hot summers. When ripening is successful it can survive temperatures below –18 ºC, but around –10 ºC may be about its limit in areas with cooler summers (Hogan 2008).
Citrus cavaleriei has long been cultivated in China, especially as a stock for more edible cultivars. Frank Meyer may have been the first to introduce it to the West, collecting material in Hubei in 1917 (Valder 1999), although the name C. ichangensis was given to material collected by E.H. Wilson in western China between 1903 and 1907, from both cultivated and apparently wild plants (Swingle 1913). The fruit is considered to be more or less inedible, with little juice, though it can be used as a lemon substitute for lemonade; the Chinese value it most for perfuming rooms (Valder 1999). The floral fragrance lives up to expectations for orange-blossom (Hogan 2008).