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Tree to at least 20 m. Bark pale grey, ridged in maturity. Twigs slender, becoming glabrous and shining green. Buds large (7–11 mm long), with 2 exposed scales of equal length, glabrous except near the tip. Petiole long (4–9 cm), nearly glabrous; leaf broadly ovate, 6–16 × 5–10 cm, variably tomentose beneath (stellate hairs with 4–9 arms) or yellow-green and hairless except for brown axillary tufts; marginal teeth regular, shallow and step-like, with mucronate tips 0.5–1.3 mm long. Floral bracts narrowly oblanceolate, 6–16 × 1.3–2.3 cm, often almost stalkless, with some stellate hairs. Inflorescence drooping, with 9–12 flowers on a long hanging peduncle; staminodes present. Fruit narrowly obovoid, prominently 5-angled, 1–1.2 × 0.7 cm, tomentose, apex pointed; fruit-wall woody. (Tang et al. 2007; Pigott 2012).
Distribution China Sichuan; Yunnan
Habitat Forests, 1800 - 2800 m.
USDA Hardiness Zone 7
RHS Hardiness Rating H5
Conservation status Vulnerable (VU)
Tilia callidonta is known from just four localities in northern Yunnan and western Sichuan, and is a rare tree in cultivation. Its native area experiences relatively cool, moist summers but rather dry winters (Pigott 2012).
A member of Section Astrophilyra, its leaves are grey- or white-felted underneath to a varying degree. As Chang’s specific epithet (from the Greek kallos – beauty, odontos – tooth) implies, the leaves’ small, step-like, awn-tipped serrations are perhaps the most orthodontically perfect the genus has to offer. The shape of the fruit appears consistent; this and the longer-stalked flowers in larger heads help distinguish the species from the more widespread and very variable T. chinensis.
The species was introduced by Donald Pigott in 1993 from Sichuan, and grows in his garden at Cartmel, Cumbria. Another collection from the same area by Peter Cox and Steve Hootman (CH 7016) was identified by Pigott from a specimen sent to him by Roy Lancaster in 2014 (Lancaster 2015) from a tree at Glendoick, Perthshire. This has grown superbly, reaching 9 × 0.22 m dbh by 2017 (Tree Register 2018). The Glendoick tree is more slenderly branched and open-crowned than most limes, but the ace-of-spades shaped crown, on a straight stem, is characteristic of the best; the underleaf is exquisitely silvered. However, the species has languished in Keith Rushforth’s Devon garden, reaching only 1.3 m after 13 years (Tree Register 2018). When grown in western Britain it tends to emerge early; the young growth is then quite easily damaged by frost (Pigott 2012). We have been unable to locate specimens in continental Europe or North America.
T. callidonta scions appear incompatible with T. cordata, a popular rootstock. However, T. chinensis is mutually compatible. Success has been achieved by first grafting T. chinensis onto T. cordata, then grafting callidonta onto the chinensis scion, an most unusual example of an inter-stem graft (Humphrey 2019).