Acer triflorum Komar.

Native to parts of northern China and the Korean peninsula, the date of introduction of Acer triflorum is often give as 1923 (e.g. Rehder 1927–1940; Bean 1976; van Gelderen et al. 1994; Harris 2000), without further detail. However, the correct year of introduction is 1917, from seed collected by Ernest Wilson in Korea. As quoted in Spongberg (1990, p.222), Wilson wrote to Sargent of his collections in a letter dated October 22nd that ‘perhaps the best capture was A. triflorum. This makes a large tree and has loose, papery, reddish-gray bark and wonderful autumn tints of yellow and orange’. Wilson’s notes from his first expedition to Korea and Manchuria in 1917 confirm that he collected Acer triflorum three times on this trip, and though there are no corresponding plants at the Arnold Arboretum, which he was working for at the time, material appears to have made its way to UK collections. W 9303 corresponds to the (previously unrecognised) reference number recorded in the notebook of the then Westonbirt Head Gardener Arthur Chapman alongside the species name of Acer triflorum (Crowley 2016). It is likely that an old individual of the species growing at the southern end of Westonbirt’s Holford Ride represents this original introduction, though conclusive evidence is lacking. This tree was measured at 10 m tall in 2024 (The Tree Register 2026). Reference is also made to material of W 9303 in Albert Bruce Jackson’s Catalogue of Trees and Shrubs at Borde Hill (Jackson 1935), though living material is absent from more recent records and appears likely lost.

Attaining smaller dimensions in cultivation than recorded in the wild, the species has been introduced to North American collections numerous times from both China and Korea. Plants grown from seed collected on the 1997 NACPEC Changbai Shan expedition are held at numerous collections in the United States. NACPEC 97108 is reported from the Dawes Arboretum, Morris Arboretum and the Arnold Arboretum, with plants from NACPEC 97112 also at the latter (American Public Gardens Association 2017). The species is also well represented at The Morton Arboretum, including material from the 1993 NACPEC expedition to Heilongjiang (HLJ 042). Material from the same collection is also present at the Morris Arboretum (American Public Gardens Association 2017). Here also grows Korean-sourced material collected under KNW 1007 from Namyongju-Gun collected on a 1984 expedition (American Public Gardens Association 2017). Plants grown from material shared by Chollipo Arboretum form part of the collection at the Arnold Arboretum (American Public Gardens Association 2017). Growing adjacent to Chinese-sourced plants outside the Hunnewell Building are two fine specimens ultimately of Korean provenance, though of indirect origin (Arnold Arboretum 2020). There are also several plants at Arboretum Wespelaar, Belgium, that are also of cultivated origin.

While the species is grown in several collections in the UK, there are far fewer wild-sourced individuals recorded here. Wild plants from Beyer, Erskine & Cowley’s Expedition to Korea in 1982 (BECX 02) are at RBG Kew and the Castle Howard Arboretum, though the UK champion grows at Corsham Court, Wiltshire, standing at 13 m tall in 2016 (The Tree Register 2026). A rival at Lanarth, Cornwall, was measured at 12.6 m tall in 2024 (The Tree Register 2026).

Best grown on moist, free draining, acidic soils, Dirr & Warren (2019) rank Acer triflorum as the finest of the trifoliolate maples, ahead of hybrids with A. griseum and between A. griseum and A. maximowiczianum. Reasonable comparison between all of these taxa in the UK cannot be made, however, given the current rarity of hybrids. Certainly, A. triflorum performs fantastically well in parts of the United States, reliably producing vibrant autumn colour (pers. obs.). Mature specimens develop a rounded crown and its attractive scaly bark develops at a young age and though slower growing than A. griseum, it is also the most cold hardy of the group (Dirr 2011). Dirr & Warren (2019) suggest that its suite of attributes would render the species a staple in North American gardens were it more widely available. However, like other members of Sect. Trifoliata, its seed has low viability, hence its scarcity in the trade.

Performance in Britain is variable. Bean (1976) suggested that the species might perform better with warmer summers (as plants growing in eastern North America indicate) while Sir Harold Hillier, quoted there (p. 238) described an individual that ‘gives consistently excellent autumn colour, being one of the best trees for this purpose in the nursery’. Specimens growing in the southeast are seemingly appreciative of greater summer heat than those further west and colour strongly, while individuals at Westonbirt are often unspectacular. Though Bean (1976 p. 238) describes two trees on Mitchell Drive ‘whose leaves die off brilliant crimson’ (at least one of which no longer remains), specimens there never rank among the finest of the maples for autumn colour. However, a warmer climate may suit the species and greater experimentation with known origin material would be highly desirable.

In recent years Acer triflorum has become available through specialist nurseries in Europe, including the UK, at very large sizes for instant landscaping and is proving quite popular for this purpose (T. Christian, pers. comm. 2025). Like other members of the section, A. triflorum is quite at home on alkaline soils, including shallow chalk.