Acer amamiense Yamakazi

A recent introduction and indeed a recent discovery, Acer amamiense was described in 2000, having been found by Hiroshi Yamashita the previous year (Yamazaki 2000). Restricted to a single hillside only metres from the sea in western Amami Ōshima, the wild population consists of just twelve mature trees, its habitat bisected by a road and formerly terraced for Cycas revoluta cultivation (pers. obs). However, seedlings of the maple were abundant in spring 2024 (pers. obs), and the area is now protected by the local community (I. Saeki, pers. comm. 2024). Nevertheless, the species clearly remains perilously close to extinction as a wild plant and is categorised as Critically Endangered (Crowley et al. 2020).

The species arrived in UK cultivation courtesy of Mikinori Ogisu, who collected seed under OGISU 536 on Amami Ōshima in 2008. This was circulated among collection holders in southern England by Roy Lancaster, with RBG Kew, Westonbirt, Borde Hill, Windsor Great Park, White House Farm and Bedgebury among recipients. Questions around hardiness have been posed but although some plants have been lost, many have so far persisted. An individual at Borde Hill has been measured at 7 m tall and is the current UK and Ireland Champion (The Tree Register 2025). Plants at Westonbirt are of tidy form, developing an upright, spreading crown.

Plants in different collections have begun to flower, with the first recording at Westonbirt made in 2023, from 2011 plantings. Like other members of Section Lithocarpa, individuals appear to be dioecious, and Westonbirt’s only recorded female (of five surviving trees) is, as of spring 2025, fighting a honey fungus infection (pers. obs.). Another female tree grows in the Savill Garden, with persistent (and likely sterile) fruits observed in February 2024 (pers. obs.).

To date, the species’s presence in western cultivation is restricted to southern England and Poland, with material from Ogisu’s collection also sent to Rogów Arboretum. There, a single plant survives in a pot, but will not be planted in the ground (P. Banaszczak, pers. comm. 2025). Two additional plants from the same seed batch were planted at Glinna Arboretum near Szczecin, in Poland’s warmest region, where they sufffer damage but survive outdoors (P. Banaszczak, pers. comm. 2025). A new batch of seed collected in 2024 has seen further material arrive at Westonbirt in the UK, and also to the University of British Columbia Botanical Garden in Vancouver, with hopes of growing the species in more collections in support of its conservation. To date no attempts to vegetatively propagate young trees has been reported.

Acer amamiense appears closest to fellow Japanese endemic A. diabolicum. In leaf, however, it is easily distinguished by its long, wispy hairs on the petioles and lamina bases of fresh leaves. The central lobe of A. amamiense is also less toothed than in A. diabolicum (De Langhe & Crowley 2018). The flowers, often red in A. diabolicum, are yellow in A. amamiense.