Acer griseum (Franch.) Pax

Perhaps the most charismatic of all maples, and indeed among the most ornamental of all temperate trees grown in our gardens, there has been much interest and much written about Acer griseum since its introduction to horticulture in the early 1900s. No other maple is more lauded for the characters of its bark, foliage and suitability for use in garden settings.

The following account of the species serves as a summary of its history and use in cultivation, and leans heavily on the International Dendrology Society’s Tree of the Year article written by Tony Aiello and colleagues, who have studied the species both in cultivation and in the wild over the last decade or so (Aiello et al. 2021). This comprehensive chronicling of the species’ introduction to cultivation, its propagation and wild status should be referred to for additional information of this popular yet poorly understood species. Though commonly used as a garden tree across our area, Acer griseum is threatened with extinction in the wild, with a disjunct population lacking regeneration (Aiello & Crowley 2019).

First collected by Père Paul Guillaume Farges (Farges 955), the species was introduced to both Europe and North America by Ernest Wilson, who made wild collections of the species in 1901 and 1907 (Sargent 1913). On encountering wild individuals, Wilson (cited in Spongberg 1990) described the species as ‘easily the most outstanding of all Chinese maples and one of the most distinguished of [its] large and varied tribe’.

As established via genetic analysis conducted by Aiello et al. (2021), the vast majority of trees grown on both sides of the Atlantic derive from Wilson’s 1901 introduction, made while the Gloucestershire-born plant explorer was employed by the Veitch Nursery (Veitch seed no. 1291). The largest of all may be found in North American collections, but in the UK and Ireland the largest was a tree at Dyffryn, Wales, planted in 1911 and measuring 12 m tall and 85 cm dbh in 2018 (The Tree Register 2025), which unfortunately succumbed to honey fungus in 2019 (C. Flynn, pers. comm. 2022). However, Dyffryn remains home to many other notable specimens, including a particularly shapely individual north of the house recorded as 9 m tall and 65 cm diameter in 2018 (The Tree Register 2025). Other original plants include the fine specimen at Westonbirt’s Down Gate, which measured 6 m tall and 62 cm diameter in 2024 (The Tree Register 2025). A tree of comparable girth at Westonbirt’s Lodge Gates has been confirmed as first generation offspring, as has the shapely individual outside the north entrance of the Princess of Wales Conservatory at RBG Kew (Aiello et al. 2021). This tree, along with many others in UK collections, was grown from seed from Sir Frederick Stern’s original tree at Highdown Gardens, West Sussex, which remains today having been uprighted and staked following the great storm of 1987 (Aiello et al. 2021). While Acer griseum is often noted as having low seed viability, this individual shows impressive fertility. Likewise, trees forming part of the avenue leading to the main house at Hergest Croft provide another source of good seed, as does one in a private garden in Winchester (D. West, pers. comm. 2024). Aiello et al. (2021) note that while some trees may produce hollow seed, whether grown in groups or not, other, isolated trees are also known to reliably produce fertile seed. Suffice to say, the reproductive biology of the species is complex, and needs to be better understood to support its conservation. To circumvent problems with propagation, US nurseries have developed seed orchards using fertile trees in order to produce trees for commerce (Aiello et al. 2021).

It had been speculated by Del Tredici (2007) that two Arnold Arboretum plants – representing Wilson’s second introduction of Acer griseum, made while working for the Arnold Arboretum (W 719) – were the source of many plants growing in the eastern United States. From Hubei, one of the two plants raised grows in the Explorers Garden and is 9 m tall with an impressive diameter of 98 cm (Aiello et al. 2021). The second is 15 m tall, with a diameter of 78 cm (Aiello et al. 2021). Though perhaps logical to suggest that younger trees in the United States derive from these, Aiello et al. (2021) showed that there too, trees largely derive from Wilson’s first (1901) introduction (T. Aiello pers. comm. 2024) which made its way to the United States via scion wood from Stern’s original plant at Highdown, West Sussex.

Acer griseum is encountered across large parts of mainland Europe, with notable specimens including trees at Meise Botanic Garden, Belgium, though at Arboretum Wespelaar the species appears not always to perform to its best (K. Camelbeke pers. comm in Aiello et al. 2021). Two mature trees at Plantentuin Esveld, The Netherlands, serve as mother plants to the eponymous nursery, derived from seeds collected from trees at Hergest Croft (Aiello et al. 2021). Warming temperatures over recent decades have seen conditions at Rogów Arboretum, Poland, favour the species, with specimens that were previously cut back by winter temperatures now producing viable seed (P. Banaszczak pers. comm. in Aiello et al. 2021). The tree is reportedly common in southern Sweden with sizeable examples growing in private gardens and specimens available at garden centres (H. Sjöman, pers. comm. in Aiello et al. 2021). A tree at the Botanic Gardens of the Technische Universität Darmstadt, Germany, measured 11.8 m tall and 35 cm dbh in 2013 (Monumental Trees 2024), is thought possibly to be a Wilson original (Aiello et al. 2021). The plant may date from the early 1900s when the then head garderner, Joseph Anton Purpus, had a close association with Alfred Rehder, taxonomist at the Arnold Arboretum from 1898 and previously head gardener at Darmstadt himself, who may have provided a link to the newly introduced seed (Aiello et al. 2021). Other notable specimens in Germany include a pair exceeding 30 cm dbh at the Park Planten un Blomen, Hamburg (Monumental Trees 2024).

Athough other western collectors have observed and collected herbarium specimens of Acer griseum since Wilson’s time, no further seed introductions were made until 1994, when a NACPEC expedition to Wudang Shan, Hubei, gathered material under WD-172. Of sixteen seedlings, four trees were growing at the Morris Arboretum, Philadelphia, and three at both the Arnold Arboretum and US National Arboretum as of 2021 (Aiello et al. 2021). While collecting wild material for DNA analysis in 2015, Aiello et al. (2021) also made new seed collections from which further plants have been raised: one in northeastern Sichuan (with seedlings at the Morris Arboretum) and one from wild-sourced plants growing at Xi’an Botanical Garden (with seedlings at The Morton Arboretum) (Aiello et al. 2021). Material was also introduced to the United States from seed collected in Hubei by Dan Hinkley in 2014 (Hinkley 2014). Further wild-origin A. griseum exists at Arboretum Mustila, Finland, from seed collected in Gansu in 2010 (Aiello et al. 2021). Plants here represent the northernmost plantings of the species in Europe (Aiello et al. 2021).

Acer griseum is a slow growing tree in most of the UK, often attaining little more than 10 m height in a century or more in most parts of the UK. It appears slightly faster growing in the eastern United States, and faster again in parts of western North America. Exceptional both as a single or multi-stemmed tree, considerable variation can be seen among seed-raised plants, with dark bark becoming paler and scaly sometimes rather sooner than later. Though most plants exhibit fruits with wings held at right angles from one another, some specimens display fruits with crossing wings. Examples include two individuals at Westonbirt, and a small tree at the Dendrological Garden Průhonice, near Prague (pers. obs.). Reasonably heat resistant, and somewhat tolerant of drought, it is also reported of being capable of surviving verticillium wilt (Dirr 2011), though at what stage any infected wood may have been removed is unknown. As noted above, trees may be successfully grown from seed, or sometimes raised via grafting. Material may be grafted onto any member of Sect. Trifoliata (incl. A. griseum itself), should it be available, as well as A. pseudoplatanus or A. saccharum. Growing on alkaline substrates in its native China (Harris 2000), it performs perfectly well on both acid and alkaline soils, as do other members of its section. It is also tolerant of poor, urban soils (pers. obs).

With improved stock now available in the United States, the species has become more available in the trade than was once the case, and is finding greater use as a street tree (Dirr & Warren 2019). A small number of cultivars have been named, largely for habit rather than any improvement on already-exceptional performance. Hybrids with A. maximowiczianum (on A. griseum or. A. saccharum rootstocks) now reportedly compete with it in some areas in North America (Dirr & Warren 2019), though there is no contest regarding which has the better bark. Intersectional hybrids involving A. griseum also exist, its crosses with A. pseudoplatanus and A. saccharum providing much intrigue within the maple fraternity.