Acer negundo L.

Acer negundo as a wild tree in Minnesota, USA, August 2022. Image John Grimshaw.

Acer negundo leaves in the Ashdown Park Hotel, East Sussex, UK, May 2017. Image Ron Kemeny.

Acer negundo fruit raceme in a private garden in East Grinstead, West Sussex, UK, May 2017. Image Ron Kemeny.

Over the years several gold-leaved variants of Ace negundo have been named. This is 'Kelly's Gold'. Image John Grimshaw.

'Angustifolium'

A selection with pubescent branchlets and leaves with five, usually narrow leaflets with acuminate tips (van Gelderen et al. 1994). It was introduced by Dieck, and no longer in commerce by 1994 (van Gelderen et al. 1994).

'Auratum'

Described by Bean (1976) as ‘one of the best of golden-coloured trees’, ‘Auratum’ has glabrous, bloomed branchlets and yellow leaves, turning towards green in late summer and autumn (van Gelderen et al. 1994). It was raised by Späth’s nurseries in 1891, from a sport of ‘Aureo-limbatum’ (Bean 1976), a cultivar now lost to cultivation (van Gelderen et al. 1994). For a while ‘Auratum’ was widely thought to be the same as ‘Odessanum’, though Krüssmann, in Handbuch der Laubgehölze noted that this was not so (Bean 1976; van Gelderen et al. 1994). It has reportedly taken the place of ‘Lutescens’, which was very rare by 1994 (van Gelderen et al. 1994).

Acer negundo 'Auratum' at Fanhams Hall, Hertfordshire, UK; 21st June 2014. Image Owen Johnson.

'Aureomarginatum'

A large shrub or small tree with leaf margins creamy yellow, though prone to reversion like most variegated forms of Acer negundo (van Gelderen et al. 1994; van Gelderen & van Gelderen 1999). It may also have leaves entirely yellow (van Gelderen et al. (1994). It was introduced by Dieck sometime before 1885 (Bean 1976). van Gelderen et al. (1994) suggest that plants named ‘Aureonotatum’ and ‘Aureomaculatum’ may be best placed either here or under ‘Aureovariegatum’. The latter is also not always distinguished from this cultivar (van Gelderen et al. 1994).

'Aureovariegatum'

A clone with yellow-spotted and somewhat yellow-margined leaves, and prone to reversion (van Gelderen et al. 1994). It was introduced by Späth’s nurseries in around 1887 (van Gelderen et al. 1994), and grown in Canada before the end of the 19th century, but not in the United States until 1960, when material was imported from Britain to the Arnold Arboretum (Jacobson 1996).

'Barabit's Compact'

A compact clone with a rounded crown, presumed by Hatch (2021–2022) to have originated at Barabit’s Nursery in Hungary.

'Baron'

A very hardy, sterile selection made by Morden Research Station, Manitoba (Jacobson 1996), from plants growing near Saskatoon, Saskatchewan (van Gelderen et al. 1994). Suggested as useful as a street tree by van Gelderen et al. (1994).

'Berrimu Sterile'

Originating in New Zealand and presumed by Hatch (2021–2022) to be a male clone, as the name would suggest.

'Chrysophyllum'

A vigorous male with five, three-lobed leaflets showing golden-yellow variegation (van Gelderen et al. 1994). Of German origin, it was considered rare in 1994 (van Gelderen et al. 1994), and is absent from more recent texts.

'Crispum'

A shrubby male clone with curled, often deformed leaflets (Bean 1976). In cultivation before 1825. Included by Bean (1976) but later thought by van Gelderen et al. (1994) to no longer be in cultivation.

'Crispum Variegatum'

A selection apparently with cream margins and thought not to be in cultivation (van Gelderen et al. 1994). Included here on account of Krüssman’s mention that it was common in Dutch parks, a claim strongly refuted by van Gelderen et al. (1994).

'Dr. Herskalt'

A bushy tree of somewhat untidy form, with three or five leaflets (van Gelderen & van Gelderen 1999). Reportedly present only at Westonbirt (van Gelderen & van Gelderen 1999), though no longer grown there.

'Elegans'

A slow-growing tree with a dense crown and small leaves with cream-yellow margins (van Gelderen et al. 1994). It has bloomed new shoots (Bean 1976), and is described as a very elegant and attractive plant for smaller gardens (van Gelderen et al. 1994). It is of French origin and was available before 1901, when it was named by Schwerin (van Gelderen et al. 1994). Hatch (2021–2022) lists ‘Elegantissimum’ as a synonym, though van Gelderen et al. (1994) suggest that plants under this name are indistinguishable from ‘Variegatum’.

'Flamingo'

A large shrub or small tree with leaves variegated white and pink, most apparent in spring (van Gelderen & van Gelderen 1999). Raised by J. Bastiaanse in the Netherlands in 1976 and given a Royal Boskoop Horticultural Society Award of Merit the following year, and the RHS AGM in 1993 (van Gelderen & van Gelderen 1999). Though described by van Gelderen & van Gelderen (1999) as ‘one of the best cultivars developed since the 1970s’ it still requires some pruning to maintain its variegation. This form has superseded ‘Schwerinii’, which was thought lost in cultivation by 1994 (van Gelderen et al. 1994). It responds well to coppicing and can make a fine foliage feature among lush herbaceous plantings.

Acer negundo 'Flamingo' beautifully paired with a purple-leaved Canna at RHS Garden Harlow Carr, Harrogate, UK (August 2021). Image John Grimshaw.

'Giganteum'

Noted for its large leaves, reaching up to 40 cm long, comprising seven to nine leaflets (van Gelderen et al. 1994).

'Heterophyllum'

Included by Bean (1976) as a selection with linear or lanceolate leaflets sometimes with deeply cut margins, introduced by Späth’s nurseries in 1883. van Gelderen & van Gelderen (1999) treated ‘Laciniatum’ as a synonym, after van Gelderen et al. (1994) treated ‘Heterophyllum’ as a synonym of ‘Laciniatum’.

'Kelly's Gold'

Introduced by Duncan and Davies Nursery, New Zealand, this very popular cultivar has glaucous branchlets and golden-yellow leaves (Jacobson 1996). Its distinctness from ‘Auratum’ is queried by Hatch (2021–2022); van Gelderen & van Gelderen (1999) consider it inferior, and prone to sun damage. This is supported by Dirr & Warren (2019) who note that the leaves turn greener as the season progresses, and in Georgia are completely green in summer, as a result of the heat there.

Acer negundo 'Kelly's Gold' (US National Botanical Garden, April 2009). Image John Grimshaw.

Acer negundo 'Kelly's Gold' used to great effect among other lush foliage at RHS Garden Harlow Carr (August 2021). Image John Grimshaw.

'Luteopictum'

Described by van Gelderen et al. (1994) as an old, occasionally available clone, with purplish young shoots and leaves with a yellow-green central blotch.

'Odessanum'

A vigorous cutivar with pubescent branchlets and leaves that are golden yellow in full sun, and pale green in shade (van Gelderen et al. 1994). First sold by Rothe’s nursery of Odessa, Ukriane, in 1890 (Bean 1976). Described as very rare in North America by Jacobson (1996) and of unknown availability by van Gelderen et al. (1994). It has been confused with the more common ‘Auratum’ and its status in cultivation is unknown (van Gelderen et al. 1994).

'Rubescens'

Noted for its red-tinged new growth, with branchlets turning from brownish green to purple (van Gelderen et al. 1994).

'Sensation'

A cultivar with a good branching structure not always associated with the species, developing an oval crown and suitable for use as a street tree (van Gelderen et al. 1994; Dirr & Warren 2019). It has reddish-tinged new growth, becoming green in summer before steadily turning red in autumn (van Gelderen et al. 1994; Dirr & Warren 2019). Described by Dirr & Warren (2019) as ‘a cultivar that really gets it right’, it was introduced by Frank Schmidt Nurseries in 1989 (Hatch 2021–2022).

Richly coloured foliage on Acer negundo 'Sensation' (Westonbirt National Arboretum, UK, June 2012). Image John Grimshaw.

subsp. californicum (Torr. & Gray) Wesm.

Acer negundo subsp. californicum is represented in collections on both sides of the Atlantic, though plants under this name are not frequently encountered. Recent introductions to Europe include those made under ORCA 340–344 inclusive in Lake County, California by staff from Bedgebury and and Wakehurst, UK, with plants growing at RBG Edinburgh, RBG Kew and Bedgebury. Older examples grow at Westonbirt, planted in 1985, stood at approximately 9 m tall as of February 2023. A single individual at the University of Washington Botanic Garden was recorded as part of the American Public Gardens Association Plant Collection Network Acer Multisite in 2017 (American Public Gardens Association 2017). The two varieties included here within subsp. californicum are more widespread than the nominate variety, which is apparently restricted to California (Grimshaw & Bayton 2009).

Under his entry for var. californicum, Bean (1976) states that this taxon ‘should not be confused with A. negundo californicum Hort. (var. pseudo-californicum Schwer.), which appears to be no more than a strain, in cultivation since before 1864, characterised by its great vigour and by having the young branchlets green, as in the type, but covered with a pruinose bloom…’. van Gelderen et al. (1994) include a cultivar ‘Pseudo-californicum’ (syn. ‘New California’), stating that this name refers to ‘all forms with green shoots’ (p. 267). Given that these descriptions may describe material referrable to taxa other than subsp, californicum, plants occuring under such names should be properly scrutinised.

var. arizonicum Sarg.

Given the relatively limited distribution of this taxon, but more pertinently its omission from several texts, it is unsurprising that there is little material so named in collections. It is likely however that some material grown as subsp. californicum may fit here.

var. texanum Pax

This taxon is well represented in collections, grown variously as subsp. or var. interius, as well as under the name used here. It is likely that there are plants in collections that have not been identified to infraspecific level that also belong here.

Its natural distribution is difficult to trace owing to the various interpretations of the species, and introgression with other forms across the range. Grimshaw & Bayton (2009) and Vargas-Rodriguez et al. (2020) state a more restricted distribution in the United States than given here, though it is generally accepted to be a widespread form across its range, except in Mexico where it is recorded from a single locality (Vargas-Rodriguez et al. 2020).

subsp. mexicanum (DC.) Wesm.

Acer negundo subsp. mexicanum is the southernmost maple in the Americas, with its presence in Honduras established by Vargas-Rodriguez et al. (2020). It has a fragmented wild population, but within its range has uses including for hedging and erosion prevention, while its branches are used in Christmas nativity displays, and its leaves as a substrate for avocado seed germination Vargas-Rodriguez et al. (2020).

Grimshaw & Bayton (2009) speculated that a collection made from Pico de Orizaba, Puebla, Mexico (F&M 48) may have been the first introduction of this subspecies into cultivation. At that point it was considered too early to appraise its horticultural potential, though plants have proved hardy since, including at Bedgebury Pinetum (Kent, UK) and in the coild upland conditions of Colesbourne Park, Gloucestershire, UK. Their bloomed stems and leaves that flush red and retain red petioles and rachis are striking, and easily distinguish it from other Acer negundo taxa. It is also grown in Belgium, including at Arboretum Wespelaar and at the University of Ghent Botanic Garden. That at Ghent is also F&M 48, while the plant at Wespelaar was originally sourced from Plantentuin Esveld (J. Ossaer, pers. comm. 2023), and though young (planted in 2022) is proving vigourous (K. Camelbeke, pers. comm. 2023).

The contrast between the glaucous stems and bright red petioles of Acer negundo subsp. mexicanum adds a new twist to a familiar species. Image Nick Macer.

Acer negundo subsp. mexicanum of wild Mexican origin at Bedgebury National Pinetum, UK. Planted in an open, sunny spot in 2008, the subspecies has thrived here, with foliage at least as luxuriant and attractive as the best selections of the Violaceum Group; it was 9 m tall and wide in August 2024. Image Owen Johnson.

'Tadeusz Szymanowski'

A male clone with bright green, deeply cut leaflets, sometimes very nearly to the midrib (Hatch 2021–2022). It originated in Poland and has become quite widely available in central Europe in recent years.

'Variegatum'

Described by Bean (1976) as then being ‘one of the commonest of variegated trees, once largely used in town gardens and grown in pots for the decoration of halls and large rooms.’ Less frequent now, it makes a small tree of vigorous growth when young. The leaves are bordered creamy-white, or are sometimes entirely so (Bean 1976; van Gelderen et al. 1994). It produces fruit which may also be variegated, but the seeds are always sterile (van Gelderen et al. 1994; Dirr & Warren 2019). It first appeared as a sport on a green-leaved individual in a nursery at Toulouse in 1845 (Bean 1976; van Gelderen et al. 1994). It is considered the best variegated selection by Dirr & Warren (2019) and one of the best variegated maples by van Gelderen & van Gelderen (1999) though these authors note that like other variegated forms it is prone to reversion.

'Versicolor'

A male clone with bloomed shoots and dark green leaves with pale margins that later turn yellowish, though this variegation is only retained on shaded growth (van Gelderen, de Jong & Oterdoom 1994).

Violaceum Group

A selection named by Miller in 1826, later treated as a wild variety as similar forms are common in the midwest United States (van Gelderen, de Jong & Oterdoom 1994). Plants labelled var. violaceum (under which it has been awarded an AGM; Edwards & Marshall 2019) are not uncommon in collections. Given that it has numerous origins, cultivated material is probably best considered as belonging to a Group, which is the position adopted here, though formal publicaton is still needed (May 2024). Plants can be vigorous and attain greater proportions than most other Acer negundo forms, making them unsuitable for smaller gardens (van Gelderen & van Gelderen 1999). Their leaves usually have 5–7 leaflets and are softly pubescent beneath (van Gelderen, de Jong & Oterdoom 1994). Its importance in horticulture comes from its purplish young branchlets covered with a glaucous bloom, and that the filaments are pinkish-red, giving a striking effect when it is in flower in early spring (Bean 1976).

Acer negundo Violaceum Group in full flower in March 2012 (Pyrford, Surrey). Image John Grimshaw.

The pinkish-red filaments, hanging down in long tassels, give Acer negundo Violaceum Group a moment of glory in spring (Pyrford, Surrey, March 2012). Image John Grimshaw.

'Well's Golden'

A selection of New Zealand origin with golden yellow leaves, and scarcely distinguishable from ‘Kelly’s Gold’, itself very close to ‘Auratum’ (Hatch 2021–2022).

'Winter Lightning'

A selection with bright green leaves and yellow stems in winter (Frank P Matthews 2021). It is used to great effect as a coppice plant at the Savill Garden, Windsor Great Park, and at RHS Garden Wisley, both Surrey, UK, where it is regularly coppiced to stimulate long extension growth in the manner of Cornus and Salix grown for their coloured winter stems (pers. obs. 2024). It also shows good yellow autumn colour, but in summer the leaves are the species’ normal dull green.

Acer negundo 'Winter Lightning' in autumn: yellow-green stems, yellow leaflets, pink petioles (RHS Garden Wisley, UK; 20 October 2010). Image Julian Sutton.

Acer negundo 'Winter Lightning' coppiced annually (RHS Garden Wisley, UK; 20 October 2010). Image Julian Sutton.