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Acer negundo 'KELLY'S GOLD' ash-leaved maple, boxelder
Acer
The genus Acer belongs among woody plants that appeared very early in the Northern Hemisphere, and whose basic form has changed remarkably little since then, unlike many other tree groups. Tertiary fossils from Europe, Asia and North America already show leaves and fruits that would be instantly recognisable today, including the characteristic paired samaras. In Czechia, one of the best known fossil sites is Bílina, where petrified maple leaves and fruits from the late Tertiary period testify that these trees were part of the local landscape long before the arrival of humans. Scientifically, the genus was described by Carl Linnaeus (1707–1778) in his seminal work Species Plantarum in 1753, although its internal classification has been repeatedly revised since then. Today, botanists regard East Asia, particularly China, Japan and the Himalayan region, as the true centre of species diversity within the genus. Maples occupy an exceptionally wide range of habitats, from subtropical mountain forests to the cold regions of the temperate zone. They are among the trees that have accompanied human landscapes and cultures for a very long time.
Acer negundo, ash-leaved maple or boxelder, originates from North America, where it formed part of the everyday life of Indigenous peoples as well as later European settlers for centuries. It naturally grows along rivers, in floodplains and in open woodlands, where it functions as a fast growing and highly adaptable tree. At times when sugar maple was not readily available, sugar was commonly produced from its sap, albeit with lower yields and a milder flavour. The species was introduced to Europe in 1688, when it was cultivated in the gardens at Fulham near London by Henry Compton (1632–1713), one of the most important introducers of North American woody plants of his time. From there, boxelder gradually spread into botanical gardens and parks throughout Europe. In what is now the Czech Republic, it has been documented since 1835, when it appeared in the Royal Game Reserve in Prague’s Stromovka, from where it quickly spread into castle parks, urban greenery and the open landscape. Often this spread was not intentional. Based on long term scientific studies, boxelder has been shown to possess a high degree of invasiveness, which has led to the botanical species being excluded from recommended plantings and actively removed in many locations. In horticultural practice, therefore, only selected, predominantly sterile cultivars are used, as they do not pose a comparable risk to surrounding vegetation.
Kelly’s Gold is a cultivar of boxelder maple that I first encountered around 2012 in a small town in South Bohemia. Not a single tree, but an entire avenue glowing like the summer sun. This maple wins you over with its brilliant golden yellow foliage, which appears dominant in any landscape. Over the course of the season, however, the leaf colour gradually changes. In spring, the youngest leaves are salmon pink, in summer, they take on light green tones, and in very warm regions the golden hue may disappear entirely during summer, allowing the tree to protect itself from leaf scorch. The leaves are deciduous and pinnately compound, usually consisting of three to five ovate leaflets with shallowly toothed margins. They are smaller than those of the botanical species, giving the tree a lighter and more delicate overall appearance.
Growth is relatively fast, especially in youth, when the tree readily responds to sufficient moisture and nutrients. In its early years, it produces long, softer shoots and quickly gains volume, making it a visually prominent element shortly after planting. The crown is initially rather irregular, loose and broadly spreading, with branches emerging at various angles. Over time, however, it becomes more rounded, developing a soft, umbrella like to semi spherical form. In maturity, it typically reaches a height of 6 to 9 metres, with a comparable spread. It therefore appears as a medium sized tree with a pronounced horizontal presence rather than a slender vertical accent. This combination of rapid growth, a spreading crown and light coloured foliage allows it to fill space very quickly and with strong visual impact, sometimes excessively so.
The cultivar ‘Kelly’s Gold’ was introduced into cultivation by the Duncan and Davies Nursery in New Zealand, as reported by Jacobson (1996), and its precise origin remains unclear. Some authors, such as Hatch (2021–2022), question whether it is truly distinct from the older form ‘Auratum’, while van Gelderen and van Gelderen (1999) consider it inferior and prone to sun damage, something we have not observed locally. Practical observations by Dirr and Warren (2019), however, point to pronounced greening of the foliage as the season progresses, particularly in warmer regions. ‘Kelly’s Gold’ thus represents more of a historical milestone in the development of yellow leaved boxelder cultivars than a reliably golden selection throughout the entire growing season.
Boxelder maple requires virtually no maintenance. It is resistant to severe frost, wind, drought and temporary waterlogging. It is not prone to diseases and thrives in full sun as well as partial shade. It performs best in deeper, moist but well drained soils, yet it also tolerates drier sites and urban conditions. During the first three years after planting, the tree must be firmly staked to ensure proper anchorage and straight trunk development. During this period, grass and other plants should not be allowed to grow above the root zone. Pruning is not necessary, but it is possible, ideally in late winter before sap flow begins. Trees or shrubs subjected to regular renewal pruning develop dense branching with large leaves, enhancing their ornamental value. Frost hardiness is excellent, tolerating temperatures down to approximately −45 °C (USDA zone 2).
Last update 09-01-2014; 21-02-2026
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