Acer pseudoplatanus L.

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Credits

Dan Crowley (2020)

Recommended citation
Crowley, D. (2020), 'Acer pseudoplatanus' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-pseudoplatanus/). Accessed 2020-09-21.

Genus

Common Names

  • Sycamore
  • European Sycamore
  • Sycamore Maple
  • Great Maple
  • Gray Harewood
  • English Harewood
  • Scottish Plane

Infraspecifics

Other species in genus

Glossary

dbh
Diameter (of trunk) at breast height. Breast height is defined as 4.5 feet (1.37 m) above the ground.
hybrid
Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies).
included
(botanical) Contained within another part or organ.
pollen
Small grains that contain the male reproductive cells. Produced in the anther.

References

There are currently no active references in this article.

Credits

Dan Crowley (2020)

Recommended citation
Crowley, D. (2020), 'Acer pseudoplatanus' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-pseudoplatanus/). Accessed 2020-09-21.

A deciduous tree to 35 m or more in the wild. Bark grey, turning pale brown and broadly plated, peeling, occasionally in longitudinal strips, with age. Branchlets glabrous, purplish red to brown. Buds ovoid, with five to ten pairs of imbricate scales, green, sometimes tipped red. Leaves chartaceous, broadly pentagonal in outline, base cordate, (three-)  five-lobed, 6–20 × 6–23 cm, lobes ovate, lateral lobes spreading, basal lobes smaller, apex acute to acuminate, margins coarsely serrate, upper surface dark green, lower surface paler, pubescent or not, often along veins but soon glabrous; petiole 6–20 (30) cm long, green or red, faintly grooved and broadening towards the base; autumn colours yellow to brown. Inflorescence terminal, narrow racemose–paniculate, glabrous, pendulous, 25–150 flowered, 10–25 cm long. Flowers yellowish green, 5-merous,sepals and petals oblong, stamens eight, inserted inside the nectar disc. Samaras to 4.5 cm long, wings spreading at acute angles or more broadly; nutlets spherical. Flowering May to June, after the leaves, fruiting in October. (van Gelderen et al. 1994; Güemes Heras & Sánchez Gómez 2015). 

 

Distribution  AlbaniaAndorraAustriaAzerbaijanBosnia and HerzegovinaBulgariaCroatiaCzechiaFranceGeorgiaGermanyGreeceHungaryItalyLiechtensteinLuxembourgNorth MacedoniaMoldovaMontenegroPolandPortugalRomaniaRussiaSerbiaSlovakiaSloveniaSpainSwitzerlandTurkeyUkraine

Habitat Mixed deciduous forests between 700 and 2000 m asl.

USDA Hardiness Zone 3-4

RHS Hardiness Rating H7

Conservation status Least concern (LC)

The most common European species of maple and designated as the type species of the genus by Linnaeus, Acer pseudoplatanus is primarily a mountain species, often growing on calcaerous substrates and, in central Europe, often in Fagus sylvatica forests (Binggeli 1994). It also grows in valleys and along streams, though avoiding the wettest soils. In different areas it is found with an eclectic mix of species, growing in the subalpine zone in Corsica with Abies alba, at lower elevations in the Balkans with Alnus glutinosa or Aesculus hippocastanum and Juglans regia, and in ravine forests of Bulgaria with Fagus orientalis and Rhododendron ponticum (Binggeli 1994). It is certainly an opportunistic species, operating as a pioneer at least in part, while also proving long-lived in many situations.

Given its broad ecological amplitude, it is unsurprising that it fares very well in many regions outside its native range. Indeed, whether it may or may not be native to Britain has been the source of much debate, though as Johnson (2015) states, its status can neither be proved or disproved. Considering the pollen record, being largely insect pollinated and avoiding wetter areas, the absence of Acer pseudoplatanus pollen from lake deposits is hardly surprising, though maple pollen does not preserve well anyway, while that of A. pseudoplatanus is reportedly indistinguishable from that of A. campestre (Green 2005). Green (2005) speculates that A. pseudoplatanus might be a component of the British flora, and that during the warmer periods of the holocene it might have retreated to cooler, mountainous areas, where it now predominantly occurs in mainland Europe, hence the long history of its presence in the north and west of Britain. It certainly supports a wealth of wildlife and is also quick to establish itself where it can, particularly in the south east, where it is described by Johnson (2015) as forming ‘evil empires of fast-growing seedlings in woods and scrubs on chalk and heavy clay’, behaving rather in the manner of an invasive.

Johnson (2015) also asserts that while the species is long-lived, even the oldest trees don’t pre-date the age of ornamental planting. Mitchell (1996) doesn’t consider it native, though disagrees with the suggestion that the species could have been introduced by the Romans, citing its inedible nature and that its timber is no better than that of A. campestre, preferring the idea that it was introduced at a time when France and Scotland had close links. Mitchell (1996) postulates that a specimen at Newbattle Abbey near Edinburgh, planted during the Reformation, suggests a date of introduction of around 1550. van Gelderen et al. (1994) suggest that the oldest tree would have been one at Kippenross, near Dunblane (current status uncertain), which was ‘well over 500 years old’. An unconfirmed report suggests that the tree known as the ‘Birnam Sycamore’ in Birnam, Scotland, may be over 1000 years old (van Gelderen et al. 1994). If true this would change things rather, while the accurate representation of the foliage of A. pseudoplatanus on the shrine of St Frideswide, in Christ Church Cathedral, Oxford, dating from 1289, raises questions as to how the species was known by the artist. Johnson (2015) suggests that it may have been grown in the garden of the monastery, but it could also have been that the carver was familiar with the tree in continental Europe.

Details of the species’ introduction to North America is rather less disputed, though not quite precise, with its arrival thought to have have been in 1803 or 1804 and ‘possibly’ by Christopher Gore (Spongberg 1990; van Gelderen et al. 1994). Spongberg (1990) suggests that he may have brought it back to the United States from London while working for Thomas Jefferson’s administration and based in London. Now common in North America, its tolerance of exposure and adaptability to any soil type is valued, though it rarely performs to its European best (Dirr & Warren 2019). In Vancouver, as in many places, the species seeds prolifically and can invade open areas (Justice, in prep). It also attracts aphids and thus is not ideal for use as a street tree.

The species is impressively tolerant of exposed sites, including maritime conditions. Windblown, heavily stunted trees, often make valuable windbreaks along parts of the British coastline and in many places form the all important first line of defence against salt-laden sea winds. This resistance is all the more interesting given that it is not accustomed to these conditions within its accepted native range. Trees of similar stature are also a familiar site in the various wind-swept uplands of the UK and Ireland, often providing the only meaningful cover around dwellings high up in areas such as the Peak District and the Yorkshire Moors.

A. pseudoplatanus is susceptible to sooty bark disease, caused by the fungus Cryptostoma corticale, and diamond bark disease canker, caused by another fungus Dichomera saubinettii, both of which can prove fatal in periods of hot, exessively dry weather (Green 2005). It is also host to sycamore tar spot, Rhytisma acerinum, which causes black splotches on the leaves. Largely a cosmetic problem, it is more prevalent outside of towns rather than in urban areas, where the common removal of leaf litter takes with it the possibility of overwintering beneath trees.

Numerous varieties and formae of the species have been named. van Gelderen et al. (1994, p. 179) chose not to accept them but included short descriptions of several considered ‘different enough to mention’. Those recognised in cultivation are treated here on account of their distinctiveness. As well as a hybrid with A. heldreichii (A. × pseudoheldreichii), A. pseudoplatanus is known to cross with A. opalus where the two overlap in the wild. So-called A. × hybridum, listed by van Gelderen et al. (1994, p. 247) as A. opalus × pseudoplatanus or A. opalus × monspessulanum, though ‘possibly nothing but an odd expression of A. pseudoplatanus’ is noted by de Jong (2011) in his account of maple hybrids as possibly A. pseudoplatanus and ignored thereafter. The same applies to A. × ramosum, listed as A. campestre × pseudoplatanus by van Gelderen et al. (1994), though ‘parentage uncertain’ (p. 248). Neither are treated here. A. pseudoplatanus is a useful rootstock for grafting other Acer species, even those belonging to different sections of the genus, when a closer relative is not available (le Hardÿ de Beaulieu 2003).

Several of Britain’s iconic trees belong to A. pseudoplatanus, including that of Sycamore Gap, along Hadrian’s Wall, and the Tolpuddle Martyrs tree, Dorset, where a group of agricultural workers swore an oath as part of their formation of a union, an act that saw them sentenced to seven years penal labour in Australia, though they were pardoned following public protests (National Trust 2019). Europe’s largest example, growing in the woods at Wamberg, Bavaria, was measured at more than 2.8 m dbh in 2019 (monumentaltrees.com 2018).


'Atropurpureum'

Synonyms
'Purpureum Spaethii'
'Spaethii'

Awards
Award of Garden Merit

RHS Hardiness Rating: H7

Described by Groinland in 1862 and introduced by Späth’s nurseries, Germany in 1883, ‘Atropurpureum’ has dark green leaves that are strikingly purple beneath van Gelderen et al. 1994; van Gelderen & van Gelderen 1999). It reached North American cultivation in around 1897, available commercially there since around 1930 (Jacobson 1996). ‘Atropurpureum’ is also commonly grown under the name ‘Spaethii’, an invalid synonym (van Gelderen et al. 1994). It is also sold by some as ‘Purpureum Spaethii’, also a synonym. Seedlings of it may also produce purple leaf undersides, while similar, invariably less distinct, forms occur in the wild and are referrable to f. purpureum. ‘Atropurpureum’ should be propagated clonely. Grown in some parts as a street tree, it is striking in the landscape, planted as both as single trees and in groups in parkland settings. Groups of five, planted at five metre spacings from one another work very well, and examples of group and individual plantings of more than a century old can be seen at Westonbirt Arboretum, Gloucestershire.


'Aucubifolium'

RHS Hardiness Rating: H7

A green leaved form with leaves dotted golden throughout, appearing somewhat similar in this respect to the commonly cultivated form of Aucuba japonica (Bean 1976; van Gelderen et al. 1994). It arose among seedlings at Little and Ballantyne nurseries, Carlisle in around 1876 and described by Nicholson in 1881 (Bean 1976; van Gelderen et al. 1994). ‘Bicolor’ was a similar selection, named five years previously by Späth, though now unknown (van Gelderen et al. 1994).


'Brilliantissimum'

Awards
Award of Merit; Award of Garden Merit; First Class Certificate

RHS Hardiness Rating: H7

Originating at Magdelen College, Oxford (B. Jones, pers. comm. 2020), ‘Brilliantissimum’ has been cultivated in Europe since 1905 and North America since 1927 (Jacobson 1996). It is undoubtedly at its best in spring, when its leaves emerge salmon pink to orange, eventually fading to green. It is slow growing, eventually making a small tree with a rounded crown (Jacobson 1996; Dirr & Warren 2019). Somewhat prone to sunburn (van Gelderen et al. 1994), Dirr & Warren (2019, p. 99) describe it as ‘an absolute knockout in early spring’. It is comparable to ‘Prinz Handjery’.


'Corstorphinense'

Synonyms
'Lutescens Novum'
'Scoticum'

RHS Hardiness Rating: H7

The original Corstorphine sycamore was reputedly one of Edinburgh’s finest living landmarks for centuries. It was thought to have been planted in around 1600, perhaps as part of an avenue that led to Corstorphine Castle, where it persisted until 2005, having been heavily reduced at 8:10 pm on Boxing Day 1998 in a gale (Rodger et al. 2006). In between times, it saw the murder of the second Lord Forrester, James Baillie on 26th August 1679, killed with his own sword by his lover, Christian Nimmo, who also happened to be his wife’s sister (Rodger et al. 2006; Edwards & Marshall (eds) 2019). She was later executed for the deed and their ghosts were said to haunt the tree (Edwards & Marshall (eds) 2019). Lord Forrester is thought to have buried treasure beneath the tree and it was presumably the voice of his ghost that, legend has it, warned villagers to stop digging for it (Rodger et al. 2006). Artefacts made from the timber of the tree include a violin made by renowned maker Colin Adamson (Rodger et al. 2006).

‘Corstorphinense’ was described by Sutherland in 1883, and named after the suburb of Edinburgh in which it grew. It’s leaves are yellow in spring, turning to pale green later on. It has no autumn colour of note but drops its leaves somewhat earlier than other selections of the species (le Hardÿ de Beaulieu 2003). It makes a fine parkland tree, as observable at Westonbirt Arboretum, Gloucestershire.


'Euchlorum'

A fast growing form with large, dark green leaves and large fruit, ‘Euchlorum’ was introduced by Späth’s nurseries in 1878 (Bean 1976). It was first recorded in North America around 1897. The specimen at Bergholt Place, Suffolk mentioned by Bean (1976) and van Gelderen et al. (1994) is described as the only plant known by Jacobson (1996).


f. erythrocarpum (Carr.) Pax

RHS Hardiness Rating: H7

Recorded from the Bavarian Alps in the 19th century, but likely present elsewhere, f. erythrocarpum has distinctly red fruits (Bean 1976). It was also named as a cultivar, from a tree in the nursery of S. Vaillant, France, in 1927 (van Gelderen & van Gelderen 1999), though given its presence in nature, the rank of forma is more apt than treating it as a cultivar. It should be mentioned that trees growing in the British countryside intermittently produce strikingly red fruits, so the validity of this form may be somewhat dubious. A superior clone with fruits consistently red ought to be given an unambiguous name.


f. variegatum (West.) Rehd

Synonyms
Acer pseudoplatanus 'Argenteovariegatum'
Acer pseudoplatanus 'Albo-variegatum'
Acer pseudoplatanus 'Rosea'
Acer pseudoplatanus 'Rubicundum'

Leaves blotched, or blotched and striped with yellow and white (Bean 1976)

RHS Hardiness Rating: H7

Variegated forms of the species have been reported both from the wild and seedbeds (van Gelderen et al. 1994). Known since the early eighteenth century, variegated clones have since been named as cultivars. Plants sold by nurseries in the late eighteenth and early nineteenth centuries under names including ‘albo-variegatum’ “foliis variegatis” and “variegatum” are thought to have been seedlings that arose (Bean 1976). Trees attain similar dimensions to those of the typical form.


'Leopoldii'

Common Names

Synonyms
Acer pseudoplatanus 'Variegatum'

Awards
First Class Certificate

RHS Hardiness Rating: H7

Originating in Belgium and named for King Leopold I by Vervaene in 1864, ‘Leopoldii’ has leaves that are pinkish when young, green with yellow and white mottling later (van Gelderen et al. 1994). Seedlings should not be confused with the authentic selection. forms sold as ‘Variegatum’ are usually this selection, listed here in synonymy.


'Prinz Handjery'

Awards
First Class Certificate

RHS Hardiness Rating: H7

Introduced by Späth’s nurseries in 1883 or earlier, ‘Prinz Handjery’ has leaves that emerge salmon pink, turning pink then light green (van Gelderen et al. 1994). Its lower leaf surcaces are also purple (van Gelderen et al. 1994). It is similar to ‘Brilliantissimum’, which lacks purple leaf undersides, though is reportedly slightly less prone to sunburn and grows slightly larger (Dirr & Warren 2019). It forms a dense shrub to 5 m tall when grafted at the base (van Gelderen et al. 1994; van Gelderen & van Gelderen 1999).


var. tomentosum Tausch

Synonyms
Acer pseudoplatanus var. villosum Parl

Leaves pubescent beneath, with margins more coarsely toothed than the typical variety (Bean 1976; van Gelderen et al. 1994).

Distribution

  • Croatia
  • Italy – Southern regions and Sicily

RHS Hardiness Rating: H7

Frequently occuring within its distribution (van Gelderen et al. 1994), the parent plants of WITA 46 and 47, collected in Calabria in 2016, fits here, while also possessing glaucous lower leaf surfaces. The characters of the plants grown from this gathering have not yet been critically appraised.


'Worley'

Common Names
Golden Sycamore

Synonyms
'Worleei'

RHS Hardiness Rating: H7

Named in 1879 and introduced to cultivation by the Hamburg-based Ohlendorff in 1893 according to (van Gelderen et al. 1994), though reportedly in the trade in the United States by 1981 (Jacobson 1996). It has leaves yellow at first, turning to pale green and is described by Bean (1976) as superior to ‘Corstorphinense’. van Gelderen et al. 1994) list numerous miss-spellings of its name. The most frequently encountered is listed in its synonymy above.

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