Acer laxiflorum Pax

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Dan Crowley (2020)

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

Genus

Synonyms

  • Acer pectinatum subsp. laxiflorum (Pax) E. Murray
  • Acer laxiflorum var. dolichophyllum W.P. Fang
  • Acer laxiflorum var. integrifolium W.P. Fang
  • Acer laxiflorum var. longilobum Rehder, in part.
  • Acer laxiflorum var. longiphyllum W.P. Fang

Other species in genus

Glossary

pubescence
Hairiness.
section
(sect.) Subdivision of a genus.
subspecies
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.
synonym
(syn.) (botanical) An alternative or former name for a taxon usually considered to be invalid (often given in brackets). Synonyms arise when a taxon has been described more than once (the prior name usually being the one accepted as correct) or if an article of the International Code of Botanical Nomenclature has been contravened requiring the publishing of a new name. Developments in taxonomic thought may be reflected in an increasing list of synonyms as generic or specific concepts change over time.
taxon
(pl. taxa) Group of organisms sharing the same taxonomic rank (family genus species infraspecific variety).
variety
(var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare minor variants more usefully ranked as forms.

References

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Credits

Dan Crowley (2020)

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

A deciduous tree to 15 m in the wild. Bark dark green with pale stripes. Branchlets glabrous, purplish-red, faintly striped white. Buds stipitate, oblong to ellipsoid, with 2 pairs of valvate scales. Leaves pentagonal, chartaceous, base cordate to subcordate, 3- (rarely 5-) lobed, 7–14 × 5–8 cm, central lobe ovate, triangular-ovate, apex caudate-acuminate, lateral lobes triangular-ovate, apex acuminate; margins double-serrulate, teeth adpressed, upper surface dark green, lower surface paler; petiole 4–7 cm long, green to red, grooved, pubescent or not; autumn colours yellow. Inflorescence terminal, racemose, pendulous, less than 10 flowered, ~4 cm long. Flowers yellowish-green, 5-merous, pedicels slender, sepals oblong, ~0.3 cm long, petals obovate, ~3 cm long, stamens 8, inserted outside the nectar disc. Samaras 2.5–2.7 cm long, wings narrowly spreading to nearly horizontally so. Flowering in May, after the leaves, fruiting in October. (Fang 1939Xu et al. 2008). 

Distribution  China Sichuan, Yunnan

Habitat Temperate mixed forests between 1800 and 2500 m

USDA Hardiness Zone 6-7

RHS Hardiness Rating H6

Conservation status Least concern (LC)

Taxonomic note Treated as a subspecies of Acer pectinatum by van Gelderen et al. (1994), with four apparent varieties (dolichophyllum, integrifolium, longilobum and longiphyllum) all since reduced to synonymy, this taxon sits more comfortably as a separate species as treated by Xu et al. (2008) whose treatment we follow for Trees and Shrubs Online. See also the taxonomic note for A. pectinatum.

Representation of plants attributed to Acer laxiflorum in collections has increased somewhat since Bean (1976a), thanks in part, to the successful SICH expeditions, which introduced greater diversity of a range of Chinese Acer taxa over the course of the nine expeditions (Kirkham 2013). New material has not, however, resolved the confusion around this taxon’s relationship with Acer forrestii (A. pectinatum subsp. forrestii sensu van Gelderen et al. (1994)), as summarised in the account of that species. Suffice to say here that confusion between the two taxa remains, with at least as much material in collections not conforming to the description of one or the other, as that which does. While Xu et al. (2008) use flower number as a character to help distinguish between them, as with other taxa in the section this is proved by cultivated material to be a problematic character.

In cultivation trees of Acer pectinatum (sensu Xu et al. 2008) are easily separated from A. laxiflorum and its affinities by their bark, which soon turns brown with age (see also the account for A. pectinatum). van Gelderen et al. (1994) recognised four varieties within A. laxiflorum, all since reduced to synonymy by Xu et al. (2008). These were distinguished based on inconsequential variations of lobing and pubescence in the leaves. Crucially, however, in relation to cultivated material, when assigning specimens to his earlier variety longilobum (now a synonym of A. pectinatum subsp. taronense), Rehder (1933) excluded W 4108, which he transferred to typical A. laxiflorum. However, this detail was seemingly overlooked by van Gelderen et al. (1994), who did not mention Redher’s distinction, an error hitherto not picked up by all who grow this collection, which may consequently be found growing as A. pectinatum subsp. taronense, rather than A. laxiflorum.

Originally introduced in 1908 by Wilson (Harris 2000), trees of A. laxiflorum mentioned by Bean (1976a) at Trewithen, Cornwall, are still alive and were in good health in May 2019. The SICH introductions include SICH 25, which grows strongly at the David C. Lam Asian Garden, Vancouver, though it is otherwise absent from collections surveyed for SICH material by Charles Erskine in 2013 (Erskine 2012). SICH 0303 and 2114 grow at Quarryhill Botanical Garden, California, the latter also represented at Royal Botanic Gardens, Kew and elsewhere. Specimens of SICH 2448 include two at Windsor Great Park, one of which is forming a multistemmed plant in the Valley Gardens, with graceful arching branches.

Regarding W 4108, of which repropagated material grows at Windsor, the Royal Botanic Garden Edinburgh and Royal Botanic Gardens, Kew, Bean (1976a p. 207) states that ‘the leaves on the extension growths and young spurs are strongly three-lobed; on older, branched spurs they are less lobed but always strongly three-veined. The difference between this and the Trewithen trees is very striking, but it would appear to belong to A. laxiflorum as at present understood’. Variation of this sort is also a feature of other plants attributed to both A. laxiflorum and A. forrestii, further supporting the need for molecular work on the section.

A further source of confusion among cultivated plants is material introduced by a German nursery as Acer laxiflorum (under A. pectinatum subsp. laxiflorum) and apparently frequently planted in continental European collections in the 1990s. This in fact belongs to A. capillipes van Gelderen et al. (1994). Whether this inaccuracy has been addressed in collections of mainland Europe is uncertain, though it seems likely that it has persisted at least here and there, but it has not been observed in British or North American collections.

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