Acer opalus Mill.

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Credits

Dan Crowley (2020)

Recommended citation
Crowley, D. (2020), 'Acer opalus' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-opalus/). Accessed 2020-02-29.

Genus

  • Acer
  • Sect. Acer ser. Monspessulana

Common Names

  • Italian Maple

Synonyms

  • Acer italum Lauth
  • A. montanum Dalechamps ex Lamarck
  • A. opulifolium Vill.
  • A. vernum Carriere ex Lamarck
  • A. rotundifolium Lamarck
  • A. apolifolium Persoon
  • A. opulifolium var. opalus (Miller) Koch
  • A. italicum Lauche
  • A. rupicolum Chabert

Infraspecifics

Other species in genus

Glossary

glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
pendent
Hanging.

References

There are currently no active references in this article.

Credits

Dan Crowley (2020)

Recommended citation
Crowley, D. (2020), 'Acer opalus' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-opalus/). Accessed 2020-02-29.

A deciduous tree to 28 m in the wild. Bark grey, turning pale brown to orange grey and broadly plated, sometimes flaking with age. Branchlets stout, glabrous, reddish brown. Buds ovoid, with many pairs of imbricate scales, brown. Leaves chartaceous to subcoriaceous, broadly pentagonal in outline, base cordate, (three-) five-lobed, 7–12 × 8–16 cm, lobes shallow, ovate, lateral lobes spreading, basal lobes smaller, apex acute to acuminate, margins entire to remotely serrate, upper surface mid to dark green, lower surface paler, pubescent or not, often along veins but soon glabrous, or persistently villose; petiole 7–18 cm long, green or red, faintly grooved and broadening towards the base; autumn colours yellow to brown. Inflorescence terminal, umbellate, pubescent at first, pendulous, 6–16 flowered, 8–15 cm long. Flowers yellow, 5-merous, sepals ovate, 0.6 cm long, petals narrow-oblong, 0.5 cm long, stamens 10–12, inserted inside the nectar disc. Samaras to 2.5–5 cm long, wings spreading variously; nutlets rounded. Flowering March to April, before or with the leaves, fruiting in September to October. (van Gelderen et al. 1994le Hardÿ de Beaulieu 2003Gregory 2019)

Distribution  AlbaniaAlgeriaCroatiaFranceGermanyGreeceHungaryItalyMontenegroMoroccoSerbiaSloveniaSpainSwitzerland

Habitat Cool areas in humid forests, often on limestone, up to 2100 m asl.

USDA Hardiness Zone 5-6

RHS Hardiness Rating H6

Awards Award of Merit

Conservation status Least concern (LC)

A tree 30 to 65 ft high, of rounded habit, sometimes much smaller or even bushy; branchlets glabrous. Leaves 212 to 412 in. wide, somewhat less in length, shallowly five-lobed, heart-shaped at the base, irregularly toothed; dark green, glossy and glabrous above, paler and more or less downy beneath, especially along the chief veins and in their axils, occasionally quite glabrous; lobes angular. Flowers yellow, appearing in March, numerously crowded in short-stalked corymbs; each flower on a slender, glabrous, pendent stalk, 1 to 112 in. long. Fruit glabrous; keys 1 to 112 in. long; wings 25 in. wide, varying considerably in divergence.

Native of S. and Central Europe; introduced in 1752. It is one of the most ornamental of early-flowering trees, producing its blossoms regularly and in great abundance in March and April; they are of a clearer and more pronounced yellow than in most maples. There are several good specimens at Kew, the largest 50 × 6 ft (1965). At Westonbirt there are two off the Broad Drive, 60 × 712 and 53 × 412 ft (1966). There is much confusion in the nomenclature of this maple. It is very variable and some authorities have separated the following varieties from it as distinct species:

From the Supplement (Vol. V)

specimens: Kew, 62 × 634 ft (1979); St James’s Park, London, 41 × 412 ft (1982); Grayswood Hill, Haslemere, Surrey, 62 × 914 ft (1982); Westonbirt, Glos., Broad Drive, 75 × 814 ft (1982) and, Willesley Drive, 80 × 7 ft (1982); Balloan, Castletown, I.o.M., 74 × 1012 ft (1978).

var. obtusatum – The examples at Kew measure 62 × 1014 ft at 3 ft (1984) and 41 × 514 ft (1980).

var. tomentosum – The tree at Westonbirt measures 68 × 7 ft (1976).

The two above varieties are by some authorities treated as species distinct from A. opalus under the respective names A. obtusatum and A. neapolitanum. They differ clearly enough from typical A. opalus, but it is questionable whether they are really separable from each other.


subsp. obtusatum (Willd.) Gams

Common Names
Balkan Maple

Synonyms
A. obtusatum Willd
A. aetnense Tineo ex Strobl.
A. neopolitanum Tenore
A. opalus var. obtusatum (Willd.) Henry
A. opulifolium var. tomentosum Tausch
A. opulifolium var. velutinum Boissier non A. velutinum Boisser
A. italum var. neopolitanum (Tenore) Dieck

Subsp. obtusatum has obtuse lobe tips and persistently pubescent lower leaf surfaces (Crowley 2018). 

Distribution

  • Algeria
  • Bosnia and Herzegovina
  • Croatia
  • France
  • Italy
  • Macedonia
  • Montenegro
  • Serbia
  • Slovenia

RHS Hardiness Rating: H6

Leaves on the whole larger than in the type, and up to 5{1/2} in. wide, the lobes more rounded and the whole under-surface covered with a close down; flower-stalks hairy; fruit-wings not so large as in var. tomentosum. Native of Central and E. Europe. There is an old specimen at Kew 48 ft high, on a trunk measuring 9 ft in girth at 3 ft.

var. tomentosum (Tausch) Rehd.

Synonyms
A. opulifolium var. tomentosum Tausch
A. neapolitanum Ten.
A. opalus var. neapolitanum (Ten.) Henry

Leaves up to 6 or 7 in. wide, covered with a pale felt beneath, the lobes quite shallow, especially the basal ones. Flower-stalks hairy, remaining so until the fruits ripen. Native of the country about Naples, where, like the type farther north in Italy, it is largely employed in vineyards as a support on which to train the vines. There is an example of this variety at Westonbirt, off the Broad Drive, measuring 64 × 6{1/2} ft (1966).

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