Acer shirasawanum (Shirasawa's Maple or Fullmoon Maple; Japanese: オオイタヤメイゲツ ooitayameigetsu) is a species of maple native to Japan, on central and southern Honshū (Fukushima Prefecture southwards), Shikoku, and Kyūshū.
It is a deciduous large shrub or small tree growing to 8–15 m tall with a trunk up to 50 cm diameter. The bark is smooth on both young and old trees. The shoots are slender, and hairless. The leaves are rounded, 4.5–8 cm long and 6–12 cm broad, palmately veined and lobed, with 9–13 (rarely 7) serrate shallowly incised lobes; they are hairless, or thinly hairy at first with white hairs; the petiole is 3–7 cm long and hairless. In autumn, the leaves turn bright gold or orange to dark red. The flowers are 1 cm diameter, with five dark purplish-red sepals, five small whitish petals (soon lost), and red stamens; they are andromonoecious, with inflorescences containing flowers with either both sexes, or just male, and are produced 10–20 together in erect terminal corymbs in early spring soon after the leaves appear. The fruit is a paired samara with the nutlets 5–10 mm diameter with a 20–25 mm wing, erect above the leaves, bright red maturing brown.
- Acer shirasawanum subsp. shirasawanum
- Acer shirasawanum subsp. tenuifolium
Synonyms include Acer japonicum var. microphyllum Siesmayer and Acer japonicum subsp. shirasawanum.
Cultivation and uses
It is grown as an ornamental tree in gardens for its foliage and autumn colour, but is seen far less commonly than Acer palmatum (Japanese Maple). A number of cultivars have been selected; the lighter-coloured A. shirasawanum cultivar 'Aureum' is very widely grown, much more common in cultivation than the main species, and has gained the Royal Horticultural Society's Award of Garden Merit.
- Okayama science university: Acer shirasawanum (in Japanese; google translation)
- Okayama science university: Acer shirasawanum flowers (in Japanese; google translation)
- Rushforth, K. (1999). Trees of Britain and Europe. Collins ISBN 0-00-220013-9.
- Kanagawa Prefecture trees and shrubs: Acer sieboldianum (in Japanese; google translation). Archived 2009-10-24.
- Infoseek Japan: Maples (in Japanese; google translation)
- Maples for Gardens: A Color Encyclopedia by C.J. van Gelderen & D.M. van Gelderen, 1999
- Delendick, T. J. (1984). Reconsideration of Two Infraspecific Taxa of the Fullmoon Maple, Acer japonicum (Aceraceae). Brittonia 36 (1): 49-58 doi=10.2307/2806291
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