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Dan Crowley (2021)
Crowley, D. (2021), 'Acer rubrum' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous tree to 28 m. Bark grey, smooth when young, turning darker and fissuring longitudinally with age, sometimes developing ridges or plates. Branchlets slender, glabrous or white tomentose, greenish, turning red to reddish brown. Buds ovoid, with four to seven pairs of imbricate scales. Leaves broadly pentagonal in outline, chartaceous to coriaceous, base cordate to cuneate to rounded, unlobed or three to five (-nine) lobed, 5–18 × 2–10 cm, lobes apically acute, margins serrate or double serrate with acute teeth, upper surface light green, lower surface paler or glaucous, glabrous, pubescent or white tomentose; petiole 5–10 cm long, red or green, glabrous, pubescent or white tomentose, often grooved, broadest at base; autumn colours yellow to scarlet. Inflorescence axillary, fasciculate-umbellate, few flowered. Flowers red (rarely yellow), 5-merous, monoecious or dioecious, pedicels long and slender, sepals oblong, obtuse, petals linear to oblong, shorter than sepals, stamens five to eight, inserted in the middle or on outside of the nectar disc. Samaras 1.2 to 3 (–5 cm in var. drummondii) cm long, wings spreading erectly to acutely. Nutlets slightly convex. Flowering January to May, before unfolding leaves, fruiting in late spring to summer (Sargent 1965; (van Gelderen et al. 1994; Rushforth 1999; Lance 2004; Weakley 2012).
Distribution Canada New Brunswick, Ontario, Québec United States Arkansas, Alabama, Connecticut, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Missouri, Mississippi, North Carolina, New Hampshire, New York, Oklahoma, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin
Habitat Mixed deciduous forest and margins of boreal forests. It occurs on both dry and wet sites, along rivers and lakes, in marshes, swamps as well as on sandy plains, dunes and rocky, mountain slopes between 0 and 1370 m asl.
USDA Hardiness Zone 4-10
RHS Hardiness Rating H6
Awards Award of Merit
Conservation status Least concern (LC)
Taxonomic note (Weakley 2012) treats A. rubrum var. drummondii at specific rank, indicating that it is of hybrid origin derived from A. rubrum and A. saccharinum, though this interpretation is not widely accepted and its varietal status is followed here. This author also treats two varieties within A. rubrum: var. rubrum and var. trilobum. The two are separated by degrees of leaf size and lobing, the nominate variety with leaves usually with cordate bases, five lobes and 7–18 cm wide, while those of var. trilobum usually with cuneate to subcordate bases, unlobed to three lobed and 2–10 cm wide. However, intermediate leaf characters are found on plants in cultivation and thus, no attempt has been made to distinguish between the two here.
A deciduous tree, occasionally over 100 ft high in America, with a trunk up to 13 ft in girth; and over 70 ft high in England, forming a rounded head of branches; bark greyish; branchlets glabrous, except when quite young. Leaves three- or five-lobed (the lobes pointed and somewhat triangular, the middle one usually the longest), from 2 to 5 in. wide, and often longer than broad, coarsely and unevenly toothed; upper surface dark green, glabrous, lower one blue-white and more or less downy, especially along the veins. Flowers appearing in March and early April in dense clusters before the leaves, at the joints of the previous year’s wood, or on short spurs of still older wood, rich red, each flower on a reddish stalk at first quite short, but lengthening as the flower and fruit develop. Fruits on slender drooping stalks 2 to 3 in. long; wings about 3⁄4 in. long, 1⁄4 in. wide, dark dull red spreading at about 60°.
Native of eastern N. America, and already in cultivation in England by the middle of the seventeenth century. It is a handsome and fairly common tree. When the first edition of this work was published the largest in the country grew at Bagshot Park, Surrey, which measured 80 × 91⁄2 ft (1907); the tallest there now is 65 × 101⁄2 ft (1960). At Westonbirt there is a specimen of 73 × 43⁄4 ft in Willesley Drive and two others in the collection approaching that size. At Wakehurst Place it is 65 × 61⁄2 ft (1966) and at Kew 52 × 53⁄4 ft (1960). The red maple is represented in the R.H.S. Gardens, Wisley, by an example 45 ft high, near the lake.
There is a considerable resemblance between this tree and A. saccharinum, and they are frequently confused. A. rubrum, however, is more compact and of slower growth; the leaves are not so much or so deeply cut, the down beneath them more fluffy, and the fruits are less than half as large. In the United States this maple produces most beautiful colour effects in autumn, the leaves turning scarlet and yellow. In this country it is not so good, but sometimes the leaves change to bright yellow, or dark brownish red, or occasionally red. It should be planted in a moist position.
specimens: Bagshot Park, Surrey/Berks., 70 × 121⁄4 ft at 3 ft (1982); Wakehurst Place, Sussex, 42 × 71⁄4 ft (1981); Ashburnham Park, Sussex, 58 × 81⁄2 ft (1978); Melbury, Dorset, Pleasure Gardens, 50 × 81⁄2 ft and, Valley, 58 × 73⁄4 ft (1980); Trewidden, Cornwall, 56 × 91⁄4 ft at 3 ft (1979); St Fagans, Cardiff, a fine tree, 77 × 7 ft (1980); Powis Castle, Powys, 58 × 71⁄2 ft (1981).
† cv. ‘Scanlon’. – A selection giving fine autumn colour and with a conical crown that makes it suitable for confined spaces. It is one of the many ‘tailor-made’ trees bred by E. H. Scanlon and Associates at Olmsted Falls, Ohio, USA.
† cv. ‘October Glory’. – A selection for autumn colour, raised in the USA by the Princeton Nurseries.
Cultivars such as the above are preferable to seed-raised trees, which can be very disappointing if autumn colour was hoped for.
A. pycnanthum – This is now in cultivation and growing well.
A. rubrum var. pycnanthum (K. Koch) Mak
A. drummondii Hook & Arn