Acer saccharum Marsh.

(Sect. Acer, Sect. Saccharodendron)

Common names

Sugar Maple

Synonyms

A. saccharinum Wangenh., not L.

Article sources

Bean

New Trees

A deciduous tree over 100 ft high in a wild state, with a trunk 9 to 12 ft in girth, forming a shapely rounded head of branches; branchlets glabrous. Leaves palmate, usually five-lobed, heart-shaped at the base, 4 to 6 in. wide; always downy in the axils of the chief veins beneath, but varying in different trees from glabrous to downy in other parts. Flowers without petals, greenish yellow, produced in clusters, each flower on a thread-like, hairy stalk more than 2 in. long. Fruit glabrous, wings 1 in. long, 38 in. wide.

Native of eastern N. America; introduced, according to Aiton, in 1735, but not many fine specimens are to be found in this country. The most notable arc in the Westonbirt collection, the finest there, and perhaps in the country, being in the Park, near the lodge, measuring 80 × 8 ft (1966). Others at Westonbirt are: Willesley Drive 70 × 434 ft; Circular Drive 63 × 534 and 65 × 434 ft (1966). In the grounds of Blenheim Palace, Oxon., there is a tree of 64 × 514 ft (1965). In Ireland the best recorded is at Mount Usher, Co. Wicklow, Eire, 62 × 714 ft (1966). In leaf, the sugar maple, especially in its more glabrous form, bears some resemblance to the Norway maple; but the sap of the sugar maple is watery, not milky as in the other.

The famous maple sugar of N. America is obtained almost solely from the sap of this tree. The State of Massachusetts alone used to supply more than half a million pounds annually. It is obtained by tapping the trees and collecting the juice, which is afterwards evaporated. As an ornamental tree in England this maple never seems to have been a great success, and although it appears to be quite hardy, does not grow quickly when young. In streets, and isolated in the meadows of New England, it is magnificent, and forms one of the chief elements in the glorious colour effects of autumn there, its leaves dying off into various shades of orange, gold, scarlet, and crimson, each tree, according to Emerson, retaining year after year its particular shades.

var. rugelii (Pax) Rehd. A. rugelii Pax – A large tree with thin, three-lobed leaves; the lobes usually entire, triangular, pointed; lower surface rather glaucous and downy. Found wild from N. Carolina and Georgia to Missouri, being the common form of sugar maple in that region. The lower branches often bear leaves identical with those of the type. Introduced to Kew in 1908.

cv. 'Temple's Upright'. – A very striking form with a narrow columnar habit. Once known as A. saccharum monumentale.

A. barbatum Michx. – This species, known as the southern sugar maple, takes the place of A. saccharum in the coastal plain, from Virginia to Texas. It makes a smaller tree with a paler bark; leaves smaller, to 3 in. wide, usually downy beneath; lobes with entire or undulate margins. The name A. floridanum Pax has also been used for this species. It is in cultivation at the Glasnevin Botanic Garden, where there is a tree 25 ft high.

A. nigrum Michx. f. A. saccharum var. nigrum (Michx. f.) Britt. – Another close ally of the sugar maple, known as the black maple, and found growing with it in the northern states of eastern and central U.S.A. The marks of distinction are the darker, more furrowed bark, the darker and duller green leaves with rather drooping sides, and the shallower, more rounded toothing of the lobes. According to Sargent it may be distinguished at all seasons by the orange colour of the branchlets.

A. leucoderme Small A. saccharum var. leucoderme (Small) Sarg. – A small shrubby tree, rarely more than 25 ft high, with a pale grey or chalky white bark. It is closely allied to the sugar maple but comes from further south, being commonest, according to Sargent, in the more northern parts of Georgia and Alabama. Leaves three- or five-lobed, 2 to 312 in. long and wide, the lobes triangular, with usually two large teeth; the base truncate or slightly heart-shaped; lower surface covered with whitish velvety down, especially where the five veins meet the leaf-stalk, which is glabrous. Introduced to Kew in 1902, when seed was received from Prof. Sargent. The specimen now in the collection measures 28 × 134 ft (1960). There is one at Westonbirt, Glos., measuring 51 × 234 ft (1967).


From the Supplement (Vol. V)

specimens: Hackwood Park, Hants, 80 × 812 ft (1977); Belton Park, Lincs., 68 × 8 ft (1978); Blenheim Palace, Oxon., 62 × 614 ft (1978); Bulstrode Park, Oxon., 90 × 11 ft (1967); Westonbirt, Glos., Willesley Drive, 88 × 512 ft, Broad Drive (NW), 82 × 534 ft (1982); Stratford Park, Glos., 60 × 512 ft (1984); Eastnor Castle, Heref., 50 × 712 ft and 52 × 714 ft (1977); Whiteways, Devon, 79 × 612 ft (1978); Pencarrow, Cornwall, 66 × 4 ft (1978); Mount Usher, Co. Wicklow, Eire, 70 × 734 ft (1975).

The three related species mentioned on page 232 have all been given the rank of subspecies of A. saccharum by Y. Desmarais in Brittonia, Vol. 7, pp. 347-87 (1952), A. barbatum as A. s. subsp. floridanum. The key character he uses to separate A. nigrum (A. s. subsp. nigrum) is that its leaves are yellowish green beneath and usually pubescent with short erect hairs, against glaucous or whitish and usually glabrous beneath in typical A. saccharum. See also E. Murray in Kalmia, Vol.7, pp. 13-19 (1975).

The example of A. nigrum in the Edinburgh Botanic Garden measures 62 × 414 ft (1985).

From New Trees

Acer saccharum Marshall

(Sect. Acer, Ser. Saccharodendron)

Sugar Maple

This species was described by Bean (B231, S60) and Krüssmann (K104), and is an important maple in temperate tree collections and landscapes. Authorities recognise variable numbers of subspecific taxa. Desmarais (1952) constructed a key to six subspecies, though additional taxa are recognised by van Gelderen et al. (1994). Presented below is a key to seven subspecies (devised by Peter Gregory and used with his kind permission), with an indication of the distribution of each from van Gelderen et al. (1994). However, the delimitation of the various subspecies and varieties is complex, as morphological characters vary continuously across the vast range. Most of the A. saccharum subspecies are well known in cultivation, and were described by Bean (1976a) under different names (A. barbatum, A. grandidentatum, A. leucoderme, A. nigrum). Material from the southernmost population, recognised as subsp. skutchii, is new to cultivation and is described below.

Numerous cultivars of A. saccharum have been named, with varying characters useful for different sites and conditions. A summary guide is provided by Dirr (1998).

1a.

Leaf underside pale green to glaucous

2

1b.

Leaf underside yellow-green, lobes shallow, central lobe with divergent margins

6

2a.

Leaves large (≥ 10–15 cm)

3

2b.

Leaves small (5–10 cm)

5

3a.

Leaves deeply lobed, margins of central lobe parallel to inwardly angled

4

3b.

Leaves shallowly lobed, margins of central lobe slightly divergent; USA (Illinois, Indiana, Missouri)

subsp. schneckii

4a.

Lobe tips acute, leaf undersides glabrous to pubescent with silky appressed hairs; widespread in eastern North America (Canada, Mexico, USA)

subsp. saccharum

4b.

Lobe tips bluntly pointed, leaf undersides pubescent and glaucous; Guatemala, Mexico (southern)

subsp. skutchii

5a.

Margins of central lobe parallel to slightly divergent, lobe tips bluntly pointed; Mexico, USA (Florida, Texas)

subsp. floridanum (Chapman) Desmarais

5b.

Margins of central lobe inwardly angled, lobe tips rounded; USA (Oklahoma and Texas to Arizona and Montana, especially Rocky Mts.)

subsp. grandidentatum

6a.

Leaves small (5–10 cm), undersides with soft appressed hairs, bark smooth, pale grey to chalky white; USA (Alabama, Arkansas, Florida, Georgia, Louisiana, N. Carolina, S. Carolina)

subsp. leucoderme (Small) Desmarais

6b.

Leaves large (≥ 10–15 cm), undersides with stiff, short, erect hairs, bark rough, dark grey-brown to black; Canada (Ontario, Quebec), USA (northeast, south to Kentucky, west to Michigan, Iowa, Kansas)

subsp. nigrum

 

Acer saccharum subsp. skutchii (Rehder) A.E. Murray

Subsp. skutchii forms a tree to 20 m tall. Branchlets glabrous. Leaves 12–16 × 14–20 cm, lower surface glaucous with dense tomentum on the veins. Samaras 2.5–4.5 cm long. Van Gelderen et al. 1994. Distribution GUATEMALA; MEXICO. Habitat Cloud forest over limestone. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT106.

This is the southernmost variant of the sugar maples, but its precise delimitation in the western Mexican mountains is not entirely clear (S. Hogan, pers. comm. 2007), as subspp. floridanum, grandidentatum and saccharum also penetrate Mexico (van Gelderen et al. 1994). Material from Tamaulipas in cultivation in the western United States appears to fit subsp. skutchii, and has large leathery leaves that persist into the New Year, when they colour red and fall slightly before or as the new leaves emerge, thus making the tree almost evergreen. At Tregrehan at least it has attractive pinkish spring growth (T. Hudson, pers. comm. 2007). There is a good specimen in the Hogan–Sanderson plantings in Northeast 11th Avenue, Portland, Oregon, and it is grown in the southeastern states from collections made by Yucca Do Nursery. It is rare in Europe, but a few examples are known. Tom Hudson (pers. comm. 2007) planted one in 1995 at Tregrehan but, in the belief that it was tender, put it in a sheltered site where competition from other trees has suppressed it, and it is still only 2 m in 2007. This taxon in fact appears to be extremely hardy, reported to tolerate at least –18 ºC, and to grow well in heavy clay soils (Raulston 1996), although leaves will be lost if temperatures fall below this (Hogan 2008).

Genus

Acer

Other species in the genus