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Published In: Arbustrum Americanum 4. 1785. (Arbust. Amer.) Name publication detailView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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5. Acer saccharum Marshall (sugar maple, hard maple)

Pl. 196 m–o; Map 808

Plants monoecious or sometimes dioecious, medium to large trees to 30 m tall with ascending to spreading branches, the bark of young trees smooth and gray to dark brown, becoming furrowed and/or separated into narrow, thick plates on older trees. Twigs gray to reddish- to orangish brown, the winter buds elliptic-ovate, sharply pointed at the tip, with 6–12 overlapping scales. Leaf blades 7–15 cm long, broadly triangular-ovate in outline, sometimes wider than long, the undersurface light green and sometimes glaucous, glabrous, or often with minute tufts of hairs in the axils of the main veins, less commonly hairy on the surface or along the veins, with (3)5 main lobes, these tapered to sharply pointed tips and with the sinuses rounded or U-shaped, the margins undulate or more commonly toothed and with smaller lobes, the central lobe cut 1/3–1/2 of the way to the blade base, broadest at the base or with nearly parallel sides. Inflorescences produced during expansion of the leaves, umbellate staminate and pistillate clusters from buds at or near the branch tips, the individual flowers with long, drooping, hairy stalks. Calyces 2.5–6.0 mm long, the sepals fused more than 1/2 of the way to the tip, with 5 shallow lobes, greenish yellow, usually hairy toward the tips. Corollas absent. Staminate flowers with 5–8 stamens inserted on the margin of a nectar disk. Pistillate flowers with the ovary glabrous or nearly so. Fruits dispersing after the leaves are mature, the samaras 2.5–4.0 cm long, glabrous, the wings 2.0–3.5 cm long, spreading at about 90–120° (rarely much narrower and nearly parallel). 2n=26. April–May.

Common throughout Missouri (eastern U.S. west locally to Idaho and Arizona; Canada, Mexico). Mesic to dry upland forests, margins of glades, ledges and bases of bluffs, and banks of streams, rarely bottomland forests; also moist to dry, shaded, disturbed areas.

This species is a major timber tree in the eastern United States. However, as noted by Settergren and McDermott (1962), most of the “hard maple” that is sold in Missouri (principally as veneers and boards for flooring) is imported from elsewhere, because Missouri sugar maples tend to have unsightly discolorations in their wood. The species is the principal source of maple syrup and also is cultivated as a shade tree. The leaves turn various shades of yellow, orange, and red in the autumn.

The A. saccharum complex consists of a bewildering assortment of names and taxa, many of which have been treated as separate species at different times in the past. It is possible that this is an example of a species whose distribution became fragmented at some point in the past (perhaps in response to glaciation), with subsequent morphological divergence of geographically isolated groups of populations over time. These segregates then presumably came into contact again and hybridized as secondary hardwood forests developed following the rapid destruction of primary forests in the eastern United States for agriculture and logging during the past two centuries. The present treatment follows that of Desmarais (1952), whose detailed study of morphological variation provides a good starting point for further investigations into interrelationships among taxa in the group. Readers should note that there is marked intergradation between the four subspecies recognized below.

The analysis of Desmarais (1952) is notable for documenting the large range of specimens that are intermediate between the black and sugar maple morphotypes, which many botanists continue to treat as distinct species. Regional floras of midwestern states, including Voss (1985) and the present volume, also have noted the existence of large numbers of sugar maple trees with at least some black maple characteristics. In addition to morphological features, such trees seem to combine the faster growth rate of sugar maple with the greater drought resistance of black maples. The decline of oak regeneration and concomitant invasion of the oak-hickory-dominated forests by sugar maples in Missouri has been of grave concern to foresters and ecologists (Wuenscher and Valiunas, 1967; Nigh et al., 1985; Pallardy et al., 1988, 1991). It has been attributed to fire suppression following European settlement of the region that promoted succession to a more mesic forest type. It also may have been aided by the ecological adaptations of sugar maple stocks potentially containing genetic materials of black maples conferring greater drought resistance on such trees.

 

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1 1. Leaf blades 310 cm long, the lobes blunt to rounded at the tips; ovary and young fruit hairy (becoming nearly glabrous at maturity); bark light gray, smooth, becoming shallowly furrowed and sometimes with scaly ridges on older trees ... 5A. SSP. FLORIDANUM

Acer saccharum subsp. floridanum
2 1. Leaf blades 615 cm long, the lobes tapered to sharply pointed tips (sometimes bluntly pointed in ssp. schneckii); ovary and fruit glabrous; bark gray to dark gray or brown, somewhat roughened, becoming deeply furrowed and sometimes with peeling ridges on older trees

3 2. Leaf blades with the undersurface yellowish green to green; sinuses between the main leaf lobes mostly forming angles of greater than 90° ... 5B. SSP. NIGRUM

Acer saccharum subsp. nigrum
4 2. Leaf blades with the undersurface pale green, bluish green, grayish green, or whitish, sometimes glaucous; sinuses between the main leaf lobes mostly forming angles of less than 90°

5 3. Lower surface of the leaf blades glabrous or hairy, the lobes tapered to sharply pointed tips and often with secondary lobes or teeth ... 5C. SSP. SACCHARUM

Acer saccharum subsp. saccharum
6 3. Lower surface of the leaf blades hairy along the veins, the lobes tapered but bluntly pointed or rounded at the tips, usually lacking or with very few secondary lobes or teeth ... 5D. SSP. SCHNECKII Acer saccharum var. schenckii
 


 

 
 
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