Acer (Maple) Notes
The maple genus of deciduous flowering trees amounts to over 150 species. Apart from the fossil record, the antiquity of the family is indicated by the variety of sizes, shapes, and colors of the leaves, variety that is unmatched in other families. Different cultivars of a single species can have leaves with no lobes, with five lobes but barely any separation, with five deeply dissected lobes, with five lobes of which each has five big sharp teeth, or with separate leaflets on their own stalks.
Maples are distributed over North America, much of Europe, and East Asia but they can also be found in the southern hemisphere, especially on the islands of Indonesia. Their fall color, celebrated in North America, is limited as regards natural occurrence to those temperate regions where the summer is hot and the winter is severe. But they are widely valued outside their native areas for their appearance, their shade, and the possibilities, to be found among the numerous species, for meeting special conditions.
In our area the tall bigleaf maple (A. macrophyllum) is a familiar sight in the Santa Cruz Mountains in fall, when the large, long-stalked, deeply cut, lobed leaves turn pale yellow. The leaves are borne in opposite pairs, and attach to the branch without stipules, as with all maples. Its habitat reaches to the Sierra Nevada foothills and to Alaska. It is exceptional among Western hardwoods in being suited for lumbering.
The most distinctive feature of maples is the fruit; it consists of winged seeds, joined together in pairs. A winged seed is called a samara, which is Latin for an elm seed, but the maple seed is winged on one side only. Maple fruits are commonly called keys, in reference to the shape of the keys used for winding up clocks and toys and opening sardine tins.
If you had never seen a maple key falling you might look at one and wonder whether it would settle serenely, tumble, or dive like a hawk. The flowers, forming in late spring, are bunched in various ways according to the species, may be hanging or erect, and may be male, or female, or both. Though the flowers are not striking in appearance, it is interesting to examine them closely and try to explain the differences. The presence of five tiny petals and the provision of nectar suggest pollination by bees, but absence of both these features, as with the box elder (A. negundo), indicates wind pollination.
Adoption of the maple leaf for the Canadian flag seemed an odd selection, given that maples are ubiquitous in North America. The Canada goose must have been considered, though of course that symbol also is shared by the places where the geese go in winter.
Discarded pallets collected by campus residents are often of pine, but occasionally small pieces of quality hardwoods such as oak, sweet gum, or maple can be rescued for small craft projects – it depends on where the original point of shipment was. Asian longhorned beetles got at the maples in Brooklyn in 1996, and by 2002 some 700 trees had been removed as a precaution; the most sensitive target is Central Park.
About this Entry: The main text of this entry is from the book Trees of Stanford and Environs, by Ronald Bracewell, published 2005. Family name updated from Aceraceae to Sapindaceae Oct 2017 (SP).