Acer grandidentatum Nutt.

The westernmost representative of the sugar maple complex, Acer grandidentatum is a species of interior western North America, extending from the eastern Rockies east to Texas, where its var. sinuosum occurs. The species has also been suggested as a parent of the Caddo sugar maples of Oklahoma (though see the account for A. saccharum). While it varies in leaf size and coloration, in its typical form it is separated from other sugar maples by its usually multi-stemmed or shrubby form, leaves often somewhat leathery with rounded lobes, the central lobe more deeply cut and narrowest at its base (Grimshaw & Bayton 2009). Its epithet, grandidentatum, refers to the large teeth typical of the leaves.

As with other members of the sugar maple complex, the species is of greatest significance within its native range, and a number of cultivars are readily available in North America. Though slow growing, it is tolerant of drought, cold, rapid changes in temperature and drying winds, though will not succeed in overly wet conditions (Dirr & Warren 2019). The species is becoming more important in urban conditions in the southwestern United States where it is valued for its autumn colour, which compares to that of typical A. saccharum (Kuhns 2003), though varies within populations and in response to environmental conditions (Kuhns 2003; Dirr & Warren 2019). Relatively untroubled by pests and diseases, its overall toughness is appreciated by those attempting to grow trees in more challenging situations.

The first material grown in Britain is thought to have been that at RBG Kew received from Charles Sargent in 1885 (Bean 1976), of which a single plant remains. It is now present in several other specialist UK collections, with a plant from seed collected by Hugh Angus (NATEX 10) in the Big Bend National Park, Texas, proving slow growing at Westonbirt, standing at 2.5 m tall in January 2024 (pers. obs). At Rogów, Poland, it is also slow growing; one specimen here, of Cochise County, Arizona provenance, dating from 1979, was frozen to the ground during very cold winter 1986–87. Though it survived, it has since attained only about 2 m in height (P. Banaszczak pers. comm. 2023).