Big-Tooth Aspen
Populus grandidentata
Willow family (Salicaceae)

Description: This tree becomes 50-80' tall at maturity, forming a long straight trunk up to 3' across and an open crown with ascending branches. Trunk bark is orange-tinted white to gray and relatively smooth, although the trunk bark of old trees is more furrowed, rough-textured, and gray-brown. Branch bark is gray to nearly white and smooth, while twigs are light gray to orange-brown and glabrous. Alternate deciduous leaves about 3-4" long and 2-3" across occur along the twigs and young shoots; they are oval in shape and coarsely crenate-dentate along their margins. There are typically 5-15 large teeth with blunt tips on each side of the leaf. The upper leaf surface is medium green and glabrous, while the lower leaf surface is light to medium green and glabrous to sparsely pubescent. However, young leaves, as they emerge during the spring, are densely covered with white silky hairs; these hairs soon fade away as the season progresses. The flattened petioles are 2-4" long, light green or grayish green, and glabrous to pubescent.

Big-Tooth Aspen is dioecious, developing male (staminate) and female (pistillate) flowers on separate trees. Male flowers are produced in drooping catkins about 2-4" long. Each male flower (about 1/8" or 3 mm. across) has a short disk at its base with about 12 stamens; each male flower is also accompanied by a bract that is deeply cleft into narrow ciliate lobes. Female flowers are produced in spreading or drooping catkins about 1-3" long. Each female flower (about 1/8" or 3 mm. across) has a short disk at its base and a conic-lanceoloid ovary. At the apex of each ovary, there is a pair of stigmata; each stigma is deeply bifurcated. Each female flower is accompanied by a bract that is deeply cleft into narrow ciliate lobes. The blooming period occurs during mid-spring for 1-2 weeks; the flowers are cross-pollinated by the wind. Afterwards, the female catkins become slightly longer and the female flowers are replaced by conic-lanceoloid seed capsules up to " long. Each of these capsules divides into 2 parts to release several tiny seeds that are embedded in tufts of fine white hair. The seeds are distributed by the wind. The woody root system is shallow and widely spreading; it often forms clonal trees from underground runners. The leaves of immature clonal trees tend to be larger in size and less prominently toothed than those of a mature tree. The deciduous leaves become pale yellow during the autumn.

Cultivation: The preference is full sun, moist well-drained conditions, and sandy loam. However, partial sun, drier conditions, and other soil types are also tolerated. This tree develops quickly and may live up to 100 years. In some situations, it can spread aggressively by developing clonal trees from underground runners.

Range & Habitat: The native Big-Tooth Aspen occurs occasionally in northern and east-central Illinois; elsewhere in the state, it is uncommon or absent. Illinois lies along the southern range-limit for this species. Habitats consist of upland woodlands and sandy woodlands, typical savannas and sandy savannas, disturbed open woodlands, riverbanks, and abandoned fields. Big-Toothed Aspen is a pioneer species that prefers disturbed areas that are not too shady. Mature trees are easily damaged by wildfires because of their thin bark. Nonetheless, Big-Toothed Aspen can rapidly spread after a wildfire because clonal trees soon develop from underground runners.

Faunal Associations: Big-Toothed Aspen and other Populus spp. are hosts to many kinds of insects. The foliage of these trees is eaten by caterpillars of the skipper Erynnis icelus (Dreamy Duskywing) and caterpillars of the butterflies Limenitis archippus (Viceroy), Limenitis arthemis arthemis (White Admiral), Limenitis arthemis astyanax (Red-Spotted Purple), and Nymphalis vau-album j-album (Compton Tortoiseshell). The caterpillars of Protitame virginalis (Virgin Moth) and other moths also feed on these trees (see Moth Table). Other insect feeders include larvae of the sawfly Trichosoma triangulum, the leafhoppers Idiocerus lunatus and Kybos copula, the plant bug Tropidosteptes populi, Aphis maculatae (Spotted Poplar Aphid), Chaitophorus populifolii (Poplar Leaf Aphid), Pterocomma smithiae (Black Willow Aphid), and Thecabius populiconduplifolius (Folded-Leaf Poplar Aphid). The larvae of several long-horned beetles bore through the wood of these trees; these species include Anoplophora glabripennis (Asian Long-Horned Beetle), Oberea delongi (Poplar-Twig Borer), Oberea schaumi (Poplar-Branch Borer), Saperda calcarata (Poplar Borer), and Saperda inornata (Poplar-Gall Saperda). The following leaf beetles have been observed to feed on Big-Toothed Aspen: Chrysomela crotchi, Chrysomela knabi, Chrysomela laurentia, Chrysomela lineatopunctata, Chrysomela scripta, Crepidodera populivora, Crepidodera solita, Phratora purpurea, Tricholochmaea decora, and Zeugophora scutellaris (see Clark et al., 2004). Among vertebrate animals, the Ruffed Grouse and Greater Prairie Chicken feed on the buds and catkins; the buds are also eaten by the Purple Finch, Fox Squirrel, and Red Squirrel. Twigs and foliage are a source of food for White-Tailed Deer and Elk; the Cottontail Rabbit and Meadow Vole gnaw on the bark of saplings and young clonal sprouts during the winter. When Big-Toothed Aspen grows along rivers, its bark and wood are a source of food to the Beaver, while its branches are used as construction material for the lodges and dams of this animal. As this tree becomes older, it often forms cavities that are used as nesting habitat by the Red-Breasted Nuthatch, owls, and woodpeckers, while other birds nest along its branches. Tree squirrels and other mammals also use the cavities as dens.

Photographic Location: A deciduous woodland in Fayette County, Illinois. The photographs were taken by Keith & Patty Horn (Copyright 2010).

Comments: Big-Toothed Aspen is similar to Quaking Aspen (Populus tremuloides), except the latter has slightly smaller leaves (2-3" long) with more abundant smaller teeth (about 25 per side). It also resembles the more common Eastern Cottonwood (Populus deltoides), except the latter has leaves with truncate bottoms and more abundant smaller teeth. All three of these species have leaves with flattened petioles, which causes them to flutter in response to even a weak breeze. With the exception of the introduced Populus nigra italica (Lombardy Poplar), other Populus spp. in Illinois have leaves with round petioles. Occasionally, Big-Toothed Aspen and Quaking Aspen hybridize, which has been named Populus smithii. This hybrid tends to have leaves with more teeth than those of Big-Toothed Aspen, but fewer teeth than those of Quaking Aspen.