Aquatic and Wetland Vascular Plants of the Northern Great Plains
21. Salicaceae, the Willow Family
1. Populus L. -- Aspen, cottonwood, poplar1. Populus deltoides Bartr. ex Marsh. -- Cottonwood
Large tree 20-30(40) m tall, with a massive trunk often 1 m or more in diameter, divided into large ascending branches near the base, forming a large rounded crown; bark gray, deeply furrowed; twigs olive-brown to yellowish, turning grayish with age; leaf buds covered by several bud scales, tan, ovoid, very resinous. Leaves light green, deltoid-ovate, mostly 4-10 cm long, 4-11 cm wide, caudate-acuminate at the tip, finely to coarsely crenate-serrate, obtuse to broadly truncate or cordate at the base; petioles flattened at the junction with the blade, 3-10 cm long; stipules minute, caducous. Catkins loosely flowered, pendulous; bracts fimbriate, caducous; flowers subtended by a cup-shaped disk 1.5-4 mm wide; male catkins dark red, soon deciduous; male flowers of (30)40-80 stamens; female catkins greenish, 7-13 cm long in flower, to 20.5 cm long in fruit; female flowers with stigmas expanded and spreading, plate-like. Capsules 3- or 4-valved, elliptic-ovoid, 6-15 mm long. Flowering late Apr--May, fruiting Jun--Jul. Floodplains, stream courses, shores, wet meadows, ditches and ravines, also commonly planted in yards and shelter belts; very common; (Que. to Sask., s to FL, TX and AZ).
Our representatives belong to subsp. monilifera (Ait.) Eckenw., which ranges from the Great Lakes to the Great Plains and s to n TX.
Among the species of Populus, cottonwood is the best known and the one most overwhelmingly associated with wetlands; however, balsam poplar (P. balsamifera L.) and its occasional hybrid with cottonwood, called balm-of-gilead (P. X jackii Sarg.) are sometimes found in lowland areas, especially in the eastern and northern parts of our region. Also in northern North Dakota, aspen (P. tremuloides L.) is often associated with wetland basins, although elsewhere it is typically upland in occurrence. A hybrid between P. deltoides and P. angustifolia James, called lanceleaf cottonwood (P. X acuminata Rydb.) is of uncommon occurrence along stream courses in the western portion. These entities are easily distinguished from cottonwood on the basis of tree size, leaf shape and leaf color, among other traits, but to discern between them, one should consult Eckenwalder's Populus treatment in the Flora of the Great Plains.
Reference:
Eckenwalder, J. E. 1977. North American cottonwoods (Populus, Salicaceae)
of sections Abaso and Aigeros. J. Arnold Arbor. 58:193-207.
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