Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
21. Salicaceae, the Willow Family
1. Populus L. -- Aspen, cottonwood, poplar
1. 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.
Eckenwalder, J. E. 1977. North American cottonwoods (Populus, Salicaceae)
of sections Abaso and Aigeros. J. Arnold Arbor. 58:193-207.
Return to Family -- Salicaceae - The
Next Species -- Salix alba L. -- White willow