Populus tremula L.
aspen
Tree to c. 16 m high, often suckering profusely, widespreading, almost glabrous. Bark greenish or yellowish green, rather smooth, except near base. Shoots dark, slightly hairy at first, slightly angular when young, otherwise terete. Buds not viscid, glabrous. Young lvs not aromatic. Lvs hairy at first, soon glabrous. Petiole 2-7 cm long, strongly flattened. Lamina 2.5-12 × 3-12 cm, broad-ovate to suborbicular, sometimes broader than long, green above and glaucescent or glaucous below; margin without translucent band, coarsely crenate-serrate or crenate-dentate, with teeth often curved; base truncate to subcordate, sometimes with 2 glands; apex acute. Catkins ♂, to 10 cm long, pendulous. Rachis densely hairy. Bracts 2.5-4 mm long excluding oblong to triangular teeth, brown, densely fringed with long silky hairs. Cup-shaped disc 1.5-2.5 mm deep, oblique, glabrous. Stamens mostly 6-10; filaments very short; anthers purple.
S.: Canterbury (forming dense stands in a few places).
Temperate Eurasia 1940
Pastures adjacent to old plantations and shrubberies.
FL late Aug-early Sep.
Aspen is planted occasionally in N.Z., particularly in the South Id and colder parts of the North Id. ♀ trees are rare and only seen in cultivation; they have pendulous catkins to c. 8 cm long, and the bracts and cup-shaped disc smaller but otherwise similar to the ♂. The trembling or quivering of the lvs is a result of the very flattened petiole which allows the lf to move with the slightest breeze. This feature is also found in other aspen poplars. One of these, P. tremuloides Michaux, American aspen, has been recently planted in a number of places in N.Z. It is a closely related N. American sp. but has pale yellowish bark when young and lvs with finely crenulate-serrulate margins which are hairy when young.
