Comprehensive DescriptionRead full entry
DescriptionThis annual plant is either introduced or native and somewhat variable in appearance. Depending on the fertility of the soil, it is 1-6' tall, branching occasionally. Large mature specimens have a bushy appearance, tapering gradually toward the apex. The stems are stout, angular, and variably colored, ranging from light blue-green to striped with purple and green. Young stems are covered with a fine mealy pubescence, while older stems become more glabrous. The alternate leaves are up to 5' long and 3' across (excluding the petioles). The older lower leaves are broadly lanceolate or ovate with irregular margins. These margins are undulate, slightly lobed, and/or dentate, and they are sometimes reddish purple along the edge. The dentate teeth are large, widely spaced, and blunt. The upper surface of the lower leaves is usually green or bluish green and glabrous, while the lower surface may be glabrous to more or less white mealy with tiny white hairs. The petioles are slender and long, often at least half the length of the leaves. The upper leaves have a similar appearance to the lower leaves, except that they are smaller, more narrow, and more white mealy from the presence of tiny white hairs, which are present on both the lower and upper surfaces. The major upper stems and some of the side stems terminate in panicles of flowering spikes. On large plants, the individual spikes of this inflorescence may be up to 8' long, but they are usually less than half this size. The inconspicuous yellowish green flowers are sessile against the flowering stalks and densely distributed. Each flower is about 1/10' across, consisting of a green calyx with 5 acute lobes, no petals, 5 stamens with yellow anthers, and a short style that is cleft into 2 or 3 parts toward its apex. The calyx is conspicuously white mealy across the outer surface, and its lobes are slightly keeled. The blooming period can occur from mid-summer through the fall, and lasts about 1-2 months for a colony of plants. The flowers are wind-pollinated. The ovary of each flower matures into a single horizontal seed that is black, flattened, and nearly round. The lobes of the calyx curl inward and wrap around this seed, more or less obscuring it from view, except for a tiny opening at the top. This seed has a gray membranous covering that is difficult to remove. A single plant can produce 50,000 or more seeds. The root system consists of a taproot that is short and stout. This plant spreads by reseeding itself, sometimes forming sizable colonies.