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DescriptionThis native or adventive perennial plant is usually 1-2' tall, but sometimes considerably higher; it often branches frequently in the upper half. The stems are covered with white hairs, and have fine lines that run vertically along their lengths. The leaves are more or less sessile and up to 5" long and 2" across. They are lanceolate, but have widely spaced pinnate lobes that are bluntly pointed. Their surface is covered with a fine white pubescence, especially on the lower side, providing them with a whitish green appearance. Upper stems terminate individually in a spike-like inflorescence about 1-4" long, which is covered with fine short hairs. This inflorescence is covered all around with small green flowers about 1/8" long on short drooping pedicels. The tiny reproductive parts of these flowers can be white or yellow; eventually, the flowers turn brown and form achenes. The pollen of the male flowers is very small and easily dispersed by the wind. The blooming period occurs from mid-summer to fall, and lasts 1-2 months. There is no floral scent. The achenes are without tufts of hair. The root system is fibrous, and produces rhizomes. This plant is a strong colonizer, in part because the root system exudes chemicals that inhibit the germination and development of other plants (allelopathy).