Origin:
Native to western North America, and occurring from Texas north into Canada and all states west of this.
Biology:
A summer annual weed that grows quickly to over 5 feet in height, with a multi-branching, bushy appearance. It prefers sandy soils such as river bottoms or in vacant lots, and may infest cultivated crops on such soils. It also is found along roadsides, ditch banks, and other vacant ground.
Identification:
Mature plants are bushy and up to 5 feet tall, with an open appearance due to the sparse, small leaves. Leaves are deeply lobed, sometimes forming several leaflets on a short stem, and the margins of leaves and leaflets are deeply wavy to lobed. There are short hairs on the stems and upper leaf surfaces, and longer hairs on the lower surface of the leaves. When the foliage is crushed it has a strong, unpleasant smell. Flowers are borne on long spikes that grow from the tips or upper parts of the stems, and these spikes may be 10 inches long. The flowers along these spikes are small, drooping, and mainly are the male flowers. The seed pod is a spiny bur about ΒΌ inch across, but covered with up to 30 sharp spines that are also around 1/5 long.
Characteristicts Important to Control:
Summer annuals with a strong preference for sandy soils,
