Native to the Mediterranean, but now found throughout the world. In the United States it occurs along the eastern seaboard states from Vermont to Florida and west to Texas. It also is found in Utah and Hawaii, and in southern Canada.
This is a warm season annual weed that reproduces from seeds. The plant may be either erect and bushy or may grow prostrate, with flower clusters produced from the summer into the fall. This is a weed of most habitats, from turf to roadsides, landscape and row crops to disturbed waste lots.
The stems are smooth and reddish, with angled ridges along them. The leaves are hairy and more or less oval, often wider just past the middle. There usually is a notch at the tip of the leaf, and the leaves are on long stalks. The flowers are in dense clusters at the ends of the stems, beginning green and turning to a more reddish color as they mature.
Hand removal is possible for individual plants. When growing in turf a selective broadleaf herbicide will effectively kill this weed, or a non-selective herbicide in other situations.