Catchweed bedstraw, Galium aparine L., native to North America and Eurasia, is an annual broadleaf plant with a shallow, branching taproot. The stems of catchweed bedstraw are square in cross-section, weak, mostly unbranched, and grow to about 6 feet long, but are unable to stand on their own, so they often clamber over upright plant species.
Left on its own, catchweed bedstraw remains low and sprawling, forming dense, tangled mats. Hairlike bristles cover the stems and leaves of the plant; these bristly hairs are responsible for its characteristic tangled growth habit and the “sticky” way it clings to clothing and animals.
The leaves of catchweed bedstraw are linear, narrow, and mostly whorled, with 6–8 leaves per whorl. Inconspicuously small, pale green to white flowers occur on long stalks in the axils of upper leaves. Two-lobed, spherical fruits separate into 2 nutlets, ranging in shape from nearly round to kidney-shaped at maturity and covered with sticky hooked hairs that aid in dispersal.