Common cocklebur is a highly branched, taprooted, broadleaved annual that grows from 8 inches to 6 feet (0.2 to 2m) high. The dull green leaves alternate along the stem, are coarsely toothed, and often have three to five shallow lobes. The leaf stalks are about as long as the leaves.

The flower heads of common cocklebur are unisexual. Small male and female flowers form separate clusters. Male (staminate) flowers are in short terminal spikes or clusters, and the burlike female (pistillate) flowers are in axillary clusters. The distinct seed pods, or burs of cocklebur make the weed easy to identify. Burs are light brown, Y2 to 1 inch (1 to 2.5 cm) long, and oval or oblong. They are covered with stout, hooked prickles, which terminate in two hooked spines. Each prickle is 1/10 to ¼ inch (2 to 6 mm) long.

Each bur contains two brown to black achenes (seeds), one above the other. The lower seed can germinate immediately; the upper seed is dormant and does not germinate until months or often years later. Seeds are about ½ inch (12 to 14 mm) long and 1/5 (4.5 to 5 mm) wide. Mature burs are dispersed primarily by humans and animals.

Seeds germinate from early spring through summer, from depths of up to 6 inches (15 cm). Seeds and small seedlings are toxic to humans and livestock, but toxicity decreases rapidly as the first true leaves develop. Regardless of size, common cocklebur flowers from August through October in response to day length.

Complete control of common cocklebur is often difficult because some of the seeds remain dormant in the soil for months or even years. Early-season control is important because cocklebur grows rapidly and, once established, can be a long-term problem.

The most effective control measure is to prevent seed production. Cultivation practices and herbicide applications can also be effective. No single herbicide gives good full-season control; therefore, both preemergence and postemergence herbicide applications are necessary.

For most effective postemergence control, cocklebur must be shorter than 8 inches (20 cm) at time of treatment, and herbicides must be applied under good growing conditions.

For specific recommendations, contact the County Weed Office at<personal data hidden>.

Hope this helps.
Darrin Parmenter

*Some information taken from Penn State University Extension factsheet