Also called clotbur, donkey bur, heartleaf, and woolgarie bur, this weedy annual is a member of the aster family, Asteraceae, that also includes sunflower, yarrow, and lettuce. It’s native range is uncertain but it is found throughout the US today where it grows in a variety of habitats such as cultivated fields, coastal dunes, watercourses, and waste places. Cocklebur prefers moist to wet sandy loam or loams in full sun to partial shade. It has been used in traditional medicine especially in South Asia to treat many ailments including aches and pains, respiratory allergies, sinusitis, headache, gastric ulcer, urticaria, rheumatism, arthritis, and bacterial and fungal infections. The seeds and leaves of young seedlings are considered toxic to livestock and humans. Photo Credit Franco Folini Wikipedia Commons
Description: Seedlings begin to appear in the spring and continue into summer. The seedling stems are purple at the base and bear large medium green leaves. As the seedling matures, erect, branched stems grow 2-6 1/2 feet high and are covered with short stiff hairs, bumps, and longitudinal ridges. The stems are green with maroon to black spots and bear alternate leaves on long petioles. The lobed leaves are 2-6” long, triangular to ovate, and have stiff hairs. Clusters of inconspicuous green male and female flowers are produced on the same plant on short petioles arising from the leaf axils. Green burs develop from the female flowers, each containing 2 seeds, one germinating the following year, the other germinating the year after. Each bur is about ½” long and is covered with hooked barbs, with two extra long ones at one end. The burs turn brown as they mature and hook onto animals as they pass by. A single plant can produce 400 seeds in a season. The root is a taproot.
Control: Young plants are easy to pull up or hoe out but as the plant matures the taproot develops and removing the plant becomes more difficult. Mature plants can be cut down by mowing, disking or weed whacking well below the soil line so that new stems do not emerge. Removing the tops before the seeds ripen is essential since seed is the only method of reproduction and can remain viable in the soil for 16 years. Since the plant is an annual it will die at the end of the growing season.
For large populations herbicides may be needed. A pre emergent herbicide such as Acuron will reduce the number of new plants that appear. Once the plants have appeared a post emergent herbicide such as 2,4 D or Dicamba is useful if applied in the spring when the plant are actively growing.
