Controlling Common Mullein in Pasture

Controlling Common Mullein in Pasture

May 18, 2007

Common mullein (Verbascim thapsus) is a weed species on the increase in northeastern Nebraska's rangeland, woodland and pastures. It is a biennial plant that reproduces only by seeds, but it is a prolific seed producer. Taproot of this species can access soil moisture from a deeper profile at a much better rate than fibrous roots of pasture grasses, giving common mullein the competitive advantage over grass, especially during dry years.

Common mullein usually starts growing sparsely as individual plants and then spreads further if not controlled. A cluster of leaves, commonly known as a rosette, with a thick hair cover is a distinct identifying feature of this species. The stem is woolly, erect, 2-6 feet tall, with no branches. Leaves are opposite, elliptic to ovate. Like many other plant species, the overall growth and development depends on the amount and timing of rainfall. In Nebraska common mullein can flower in June and July with yellowish flowers. It has no value to livestock because of its low palatability.

Control

Ranchers need to control this species because heavy stands can reduce grass production as much as 50%, especially in dry years, and common mullein plants have no value for livestock forage.

This weed can be controlled by various means and is best controlled at low densities. Density of this species can easily expand from a few to hundreds of plants per acre over just a couple of years due to prolific seed production. Sparse populations can be removed using a spade or shovel in late April and early May. Individual plants can be dug out or cut at the soil surface as long as the whole rosette is removed. Single mowing of new plants 1-2 feet tall can reduce population and seed production for the season, especially in dry years.

Herbicides also can be effective tools in providing season long control; however, note that the thick wooly coat of hair on the leaves can reduce herbicide uptake and control. Herbicide should be applied when the rosette has 6-12 leaves and before the stem starts to grow, which is usually in May.

Effective herbicides and their rates include: Grazon P+D (3-4 pt/ac), Cimarron (0.75-1 oz/ac), and a three-way-mix of Cimarron (0.5 oz ), Glean (0.5 oz) and RangeStar (32 oz). Make sure to use enough additives such as crop oil at 1-2 qt/ac to help herbicide penetrate the thick wooly coat.

Stevan Knezevic
Extension Weeds Specialist
Haskell Ag Lab, Concord