Managing Summer Weeds in Pastures

Melissa Fery
Publish Date: 
Summer 2007
VolNo: 
Vol. II No. 2

A Willamette Valley Pasture Photo provided by Melissa Fery

Pesky weeds often go undetected in pastures, until summertime when they’re in full bloom. The blaze of color, purple Canada thistle, white Queen Anne’s lace or the yellow blooms of tarweed can make a landowner jump into action. Unfortunately, when weeds are blooming, most control methods are not very effective. Often, the best that can be done at this time is to mow the flowers off before seed is set to reduce the spread and then prepare a management strategy.

The first step in developing a plan for weed management is to properly identify the problem plants. Once identified, the second step is to take the time to learn about the plant’s life cycle and biology. For example, find out if the weed is an annual, biennial or perennial plant. Also be sure to study up on how the plant reproduces. Does the weed reproduce via seeds, vegetatively by a portion of the plant like a root, stem or leaf, or both? Canada thistle for example, is able to reproduce from a tiny root fragment and by seeds. Hand pulling or hoeing this troublesome weed may only create a larger thistle patch.

Armed with some basic information about your specific weeds, a year-round management plan can help determine what combination of weed control practices is best. Your specific plan may include mechanical, biological, cultural and/or chemical controls. No matter what the control measure, success in reducing weed populations requires attacking the plant when it is most susceptible. You’ll want to be ready and plan ahead for proper timing. Walking the pastures and being able to identify weeds in an early growth stage will give you the upper hand.

Your local OSU Extension Service is available to help you identify weeds. Investing in a good resource book with color pictures will also help with weed identification. The Pacific Northwest Weed Management Handbook is a great resource to help determine which control measures are effective on specific weeds. Additional weed publications are available at the Extension Service Publications and Multimedia Catalog.

Canada thistle in pasture. Learning to identify problem weeds in early growth stages will help in choosing effective control methods. Photo provided by Melissa Fery