The Importance of Identifying Weeds

  • Jan 18, 2019

Before growers implement a weed management program, it’s important to identify the weeds in order to optimize the strategies and timing of weed control measures. Dr. Lynn M. Sosnoskie, UCCE Agronomy and Weed Science Advisor, has published a blog post that can help growers identify some of the most common weeds.

Following are highlights from Dr. Sosnoskie’s article in which she focuses on members of the Asteraceae (sunflower) plant family that are found throughout agricultural regions of California. Growers can click on the name of the weed listed below to access more detailed information about the plant and view photos that will help growers identify the weed.

Hairy fleabane

This non-native plant is an annual (and sometimes a biennial) with seedlings that emerge from fall through early spring. When the plant bolts, it produces a many-branched stem between .5 – 3 feet high with cream/yellow urn-shaped flowers. Flowering takes place primarily in mid-summer through fall. Populations of this plant that are resistant to glyphosate and both glyphosate and paraquat have been confirmed in California. Hairy fleabane produces about 20,000 seeds per plant.

Horseweed

This native plant is a summer annual or biennial. It competes strongly for water, grows rapidly and is typically found in areas where natural vegetation has been disturbed. The plant produces seedlings from fall through early spring. Upon bolting, it sends up a single stem that can reach as high as 10 feet and produces cream/yellow urn-shaped flowers. Horseweed produces about 200,000 seeds per plant. Populations of this plant that are resistant to glyphosate and both glyphosate and paraquat have been confirmed in California.

Annual sowthistle

This non-native annual is a winter or summer annual plant commonly found in the Central Valley and coastal areas up to about 4,900 feet. Flowers, which resemble dandelions, can be produced year-round.

Prickly lettuce

This species is a winter and summer annual, sometimes a biennial. Plants send up a single flower stalk that can reach up to 6.5 feet. Flowering typically occurs between April – October.

Common groundsel

This species is usually a winter annual and sometimes a summer annual that produces small, yellow clusters of flowers. The plant is found everywhere except deserts, up to an elevation of 4,900 feet. Plants tend to die during extended hot and dry periods and flourish in cool, moist conditions. When ingested, the plant can be toxic to humans and livestock.

Share This Post: