Sonchus arvensis ssp. arvensis
Weed class: C
Year Listed: 1988
Native to: Europe, Asia and Northern Africa
Is this Weed Toxic?:
not known to be
Why Is It a Noxious Weed?
Perennial sowthistle is classified as a noxious weed in many states and provinces. It is a problem in several crops where it causes economic losses due to reduced crop yields, increased cultivation and herbicide expenses and land depreciation. Perennial sowthistle was changed from a Class B to a Class C noxious weed in 2013.
How would I identify it?
A deep-rooted perennial herb, perennial sowthistle has upright, hollow stems with bitter, milky juice.
Flowerheads are bright yellow and 1.5 inches wide. Flowers open 2 to 3 hours after sunrise and close around noon. Bracts at the base of flowerheads are green, bristly and have sticky hairs.
Leaves are alternate with prickly edges and pointed lobes and varying in size. Leaves become smaller and less lobed moving up the stem.
Hollow stems are 1.5 feet to 6 feet tall, branch only at the top of the plant and have a milky juice.
Fruit Seed Description
Seeds are small, around 0.1 inches long with ridges on each side.
May Be Confused With
May be confused with prickly sow thistle (Sonchus asper), common sow thistle (Sonchus oleraceus), and though shorter, common dandelion (Taraxacum officinale). If you need help with plant identification, please contact your county noxious weed coordinator
Where does it grow?
Perennial sowthistle is found in a variety of places such as cultivated fields (both grain and row crops), waste areas, meadows, sloughs, woods, lawns, roadsides, beaches, ditches as well as river and lake shores. Please click here to see a county level distribution map of perennial sowthistle in Washington.
How Does it Reproduce?
Perennial sowthistle reproduces by seeds and creeping roots.
How Do I Control It?
General Control Strategy
Depending on the timing and type, tillage can reduce perennial sowthistle stands. Some existing evidence suggests that mowing is not as effective as tillage.
Since perennial sowthistle is palatable to both sheep and cattle, pasturing infested land can be an effective control method. There are several insects that control perennial sowthistle; however, none are available in Washington.
For More Information
See our Written Findings for more information about perennial sowthistle (Sonchus arvensis ssp.arvensis).
Thurston County NWCB Fact Sheet on perennial sowthistle
Lincoln County NWCB Brochure on perennial sowthistle