Sonchus arvensis ssp. arvensis (syns. Sonchus arvensis var. shumovichii)
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.
Height of mature plants
1.5 feet to 6 feet
March through June
Common sowthistle, Sonchus oleraceus, is similar but is an annual species.
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.
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.
Noxious Weed Listing:
- WeedWise: Maintenance
- State of Oregon: Not listed
- State of Washington: Class C
- Four County CWMA: Class D
Europe, Asia and Northern Africa