Noxious Weeds Profile - Sowthistle, annual, perennial

Table of Contents


  • English - annual sowthistle, perennial sowthistle
  • French - laiteron lisse, laiteron des champs
  • Latin Name - Sonchus oleraceus L., Sonchus arvensis L.


Annual sowthistle.

Figure 1. Annual sowthistle

Perennial sowthistle.

Figure 2. Perennial sowthistle

Current Status

  • Ontario Weeds Act - noxious
  • Other provinces - noxious in AB, BC, MN, QC, SK (perennial); AB, BC, MN, QC, SK (annual)
  • Canadian Federal Seeds Act - perennial Class 2 & 5
  • U.S. Federal Noxious Weed - no
  • U.S. Noxious State Reg - perennial 18 states (including Illinois, Indiana, Mich, Ohio, Penn); annual none


  • Pub 505 - no
  • NE Weeds - no
  • Canadian Poison Plant - not listed
  • Cornell Poison Plant - not listed


  • Throughout Ontario in cultivated fields, pastures, meadows.

Growth Habit

  • Annual and Perennial

Method of Propagation

  • Seeds (Wind blown)


  • Annual - Susceptible to 2,4-D and dicamba and listed on 2,4-D and Roundup labels. A single mowing before flowering can give effective control.
  • Perennial - Susceptible to dicamba and glyphosate and top growth control only with 2,4-D. Listed on 2,4-D, Banvel and Roundup labels. Apply herbicide at early bud (flowers mid summer) or in early fall. Repeated mowing at 21 day intervals can be an effective control.

Related Links


For more information:
Toll Free: 1-877-424-1300
Author: Mike Cowbrough - Chief Weed Inspector Ontario Weeds Act/OMAFRA
Creation Date: March 2003
Last Reviewed: 29 December 2006