Dormancy

    Canada Thistle

    Cirsium arvense

    Canada thistle

    Canada thistle flowers (Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)

    Canada thistle

    Canada thistle seedling (Phil Westra, Colorado State University, Bugwood.org)

    Canada thistle

    Canada thistle (Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)

    Description

    • broadleaf weed with spiny oblong leaves and tufted purple flowers
    • stems can be up to 1 – 4 feet tall, however it will continue to grow if mowed or cut

    Location

    • landscape, lawn and open spaces

    Life Cycle

    • perennial with extensive underground roots
    • flowering occurs June through August

    IPM Recommendations

    • Hand-pull plants in planting beds prior to seed maturation; use caution when digging out plants since underground roots that are missed can quickly regrow.
    • Apply a mulch layer 3 inches deep on planting beds to reduce seed germination.
    • If Canada thistle becomes established, post-emergent herbicides are effective, particularly with several repeat applications.