Stem

Up to 4 ft. tall, green to brown, branched at the top and usually lacks hair (glabrous)

Leaves

Alternate, oblong or lance-shaped, 2-8 in. long, shiny and lack hair; NO leaf stems (petioles); leaf edges (margins) are wavy, lobed or toothed with spiny edges

Canada thistle rosette

Flower

Pink, purple or white; occur in clusters at the ends of branches; base of flower is vase-shaped, 0.5-0.75 in. wide, lacks prickles and is covered with green to purple bracts with dark tips

Canada thistle flowers

Root

Deep, extensive creeping root system

Other

Grows best in moist areas; often found in pastures, hay fields, waste areas and along waterways; known to occur throughout Nevada
Perennial; reproduces by both roots and seed; plants often appear in patches or colonies due to the spreading root system

Control

Repeated mowing, tillage, cutting or hand removal prior to seed production can provide suppression
Several biological control agents are available
Apply aminocycloprachlor, aminopyralid, chlorsulfuron, clopyralid or picloram pre- or post emergence; repeated applications of 2,4-D, dicamba or glyphosate to actively growing plants

Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Nevada Noxious Weed Field Guide – Canada thistle, Extension, University of Nevada, Reno, Field Guide

Extension Associated Contacts

Heidi Kratsch

Also of Interest:


Insect Management Applying IPM strategies: Insect control can be split into these five separate categories. Hefner, M. 2019, Extension, University of Nevada, Reno
Pesticide Labels Explained Tips for considering when to use a pesticide and the basics of reading pesticide labels. Jensen, C. and Kratsch, H. 2023, Extension, University of Nevada, Reno
A Northern Nevada Homeowner's Guide to Identifying and Managing Earwigs This fact sheet describes the identifying features, life cycle, plant damage, and control methods for managing earwigs in Nevada. K. Burls, W.Hanson Mazet, H. Kratsch 2021, Extension, University of Nevada, Reno, FS-21-108
A Northern Nevada Homeowner's Guide to Identifying and Managing Shield Bugs This fact sheet describes the identifying features, life cycle, plant damage, and control methods for managing Shield Bugs in Nevada. K. Burls, W. Hanson Mazet, H. Kratsch 2021, Extension, University of Nevada, Reno, FS-21-110
A Northern Nevada Homeowner's Guide to Identifying and Managing Squash Bugs This fact sheet describes the identifying features, life cycle, plant damage, and control methods for managing Squash Bugs in Nevada. K. Burls, W. Hanson Mazet, H.i Kratsch 2021, Extension, University of Nevada, Reno, FS-21-111

Associated Programs

Master Gardeners of Douglas County

Learn about the Master Gardener program in Douglas County, Nevada.

Master Gardeners of Nevada

Program trains local gardeners to provide research-based horticulture information to Nevadans

Master Gardeners of Washoe County

Master Gardeners provide free, research-based horticulture information to Nevadans.

Nevada Noxious Weed Field Guide – Canada thistle