Photo credit: Douglas Barbe California
Department of Food & Agriculture
Botany Laboratory

Canada thistle is a unisexual, perennial from the Sunflower family, Asteraceae.

• Grows one to three feet tall.
• Has a vigorous, horizontal rootstock that produces numerous new plants creating thick patches.
• Inflorescence (flowering part of the plant) is on a branched stem consisting of light pink, lavender or rose-purple disk flowers.
• Leaves are coarse toothed, oblong with spiny irregular tipped lobes, lacking petioles.
• Originated from Eurasia and it generally has little forage value.

Young sheep and goats will eat it as well as horses will sometimes eat the flower heads. Small mammals and songbirds will eat the seeds.

Canada thistle tends to be named a “pest” plant in towns, ball fields, gardens, pastures and waste places. Plowing it will only break the root system and increases growth of new plants.

Learn more about this noxious weed from North Carolina State University, Joseph Neal.

For a complete Refuge species list

For in-depth plant information
connect with the U.S. Dept Agriculture Plant Data Base

Last Updated: 2/9/09

Plants that do not grow naturally on this short grass prairie are called "invasive species."

INFORMATION from US Fish & Wildlife

INFORMATION from USGS

ANNUAL RYE
CANADA THISTLE
CHEAT GRASS
FIELD BINDWEED
KOCHIA
COMMON MULLEIN
MUSK THISTLE
RUSSIAN KNAPWEED
RUSSIAN OLIVE
RUSSIAN THISTLE