Canada Thistle
Cirsium arvense
Plants widely distributed in Utah. The current populations of these plants should be contained to halt their spread. These plants should not enter commercial channels.
Background
A native to southeastern Eurasia, Canada thistle reproduces by seeds and rootstock. It is adaptable to a diverse range of habitats.
Description
Canada thistle is a creeping herbaceous perennial plant usually from 1 to 4 feet tall, in sparse to extremely dense colonies. Leaves have spiny tipped lobes. Flowerheads are light pink to purple and are typically 3/4 inch in diameter. Bracts are softly spined. Bloom occurs in July and August.
Control
Several biocontrol agents are available offering fair control. Herbicides can offer good control when applied to actively growing plants from spring to fall. As with most creeping perennials, digging or tillage is generally not effective.
