CITY AND COUNTY OF BROOMFIELD PARK OPERATIONS
NOXIOUS WEED IDENTIFICATION
CANADA THISTLE, Cirsium arvense (L.) Scop.
Characteristics:
Family: Asteraceae (Sunflower)
Origin: Europe
Description:
- Deep rooted perennial
- Reproduces by seed and root stock
Stems:
- Erect, hollow, smooth, slightly hairy
- 1-5 feet tall, simple and branched at the top
Flowers:
- Pink to purple colored flowers
- Bloom occurs June-August
- Multiple flowers are small and compact, 3/4" in diameter
- Seeds are 1/8th inch long and are tufted, like dandelion seeds and are easily distributed by wind
Leaves:
- Attached close to the stem
- Dark green in color
- Covered with sharp spines
Location:
Canada Thistle is a very common and problematic weed. The root system is often extensive. It propagates quickly and is spread rapidly, especially in riparian ecosystems. It is very competitive and can grow in dry areas, as well. Canada Thistle is distributed along roadways, forests, lawns, rangeland and riparian areas up to 9,500 feet.