Russian knapweed
Rhaponticum repens (formerly Arcoptilon repens)
Colorado List B - Eradication required in Jefferson County
Information Sheet (pdf)
General
- Family: Asteraceae (Sunflower)
- Herbaceous perennial
- May be poisonous to horses
Habitat
- Found in pastures, rangelands, roadsides, gravel pits and grasslands
- Prefers open, sunny locations
- Tolerant to low temperatures and coarse soils
Plant
Vegetation
- Leaves 1 1/2 - 4 inches long and 1/4-1/2 inches wide
- Mature plants up to 3 1/2 feet tall
- Stems erect and branched
Roots
Flower
- Color: pink to lavender
- Season: June - August
- Size: 3/4 to 1 inches long and about 1/4-1/2 inches wide
- Bracts are tan, papery
Seed
Seedling
- Most emerge in late spring
- Some fall germination possible under optimum conditions
Reproduction
- Seed and vegetative means
Control
Biological
- None - Not a control option for Eradication species
Chemical
Cultural
- Fertilization to promote grass cover
- Prevention - maintain health of site
- Re-vegetation of highly disturbed sites
Mechanical
- Burning - Not recommended; deep roots protect the plant; areas disturbed by fire are susceptible to re-invasion due to lack of competition from desirable plants
- Grazing - Does not control; intensive grazing contributes to ideal habitat conditions, helping spread; may be toxic to livestock
- Mowing- Not recommended
Use all chemicals according to the manufacturer's label. No specific recommendation or endorsement is made or implied by listing methods or products.