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Meadow knapweed flower. -
Meadow knapweed. Photo Credit: Jennifer Andreas, Washington State University, Bugwood.org -
Meadow knapweed rosette. -
Meadow knapweed infestation. Photo Credit: (c) Keir Morse, courtesy of OregonFlora
Also known as: Hybrid knapweed
Meadow knapweed is a hybrid between black knapweed (Centaurea nigra) and brown knapweed (Centaurea jacea). Most of the meadow knapweed in Oregon grows west of the Cascade Mountains.
For a more detailed description, download the Meadow Knapweed Best Management Practices factsheet.
Description:
| Life Cycle: | Perennial (life cycle lasts more than one year) |
| Early Detection and Rapid Response species: | No |
| Height: | Up to 3.5 feet (1 meter) tall |
| Leaf Description: | Rosette leaves are deeply lobed. Mature leaves are pale green and hairy. They become smaller further up the stem. |
| Fruit & Flower Description: | Pink to purple flowers have light brown to black bractsBracts Leaf-like structures below a plant’s flower.. Flowers are solitary, meaning a single flower grows at the end of a single stem. Its features can vary because of hybridization. |
| Bloom Time: | June to September |
How it spreads:
- Meadow knapweed spreads through seeds, which can be moved in contaminated hay or other agricultural goods.
- Cars, equipment, clothing, animal’s fur, and moving water can also spread seeds.
Habitat:
- Knapweeds are pioneer species that thrive in open, sunny habitats.
- Meadow knapweed can grow in places with moist soil such as wet meadows and along riverbanks.
Impact:
- Meadow knapweed outcompetes and suppresses native vegetation, decreasing plant diversity and wildlife habitat.
- It increases the cost of agricultural production by competing with crops and reducing forage for livestock.
What you can do about it:
- Manual: Small patches can be dug up with a shovel or hand pulled. Knapweeds are easiest to remove in the spring when the soil is moist, and the plants are still rosettes. Make sure to remove as much of the root as possible to prevent resprouting.
- Dispose of all plant materials in a tied plastic bag and throw it away in the trash – not the yard debris.
- Cultural: Once removed, make sure to reseed bare patches of pastures with competitive, perennial grasses to prevent knapweeds from regrowing.
Look-alikes:
There are many invasive knapweeds across the Pacific Northwest including diffuse knapweed (Centaurea diffuse) and spotted knapweed (Centaurea stoebe). The key to identifying different knapweed species is to closely examine each species’ flowers. Meadow knapweed’s flowers are pink to purple, and its bracts lack dark upside-down V markings.
Noxious Weed Listing:
| State of Oregon: | Class B |
| State of Washington: | Class B |
More Resources:
- Pacific Northwest Weed Management Handbook: Knapweeds
- University of California, Weed Research & Information Center: Meadow knapweed