Life cycle: Biennial
Stems: Several branched, upright stems
Flowers: are purple to pinkish with
Spotted knapweed seeds can remain viable for 7-10 years
Note: This weed has allelochemicals or allelopathies that inhibit other plant species from growing within their vicinity. When hand-pulling make sure to wear gloves.
Effective control methods:
Cultivation/ hand-pulling, herbicide, bio-controls
Hand pulling small infestation works very well if the majority of the taproot is removed.
Using a selective herbicide will greatly decrease knapweed and increase grasses, which will help out-compete knapweed infestation.
Cultivation works well in controlling small infestations of spotted knapweed
Mowing will reduce seed production very well for that year but will not kill the plant. The plant will adapt to the height of the mower blade and resume seed production at that height.
Bio-controls: Root weevils (Cyphocleonus
*successional degradation – replaces one unwanted species with another.