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Tyrol knapweed

(Centaurea nigrescens)

Photo of Tyrol knapweed
Photo credit: Joseph M. DiTomaso, UC-Davis, Bugwood.org

Perennial knapweed with lavender flowers and fringed bracts that are long and slender with dark brown tips.

Overview

Other names for this plant include:
  • Common names: Vochin knapweed, alpine knapweed, Wocheiner knapweed, and short-fringed knapweed
  • Scientific names: Centaures vochinensis, C. dubia
Ecological threat:
  • Invades open grasslands, prairies, open forests, orchards, cultivated fields, field edges and travel corridors.
  • Aggressively outcompetes desired vegetation, reducing overall biodiversity and forage quality.
  • Plants are easily spread by human activity via seed and the plants' characteristics facilitate seed dispersal across long distances.
  • Plants produce hundreds of seeds per plant.
  • It increases soil erosion and consumes soil nutrients.
Overview map of Tyrol knapweed classification in WI
Restricted (orange) counties

Classification in Wisconsin: Restricted

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for Tyrol knapweed was based upon this literature review [PDF] developed by the department.

Identification

Leaves & stems: A single upright stem branches near the top. Basal leaves are oblanceolate to elliptic. Upper leaves are lanceolate and progressively decrease in size up the stem. Leaves are hairless or lightly hairy on the undersides; deeply lobed to irregularly cut. The terminal lobe is much larger than the others.

Flowers: Flowers are lavender to purple in color and occur singularly at the ends of branches. Bract (long fringes beneath the flowerhead) tips are dark brown in color and long and slender. Bract tips have a somewhat triangular fringe.

Fruits & seeds: Seeds are tan in color with fine hairs. Plants produce on average a few thousand seeds per plant.

Roots: Plants have taproots.

Similar species: Tyrol knapweed closely resembles other knapweeds, the majority of which are also invasive in Wisconsin.

Control

Mechanical:
  • Handpull the plants, being sure to remove the entire taproot.
  • Mow or cut plants before flowering to prevent seed-set. Note this will not immediately kill the plants; continual cutting is needed to exhaust root reserves.
  • Monitor for regrowth.
Chemical:
  • Herbicide treatments are most effective when combined with other control techniques and followed by re-seeding. The timing of herbicide treatments is essential to effectiveness.
  • A three percent solution of triclopyr herbicide mixed with water can be applied to the leaves in early spring or fall.
  • Glyphosate, picloram, 2, 4-D and clopyralid have all been used on other knapweeds
Biocontrol:
  • Gall flies (Urophora affinis and Urophora quadrifasciata) are used to feed on the developing seed heads.

Photos

View tyrol knapweed pictures in our photo gallery!

Resources

Sources for content:
  • Alberta Agriculture and Rural Development
  • Washington State Noxious Weed Control Board
  • USDA Forest Service
Links for more information: