Nonnative Hawkweed Species & Hybrids of Wall Subgenus
Hieracium subgenus Hieracium
Washington State Classification
Class B — Control Required (Designated)
These nonnative hawkweed species and hybrids are invasive, spread readily, and have negative impacts to rangeland and other habitats, especially in mid to upper elevations and in areas with low fertility soils.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
Perennial, herbaceous plants that exude a milky sap when broken, have various types of hairs, and flowerheads of yellow flowers. Nonnative hawkweed species can be difficult to tell apart, especially if they hybridize. Nonnative yellow flowered hawkweeds are grouped into two Class B noxious weed listings by subgenus Pilosella and subgenus Hieracium. Nonnative hawkweeds in the wall (Hieracium) subgenus include: European (Hieracium sabaudum), smooth (H. laevigatum), common (H. lachenalii), polar (H. atratum), spotted (H. maculatum), and wall (H. murorum).
Leaves
Plants in this subgenus typically have basal leaves and stem leaves. Leaf edges are toothed or lobed.
Flowers
Flowerheads are composed of all yellow ray flowers (dandelion-like). Bracts at base of flowerheads have various types of hairs. Flowerheads are generally in clusters.
Fruit & Seeds
Seeds are small, with ribs or grooves and have bristles on one end.
Impact
These nonnative hawkweed species and hybrids are invasive, spread readily, and have negative impacts to rangeland and other habitats, especially in mid to upper elevations and in areas with low fertility soils.
Ecology & Spread
Habitat
Typically found in fields, meadows, pastures, forest clearings and disturbed areas such as roadsides and abandoned farmland. Please click here to view a county level distribution map of nonnative hawkweed species and hybrids of the wall subgenus in Washington.
Spread Mechanisms
Reproduction
Plants in the wall subgenus primarily reproduce by seed.
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Control Methods
Mechanical
- Mechanically controlling hawkweed species can be difficult to do in pastures and rangelands. Mowing plants to get rid of flowerheads only stimulates vegetative growth. If there are only a few plants, hand digging is a feasible option, but all of the roots must be removed. Once plants are dug up, put them into a city yard waste container or throw them in the trash. Do not put pulled plants in home compost piles as they might not get hot enough to kill them, and many species can vegetatively spread.
Cultural / Prevention
- Careful digging is useful to manage weed populations. However, digging can carry undesirable weed seed to the surface and foster further germination.