European Hawkweed
Hieracium sabaudum

European hawkweed, also called savoy hawkweed, is a tall perennial with many small dandelion-like flowers and multiple, stout leafy stems from a single root crown.  Like other hawkweed species, this plant is highly invasive and will spread over large areas if not controlled.

European hawkweed is a Class A Noxious Weed in Washington State due to its limited distribution in the state and the potential for significant impact to state resources. Public and private landowners are required to control this plant when it occurs on their land. Because of the difficulty to distinguish this plant from more widespread weeds, we recommend contacting the noxious weed program for a positive identification before removing.

Identification (see below for more photos)

• Multiple upright, leafy stems up to 4 feet tall from a single root base
• Numerous, small, dandelion-like flowers in a loose, branched, flat-topped candelabra shaped cluster
• Bloom time is late July to October
• About 50 stem leaves, larger and denser near the bottom and getting smaller up the stem
• Leaf edges strongly toothed, leaves tapered and narrow toward the base
• Lower surface of leaf has long, slender hairs
• Stems have a milky juice
• Lower portion of stem covered with dense, long, white hairs (see photo below)
• Stalks below flowers have soft white hairs 
• Does not form stolons

Habitat and Impact

European hawkweed is found mostly on roadsides and in open fields, forest clearings and other disturbed areas. Typically found where soil is well-drained, coarse-textured, and low-nutrient. Can form large infestations along roadways and in open fields. Currently Euroepan hawkweed is very limited in distribution in Washington State.

Growth and Reproduction

European hawkweed reproduces by seed. Because seed production is mostly asexual, hawkweeds do not depend on pollination and can rapidly dominate an area due to its high seed production. Hawkweeds are perennials and can thrive in a wide range of conditions. Seeds can disperse long distances.

Control

Small populations can be removed by digging. Make sure to remove the entire root since plants can resprout from root crowns. If plants are in flower, bag and discard flowering stems to avoid spreading seeds.

Do not control by mowing unless mowers can be cleaned before moving to new areas and all the flowering stems can be collected and discarded. Plants will re-grow after being mowed and flower again in the same season.

Large areas infested with hawkweed are highly difficult to manage. In areas where hawkweed is still limited in distribution, every effort should be made to contain and reduce the hawkweed before it is too established to control.

Selective herbicides have been most successful in managing hawkweed because they allow the grass to remain in place, greatly reducing the germination of hawkweed seeds in the soil and slowing down re-invasion by the hawkweed.

Hawkweed management needs to be combined with altering the conditions in the plant community to favor grasses and native plants. If holes left after controlling hawkweed are not filled quickly with desirable species, hawkweed is likely to re-infest the area. Since hawkweed often grows in low-nutrient, low-organic soils, amending the area with fertilizer and organic matter can help reduce re-infestation by hawkweed when combined with active management of the hawkweed.

Make sure to have a long-term plan to ensure success, protect native and beneficial species while doing the control, and start in the least infested areas first and then move into the more heavily infested areas.

European Hawkweed Photos - click thumbnail for larger image