Hawkweed common
(Hieracium, lachenalii)

Description:
Hieracium lachenalii also known as Common Hawkweed or Yellow Hawkweed is a woodland perennial which makes its home in fields and on roadsides. This common weed can grow and produce flowers on plants that range from 4 inches (10 centimeters) to 36 inches (1 meter) tall. The rhizome is short and stout.

The broadly elliptic leaves can be up to 5 inches (12 centimeters) long and taper with teeth towards the base. The flower heads have only petal-bearing ligulate (ray) florets and lack non-petal bearing tubular or disc florets (eg. as seen in the center of the sunflower head), each petal is a complete flower in itself, not lacking stamens.

Bracts surround the flower head; the receptacle (basal part of the flower on which the florets are attached) is flat and naked; heads tend to start together then become somewhat solitary on long leafless stems. The stalks below the heads are covered with scattered, simple and gland-tipped black hairs and contain a milky substance.

• Mechanical: 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.
• Biological: Not Known.
• Herbicide: 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.

For More Information:
Detailed information about Hawkweed is available at the Washington State Noxious Weed Control Board Web Site.