Hawkweeds

Hieracium sp.

Description

Note: There are five Hawkweed species of concern in the Pacific Northwest; these Quick Facts give a general overview of Hawkweeds. If you want more information about the specific Hawkweed species, check out the Additional Link to the Oregon Department of Agriculture's noxious weed list. Description: Hawkweeds are dandelion-like weeds with yellow or orange flower heads and are bristly or hairy all over. Stems exude a milky juice when broken. Flowers are borne either singularly at the top of the stem or in clusters. Young plants form rosettes of lance-shaped leaves at the base of the stem. Most species have stolons, which allow for aggressive vegetative reproduction. Native species do not have stolons; however some non-native species also lack them. Most often, the hair (its type and abundance) is used to distinguish between species.

Habitat

Open fields, mountain meadows, clearings in forest zones, roadsides, permanent pastures, cleared timber units, abandoned farmland, or other modified habitats where the soil is well-drained, course-textured, and moderately low in organic matter

Distribution

Throughout the majority of Washington, Oregon, and Idaho

Impacts

Prevent native species from establishing or surviving by out-competing them for water and nutrients and by releasing alleopathic compounds (toxic chemicals) from their decaying leaves

Dispersal Methods

Wind and human activity

Prevention

As it is difficult to spot when not in flower, survey pastures, unmanaged grasslands, and roadsides for pre-flowering and flowering from mid May to late June. Dig up isolated small populations and monitor for several years for regrowth. Prevent seeds from spreading by cleaning off equipment, shoes, and animals that have been in infested areas.

Listings

ODA's A List and OISC 100 Most Dangerous Invaders

CWMA Warnings

Upper Willamette

Columbia Gorge

Mid-Willamette

WEEDIN

Multnomah Weed Watchers