Worldwide there are over 700 species of “hawkweeds”, mostly in Europe and South America. The ancient Greeks believed that hawks would tear apart the plant and wet their eyes with the juice to clear their eyesight. The Roman naturalist Pliny thought hawks fed on these plants to strengthen their eyesight. Both the Greeks and Romans used the work “hierakion” (from the Greek “heirax” meaning “hawk”) for hawkweeds or the plants hawks used to improve their eyesight. Thus the etymology of the genus name Hieracium.
White hawkweed (Hieracium albiflorum) is native to Western United States and Western Canada. Populations of white hawkweed are also introduced in Wisconsin and Quebec. Found below 9,700 feet, this perennial prefers mineral soils in relatively dry open forests, meadows, clearings and roadsides.
Also commonly called white-flowered hawkweed, H albiflorum has an erect stem growing from a fibrous base (caudex). The plant, which can grow to about three feet in height has a milky juice or sap.
The leaves are mostly basal, stalked and bristly with short, rigid hairs on the upper surface. The lower surface of the blade usually has hairs only on the midvein. The basal leaves are oblong to lanceolate with entire and sometimes wavy margins. When present on the stem, white hawkweed leaves are alternate, reduced in size and sessile (no stalk).
A member of the Sunflower Family, the white hawkweed inflorescence is a pannicle (branched and maturing from the bottom upward). The flower heads are composed of white ligulate flowers. Ligulate flowers have a strap-shaped, five-toothed corolla (petal) and a fertile pistil and stamens (bisexual).
White hawkweed fruits are achenes (dry, hard and containing one seed) with tawny pappus bristles.The seeds are wind dispersed.
White hawkweed has low resistance to fire and decreases in number after a burn. However, the wind-blown seeds quickly repopulate burned areas and white hawkweed populations regain their pre-fire frequency quickly.
In some areas white hawkweed is considered an invasive or noxious weed.
The species name derives from Latin and means “white flowered”.
These white hawkweed specimens were growing along the Pacific Crest Trail near McArthur Burney Falls State Park (Shasta County CA) in June.