Polar hawkweed (Hieracium
atratum Fries) FamilyFamily: Asteraceae (Compositae) Description and VariationDescription and Variation: Hieracium atratum is a perennial herb, without stolons. This species usually has one basal leaf still present at flowering. The leaves found along the stem are reduced to bracts. The leaves are dentate (a few coarse teeth along the margin, with the teeth facing outward). The leaves appear mostly smooth. Polar hawkweed can range in size from six inches to 36 inches tall, depending on the habitat. The flowers are a yellow composite (dandelion-like), and they appear in mid to late summer. H. atratum H. atratum has black tipped glandular hairs, simple nonglandular hairs, and stellate hairs present on the involucre (whorl of bracts beneath the flower) and occasionally found along the upper portion of the flowering stem and leaves. A distinguishing characteristic can be the number of black tipped glandular hairs found. However, polar hawkweed is a member of a genus that belongs to a large complex without any clear specific boundaries. Economic ImportanceEconomic Importance: Detrimental: Polar hawkweed is a hawkweed species that is a prolific seed producer, with the potential to hybridize with native and non-native hawkweed species. Beneficial: There are no known beneficial uses for polar hawkweed. HabitatHabitat: Polar hawkweed grows along roadsides. Geographic DistributionGeographic Distribution: H. atratum is of European origin. This species belongs to "widespread and taxonomically difficult groups that contain many polyploids and apomictic races (which no doubt accounts for their weediness)". (Allen 1997). History: H. atratum is related to H. murorum, an introduced species which is reported from British Columbia. (Allen 1997). This species has been collected from Mt. Rainier National Park, above Longmire on the road to Paradise (Fries personal observation), at 4600’ elevation. There is another site in Skagit County, on HWY 9, near the junction with Martin Road (3/96).: H. atratum is related to H. murorum, an introduced species which is reported from British Columbia. (Allen 1997). This species has been collected from Mt. Rainier National Park, above Longmire on the road to Paradise (Fries personal observation), at 4600’ elevation. There is another site in Skagit County, on HWY 9, near the junction with Martin Road (3/96). Growth and DevelopmentGrowth and Development: Polar hawkweed is an perennial plant. ReproductionReproduction: Polar hawkweed reproduces by seeds. Response to HerbicidesResponse to Herbicides: Unknown Response to Cultural MethodsResponse to Cultural Methods: Unknown Response to Mechanical MethodsResponse to Mechanical Methods: Unknown Biocontrol PotentialsBiocontrol Potentials: Unknown Rationale for ListingRationale for Listing: Hieracium atratum is one species in a complex of hawkweeds that are prolific seed producers, weedy and capable of hybridizing with many exotic and probably native species. The fact that polar hawkweed is found at an elevation of 4600 feet and along I-5 in Skagit County may speak of its adaptability. At this time we only know of this species at one site outside of Mt. Rainier National Park. The limited distribution of polar hawkweed, makes it feasible to control the spread of yet another invasive hawkweed. ReferencesReferences: Allen, G.A. 1997. Personal correspondence. Allen, G.A. and Costanzo, B. 1997. Identification of introduced Hieracium (hawkweed) specimens for Washington State Noxious Weed Control Board. Partial Key to Hieracium of Washington State.
This page was last updated 03/31/07 |
