Yellow Hawkweed (Hieracium
caespitosum Dumort.) Family: Compositae Description and VariationDescription and Variation: Yellow hawkweed has bristly-haired, narrow, elongated leaves four to six inches long. The leaves are attached near ground level and the flowering stalk, arising from the leaf cluster, is leafless. The flowering stalks grow from a few inches to three feet in height; the stems have short, stiff hairs and contain a milky latex sap inside the stem. The flowers, which are about the same shade of yellow as buttercups, occur in heads that are about 3/4 of an inch in diameter. Economic ImportanceEconomic Importance: Yellow hawkweed is destructive in rich pasturelands and may even invade cultivated fields. Yellow hawkweed is unpalatable and thus crowds out more palatable species. Geographical DistributionGeographical Distribution: In the state of Washington, H. caespitosum is mainly located in northeastern Washington. However, it has also been found in portions of western Washington. HabitatHabitat: Yellow hawkweed occurs in permanent meadows, rangelands, and pastures. HistoryHistory: Yellow hawkweed was first introduced from Europe into northern New York about 1879. It is a fairly recent importation from Europe, but it has spread rapidly. Growth and DevelopmentGrowth and Development: Yellow hawkweed is a perennial plant. ReproductionReproduction: This species can spread by seeds, stolons, and/or rhizomes. Response to HerbicidesResponse to Herbicides: Early season treatment with picloram, combinations of picloram plus 2,4-D, or dicamba mixed with 2,4-D can be effective in controlling the hawkweed, but 2,4-D alone is inadequate. See current herbicide labels and recommendations for herbicide doses to be used. Response to Cultural MethodsResponse to Cultural Methods: In scattered patches of small size, the simplest mode of attack is to dig them out, making sure that all of the below-ground growth is also removed, since even a small piece may develop into a new plant. These plants should be either burned or placed in a refuse pile where they can do no harm. Biocontrol PotentialsBiocontrol Potentials: Dr. Joe McCaffrey of the University of Idaho is currently investigating possible biocontrol agents. ReferencesReferences: Callihan, R.H., C.C. Thill and D.W. Wattenbarger. Hawkweeds. Current Inf. Series No. 633. University of Idaho Cooperative Extension. Hansen, Albert A. 1920. The Hawkweeds, or Paintbrushes. Circular 130. U.S.D.A. Old, Rich. 1984. Plant Notes. NotesNotes: While Hitchcock and Cronquist states that Hieracium pratense (H. caespitosum) is "locally introduced in NE Washington" this information is rather deceptive. I [Rich Old] have just completed an extensive survey of both Hieracium species in northern [Idaho] counties and reported it as for south as Camas County. The two Hieracium species [H. caespitosum and H. aurantiacum] often occur together in urban sites, with H. caespitosum being much more ubiquitous in the forest communities and lowland pastures of Benewah and Kootanai counties, as well as throughout the St. Joe National Forest. The ubiquitousness of H. caespitosum at first had me puzzled until I encountered a note from the original collection in the northwest by Earle F. Layser 6/9/69 "Introduced by U.S. Forest Service grass seedings." Most of these seedings, especially in clearcut areas, are flown on.
This page was last updated 03/31/07 |
