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Yellow Devil Hawkweed (Hieracium floribundum) Family: Asteraceae (Compositae) Description and Variation: Yellow devil hawkweed is a perennial herb with many slender and leafy stolons (horizontal stems) at the base of the plant, and a long rhizome (underground stem). This hawkweed has a well developed cluster of basal leaves at time of flowering in the early summer. The basal leaves are glaucous (covered with a whitish or bluish waxy coating), and as large as or larger than any of the upper leaves. The top of the leaf is smooth whereas the underside of the leaf has scattered, bristly hairs, particularly along the mid-rib. The leaves range in size from 1½ - 5 inches long, the leaf shape is longer than wide, with the widest part being near the tip. The leaf margins toward the base are also covered with long bristles. The leaves along the stolon are more hairy than the basal leaves. The single flowering stem is 8 - 32 inches tall, sparsely scattered with long bristles that are blackish and tipped with star-like glands. The complete flowers are yellow composites, with 3-50 flower heads in a flat-topped cluster. The bracts under the flower heads have the same stiff hairs (as along the stem) that are blackish and tipped with star-like glands. (Gleason and Cronquist 1991; Muenscher 1995). Yellow devil hawkweed is thought to have originated with hybridization of H. caespitosum (yellow hawkweed) and H. lactucella. (Gleason and Cronquist 1991). The distinguishing characteristics of yellow devil hawkweed may be the glaucous leaves, a longer rhizome, and many slender and leafy stolons. Economic ImportanceEconomic Importance: Detrimental: It is closely related to H. pilosella (mouseear hawkweed), a Class B noxious weed. It can outcompete pastures, rangelands, and native plant species. Beneficial: None known. HabitatHabitat: Yellow devil hawkweed grows in meadows, roadsides, and fields. Geographic DistributionGeographic Distribution: Native to Europe, H. floribundum is one species of this genus that belongs to a large complex without any clear specific boundaries. There are hundreds of species with thousands of names, established in mostly temperate or mountainous tropical regions. This weediness is in part due to the capability to produce seed without fertilization, and to the number of complete sets of chromosomes in each cell. (Gleason and Cronquist 1991). History: Yellow devil hawkweed is found in Thurston County, Washington and in Whatcom, County, Washington. It was introduced to North America in 1900 (Reader and Watt 1980). Herbarium samples from the University of Washington include specimens from New Brunswick, Canada 1929; Vermont 1925; and New Hampshire 1977. It is considered a pest in the eastern part of British Columbia. (Allen, pers. communication) Growth and DevelopmentGrowth and Development: Yellow devil hawkweed is a perennial that spreads by seed and stolons. ReproductionReproduction: Yellow devil hawkweed has prolific seed production and is capable of producing seed without fertilization. It also spreads by stolons. Response to HerbicidesResponse to Herbicides: Unknown. Response to Cultural MethodsResponse to Cultural Methods: Adding fertilizer (NPK) to abandoned pastures halted or reversed patch formation by hawkweeds, particularly in areas that had a high proportion of grasses. Grass growth increased after pastures were fertilized. This contributed to shading out the hawkweeds and increasing a pathogen habitat against hawkweeds. H. floribundum and H. pilosella are negatively impacted by increased shading. Fertilization as a control only worked in the plots that were dominated by established grasses. (Reader and Watt 1980). Response to Mechanical MethodsResponse to Mechanical Methods: Unknown. Biocontrol PotentialsBiocontrol Potentials: Unknown. Rationale for ListingRationale for Listing: Hieracium floribundum 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. H. floribundum is closely related to mouseear hawkweed, a Class B noxious weed capable of overtaking native plants and habitat. The limited distribution of H. floribundum at this point in time makes it feasible to eradicate and halt the spread of yet another invasive hawkweed. References: 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. Bradshaw L. and D. Goldberg. 1989. Resource Levels in Undisturbed Vegetation and Mole Mounds in Oil Fields. The American Midland Naturalist. 121(1):176-183. Gleason, H. A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second Edition. The New York Botanical Garden, Bronx, NY. pp. 621-625. Muenscher, W. C. 1955. Weeds. Second Edition. Cornell University Press. Ithaca and London. pp. 474-477. Reader, R.J. 1990. Competition constrained by low nutrient supply: an example involving Hieracium floribundum Wimm & Grab. (Compositae). Functional Ecology 1990, 4, 573-577. Reader, R. J. 1978. Structural changes in Hieracium floribundum (Compositae) population associated with the process of patch formation. Canadian Journal of Botany: Vol.56, (1978), No. 1. pp 1-9. Reader, R. J. and B. J. Best. 1989. Variation in Competition Along an Environmental Gradient: Hieracium floribundum in an Abandoned Pasture. Journal of Ecology: Vol. 77, 1989. pp 673-684. Reader, R. J. and J. Buck. 1986. Topographic Variation in the Abundance of Hieracium floribundum: Relative Importance of Differential Seed Dispersal, Seedling Establishment, Plant Survival and Reproduction. Journal of Ecology: Vol. 74, 1986. pp. 815-822. Reader, R. J. and A. G. Thomas. 1977. Stochastic simulation of patch formation by Hieracium floribundum (Compositae) in abandoned pastureland. Canadian Journal of Botany: Vol. 55, 1977. pp 3075-3079. Reader, R. J. and W. H. Watt. 1980. Response of hawkweed (Hieracium floribundum) patches to NPK fertilizer in an abandoned pasture. Canadian Journal of Botany: Vol. 59, 1981. pp 1944-1949. Thomas, A.G. and H.M. Dale. 1975. The role of seed production in the dynamics of established populations of Hieracium floribundum and a comparison with that of vegetative reproduction. Can. J. Bot. Vol. 53, 1975. pp. 3022-3031. Yeung, E. C. and R. L. Peterson. 1971. Studies on the rosette plant Hieracium floribundum. I. Observations related to flowering and axillary bud development. Canadian Journal of Botany: Vol. 50, 1972. pp 73-78.
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