White hawkweed's fibrous roots and root crown are immediately under the soil surface and susceptible to heat damage from fire [28,42,71]. Powell  classified white hawkweed as having "low resistance to fire", which is defined as having less than 35% chance that 50% of the species population will survive or immediately reestablish after passage of a fire with an average flame length of 12 inches (30 cm).
Effects of fire on white hawkweed differed between moderate and high severity sites after wildfire in Grand Teton National Park, Wyoming. The Waterfalls Canyon fire was a mixed-severity summer wildfire in forest dominated by subalpine fir, Engelmann spruce, and lodgepole pine. White hawkweed persisted on moderately burned (more than 40% of canopy trees alive 1 year after fire) sites but was not present on severely burned (all trees killed and the aboveground portions of understory species consumed) sites until postfire year 3, where it increased in subsequent years 
White hawkweed's low resistance to fire causes an initial decrease in abundance. Kilgore  reveals
that frequency of white hawkweed decreased 1 and 2 years after prescribed burning in red fir (Abies
magnifica) forests of the Sierra Nevada. In giant sequoia-mixed conifer forests of the Sierra
Nevada, California, a decrease in white hawkweed occurred immediately following logging, piling, and
burning , though the effects of burning could not be separated from the effects of soil disturbance
caused by logging and piling. Similarly, shelterwood cutting and underburning on Douglas-fir, grand fir,
and western redcedar habitat types within the Priest River Experimental Forest and the Payette National
Forest in Idaho decreased the cover of white hawkweed, although probably not significantly (see table
below). After the shelterwood treatment a "moist fuels underburn" and a "dry fuels
underburn" were prescribed. The dry fuels burn reduced cover of white hawkweed more than
the moist fuels burn. On the unburned control white hawkweed increased slightly after the shelterwood
White hawkweed is a native, deciduous, perennial forb. Its erect stems (1 to several) arise from a fibrous rooted caudex that is immediately under the mineral soil surface. The stems are 0.5 to 4 feet (1.5-12 dm) tall. Basal and lowermost cauline leaves are persistent. The inflorescence is composed of 12 to 35 small flower heads in open cymes or panicles. The flower heads are made up of ray flowers. The fruit is a small, hard, one-seeded achene with a pappus [15,21,45,51,62,71,74,76,78,99].
Fire adaptations: Postfire regeneration of white hawkweed occurs mostly from seed. As an offsite colonizer [8,88,90], white hawkweed establishes "rapidly" on mineral soils exposed by fire because of the many wind-borne seeds it produces [28,42,71]. It is also known to establish from the soil seed bank after logging and burning . Vegetation sampling following the Waterfalls Canyon fire in Grand Teton National Park, Wyoming, suggests that white hawkweed survived moderate and low severity fire [11,28], possibly by sprouting from the caudex after aboveground parts were killed.
FIRE REGIMES: Communities where white hawkweed most frequently occurs are characterized by a variety FIRE REGIMES. Fire exclusion may create longer fire-return intervals in some of these communities, sometimes resulting in subsequent larger and higher-severity fires .
The following table provides fire return intervals for plant communities and ecosystems where white hawkweed is important. Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".Community or Ecosystem Dominant Species Fire Return Interval Range (years) grand fir Abies grandis 35-200  western larch Larix occidentalis 25-350 [5,13,23] Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to >200  whitebark pine* Pinus albicaulis 50-200 [1,3] Rocky Mountain lodgepole pine* P. contorta var. latifolia 25-340 [12,13,92] Sierra lodgepole pine* P. contorta var. murrayana 35-200 Jeffrey pine P. jeffreyi 5-30 western white pine* P. monticola 50-200 Pacific ponderosa pine* P. ponderosa var. ponderosa 1-47  interior ponderosa pine* P. ponderosa var. scopulorum 2-30 [4,10,63] Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [4,6,7] coastal Douglas-fir* P. menziesii var. menziesii 40-240 [4,72,82] Pacific coast mixed evergreen P. menziesii var. menziesii-Lithocarpus densiflorus-Arbutus menziesii <35-130 [4,16] California oakwoods Quercus spp. <35  coast live oak Q. agrifolia 2-75  canyon live oak Q. chrysolepis <35 to 200 Oregon white oak Q. garryana <35  California black oak Q. kelloggii 5-30  redwood Sequoia sempervirens 5-200 [4,33,91] western redcedar-western hemlock Thuja plicata-Tsuga heterophylla >200 mountain hemlock* Tsuga mertensiana 35 to >200  *fire return interval varies widely; trends in variation are noted in the species review
White hawkweed is not known to be used by livestock, though several wildlife species utilize it. White hawkweed leaves are slightly palatable and are eaten by Columbian black-tailed deer on southern Vancouver Island, British Columbia . White hawkweed is utilized by mule deer in California giant sequoia groves . In Nevada, deer and elk utilize white hawkweed from the time it comes up in the spring until it dries up in the fall . White hawkweed is preferred by elk in western Montana during early and late summer [30,66,67]. It is a grizzly bear food in southern Canada and the conterminous United States . In Oregon, white hawkweed seeds and seedlings are an important food source for the Oregon junco. Its seeds are also eaten by pine siskins [37,38].
Palatability/nutritional value: No information is available on this topic.
Cover value: No information is available on this topic.
White hawkweed is a dominant species in the western hemlock/salal (Tsuga heterophylla/Gaultheria
shallon)/white hawkweed plant association in the southern Oregon Cascades .
White hawkweed is susceptible to high levels of human trampling. A study from western Montana revealed
that white hawkweed has low (<10% increase) resilience in terms of short- and long-term recovery
of relative cover after being trampled. Its resistance is listed as moderate (200 to 400 passes/year
required to reduce frequency). It can tolerate light (75 to 100 passes/year) trampling and still
In British Columbia, white hawkweed is considered an invasive/weedy species that seeds into open
habitats . It is considered an invader species or a low-value meadow species, which increases with
overgrazing in the Sierra Nevada .
Seed banking: Some evidence suggests that white hawkweed occurs in the soil seed bank in some plant communities; however, information is lacking on the density and longevity of white hawkweed seeds in soil. Hamilton and Peterson  report that white hawkweed was stimulated to germinate from buried seed following logging and burning in British Columbia's sub-boreal spruce zone. A soil seed bank study was conducted on Douglas-fir (Pseudostuga menziesii) and grand fir (Abies grandis) habitats in central Idaho. Soil samples were exhumed from 0 to 2 inches (0-5 cm) and 2 to 4 inches (5-10 cm) and subsequently underwent greenhouse germination tests. Only 1 viable white hawkweed seed germinated from the 0- to 2-inch (0-5 cm) layer, and none from the 2 to 4 inches (5-10 cm) layer successfully germinated . In field and/or greenhouse germination studies, white hawkweed emerged from soil samples taken from forest and disturbed soils in southwestern British Columbia's coastal western hemlock zone. White hawkweed was observed among vegetation of the plots that the samples were taken from .
Germination: Information on germination requirements for white hawkweed is limited. White hawkweed seed collected from Yellowstone National Park underwent greenhouse germination studies. Seed was planted 1 month after seed was collected to mimic fall germination while other seed was planted after 2.5 months of cold storage to mimic spring germination. Total percent germination for fall conditions was 47.3% and total percent germination for spring conditions was 26.3%. In this study, cold storage reduced germination .
Seedling establishment/growth: White hawkweed readily establishes in burned or disturbed areas [71,79]. Occurrence on recently exposed mineral soil and open habitats suggests that it establishes well on exposed mineral soil and high light areas.
Vegetative regeneration: According to McLean  and Powell , white hawkweed lacks rhizomes or other means of vegetative reproduction. Conversely, Patterson and others  state that white hawkweed arises from a "short rhizome", and Halpern  reports a shallow "caudex-like rhizome". There is no additional evidence presented in the literature reviewed that white hawkweed regenerates vegetatively from rhizomes; however, some evidence suggests that it may sprout following top-kill [11,28].
White hawkweed is not shade-tolerant but is capable of surviving under some canopy cover. It is characteristic of disturbed areas [25,59] where percent cover increases during early successional stages and continues to increase (2 to 4 years) until eventually white hawkweed cover declines [42,43,65,68,70]. In British Columbia white hawkweed is characteristic of disturbed sites, commonly inhabits exposed mineral soil in early-seral communities, and is common in open-canopy forests . White hawkweed is more abundant in open areas of mixed conifer and white fir (Abies concolor) types of the Siskiyou Mountains of southwestern Oregon . In northern Idaho white hawkweed can occur in 0% to 100% tree canopy cover, but it is more frequently found in areas with 0% to 55% canopy cover .
White hawkweed has low cover values during early succession and increases 2 to 4 years after disturbance [8,29,53,86,88,90]. In the northern Rocky Mountains, white hawkweed is a secondary offsite colonizer that usually establishes the first postfire year [88,90]. As a wind-dispersed species, it was a pioneer and colonized widely on barren lahars and pumice sites within 2 to 3 growing seasons after the eruption of Mount St Helens in 1980 [24,44,93,101]. White hawkweed was also recorded on refugia and isolated pumice sites 18 years after the eruption. The pumice plots furthest from the refugia had the least cover of white hawkweed, suggesting that the wind-dispersed seeds of white hawkweed from refugia plants were responsible for colonizing the barren pumice sites . White hawkweed was a pioneer on Douglas-fir and subalpine fir (Abies lasiocarpa) environments following the 1988 Yellowstone fires, most likely from wind-dispersed seed, but possibly from the soil seed bank .Increase of white hawkweed in the first 8 years following logging in Douglas-fir forests of western Washington and Oregon  1926 1928 1930 1933 Percent cover 0.5 0.4 2.4 1.5 Frequency of occurrence 36 36 72 79