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White Hawkweed

Hieracium albiflorum Hook.

Description

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Plants 15–40(–90) cm. Stems proximally usually piloso-hirsute (hairs 1–6+ mm), rarely glabrous, distally glabrous. Leaves: basal (0–)3–8+, cauline 1–5(–12+); blades oblanceolate, 40–100(–300) × 12–30(–60+) mm, lengths 3–5+ times widths, bases cuneate, margins usually entire, sometimes sinuately toothed, apices obtuse to acute, faces piloso-hirsute (hairs 1–6 mm), rarely glabrous. Heads (3–)12–50+ in corymbiform to paniculiform arrays. Peduncles usually glabrous, sometimes stipitate-glandular. Calyculi: bractlets 5–12+. Involucres ± campanulate, (7–)8–10(–11) mm. Phyllaries 8–13+, apices acuminate, abaxial faces piloso-hirsute (hairs 1–2+ mm), stellate-pubescent, and stipitate-glandular. Florets (6–)12–25+; corollas yellow, 9–10 mm. Cypselae columnar, 2.5–4 mm; pappi of 30–40+, stramineous bristles in ± 2 series, (4–)5–7 mm.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 19: 281, 282, 288, 292 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of North America @ eFloras.org
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Flora of North America Editorial Committee
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Synonym

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Chlorocrepis albiflora (Hooker) W. A. Weber
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cc-by-nc-sa-3.0
copyright
Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 19: 281, 282, 288, 292 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
source
Flora of North America @ eFloras.org
editor
Flora of North America Editorial Committee
project
eFloras.org
original
visit source
partner site
eFloras

Broad-scale Impacts of Fire

provided by Fire Effects Information System Plants
More info for the terms: forest, root crown, severity, wildfire

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 [79] 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 [28]

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cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Broad-scale Impacts of Plant Response to Fire

provided by Fire Effects Information System Plants
More info for the terms: cover, fire use, forest, frequency, prescribed fire

White hawkweed's low resistance to fire causes an initial decrease in abundance. Kilgore [58] 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 [57], 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
treatment [86].

Percent cover of white hawkweed before and
after shelterwood treatment and subsequent underburning [86]
 
No burn
Moist burn (June)
Dry burn (September)
Pretreatment
1.6
1.5
1.6
Posttreatment
(1 year after burning)
1.8
1.3
0.5

White hawkweed readily establishes on soils exposed by fire on sites where it did not previously
occur. White hawkweed was among pioneer species in a whitebark pine community in the Bob Marshall
Wilderness, Montana after a stand-replacing, lightning caused fire; and after the lightning caused,
high-severity Sundance fire in northern Idaho's western redcedar-western hemlock forest type [8,88].
After studying Douglas-fir forests in western Washington, Kienholz [56] reported that white hawkweed
was not found in undisturbed forest but was abundant on mineral soil exposed by disturbance or severe
fire. White hawkweed did not occur on study sites before (1962) clearcut logging and burning
treatments and was not present on sites after logging but before burning (1963) in old-growth Douglas-fir
forests in the western Cascade Mountains, Oregon. Percent cover and frequency were recorded during each
of the 5 growing seasons following clearcut logging and broadcast slash burning, as shown in the table
below. By the fifth growing season, white hawkweed was reported as an important species [29].

Progression of white hawkweed abundance during
the first 5 growing seasons following clearcut logging and broadcast slash
burning in Douglas-fir forests in the Cascade Mountains [29]
Years after burning
1
2
3
4
5
Percent cover
<0.05
0.4
0.6
2.0
3.6
Percent frequency
0.9
4.4
11.3
16.0
25.7


Similar findings were reported from British Columbia's Sub-boreal Spruce and Engelmann
spruce-subalpine fir zones. White hawkweed was not recorded on pre-logged sites; it appeared in
early seral communities following clearcut logging and subsequent slash burning [46,47,48,49].
Spring and fall burning were executed on one study site; white hawkweed cover and frequency were
significantly (P<0.02) higher in spring versus fall burn plots [49].

Hamilton's Research Papers (Hamilton 2006a, Hamilton 2006b)
provide further information on prescribed fire use and postfire response of many plant species
including white hawkweed.The following Research Project Summary also provides information on prescribed fire use and postfire response of many
plant species, including white hawkweed:

Understory recovery after low- and high-intensity fires in northern Idaho
ponderosa pine forests

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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Common Names

provided by Fire Effects Information System Plants
white hawkweed

white flowered hawkweed
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cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Conservation Status

provided by Fire Effects Information System Plants
Information on state-level noxious weed status of plants in the United States is available at Plants Database.
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cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Description

provided by Fire Effects Information System Plants
More info for the terms: achene, caudex, forb, fruit, pappus

This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available [15,20,21,27,39,50,51,52,55,99,100].

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].

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cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Distribution

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More info for the term: forb

White hawkweed is a native perennial forb occurring throughout western North America. Populations are found from southeastern Alaska to Saskatchewan and south to California, Colorado, and northern Mexico [20,21,50,51,62,99]. Disjunct populations occur in Wisconsin and Quebec [34,96]. Flora of North America  provides a distributional map of white hawkweed.
license
cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Fire Ecology

provided by Fire Effects Information System Plants
More info for the terms: caudex, fire exclusion, fire regime, seed, severity

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 [49]. 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 [4].

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 [4] western larch Larix occidentalis 25-350 [5,13,23] Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to >200 [4] 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 [4] 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 [4] coast live oak Q. agrifolia 2-75 [40] canyon live oak Q. chrysolepis <35 to 200 Oregon white oak Q. garryana <35 [4] California black oak Q. kelloggii 5-30 [77] redwood Sequoia sempervirens 5-200 [4,33,91] western redcedar-western hemlock Thuja plicata-Tsuga heterophylla >200 mountain hemlock* Tsuga mertensiana 35 to >200 [4] *fire return interval varies widely; trends in variation are noted in the species review
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Fire Management Considerations

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More info for the term: severity

Literature to date, 2007, provides no clear direction for the use of fire in managing white hawkweed. As detailed above, it is possible for white hawkweed to survive low to moderate severity fires, but it is generally a poor survivor. It can rapidly colonize exposed mineral soils on burned sites via windborne seeds. Fire has both positive and negative impacts on populations of white hawkweed. The use of fire as a management tool need not be ruled out in the process of managing the habitats in which white hawkweed occurs.
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cc-publicdomain
bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Growth Form (according to Raunkiær Life-form classification)

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More info on this topic.

More info for the term: hemicryptophyte

RAUNKIAER [81] LIFE FORM:
Hemicryptophyte
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Habitat characteristics

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More info for the term: forest

White hawkweed is a common montane species [101]. In British Columbia, white hawkweed occurs on exposed mineral soils and soils with moderately dry to "fresh" (need for water exceeds supply) moisture regimes within boreal, cool temperate, and mesothermal climates. It predominantly inhabits temporarily or regularly disturbed areas [59]. On the Gifford Pinchot National Forest, Washington, white hawkweed is an indicator of warm, dry sites [94].

Site descriptions for white hawkweed State, Region, or Province Site characteristics California dry forests; 0 to 9,500 feet (0-2,900 m) [51] and
dry, open wooded slopes below 9,700 feet (3,000 m) [74] Colorado 7,000 to 10,500 feet (2,100-3,200 m) [50] Montana dry, open habitats from foothills to openings in subalpine forests [62] Nevada 5,800 to 8,500 feet (1,800-2,600 m) [55] Utah 6,500 to 11,000 feet (2,000-3,400 m) [99] Wyoming woods and slopes [27] Black Hills, South Dakota woods and slopes [26] Intermountain West open woods and open hillsides; 6,500 to 11,000 feet (2,000-3,400 m) [21] Mt Rainier National Park, Washington open slopes; 2,000 to 6,500 feet (610-2,000 m) [87] Uinta Basin, Utah 8,200 to 11,000 feet (2,500-3,400 m) [39] Yukon along dirt mining exploration road on mountain slope [17]
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Habitat: Cover Types

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

SAF COVER TYPES [32]:




205 Mountain hemlock

206 Engelmann spruce-subalpine fir

207 Red fir

208 Whitebark pine

210 Interior Douglas-fir

211 White fir

212 Western larch

213 Grand fir

215 Western white pine

218 Lodgepole pine

224 Western hemlock

227 Western redcedar-western hemlock

228 Western redcedar

229 Pacific Douglas-fir

230 Douglas-fir-western hemlock

233 Oregon white oak

234 Douglas-fir-tanoak-Pacific madrone

237 Interior ponderosa pine

243 Sierra Nevada mixed conifer

244 Pacific ponderosa pine-Douglas-fir

245 Pacific ponderosa pine

246 California black oak

247 Jeffrey pine

249 Canyon live oak

255 California coast live oak
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Habitat: Ecosystem

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

ECOSYSTEMS [36]:




FRES20 Douglas-fir

FRES21 Ponderosa pine

FRES22 Western white pine

FRES23 Fir-spruce

FRES24 Hemlock-Sitka spruce

FRES25 Larch

FRES26 Lodgepole pine

FRES27 Redwood

FRES28 Western hardwoods
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Habitat: Plant Associations

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More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: forest, shrub

KUCHLER [61] PLANT ASSOCIATIONS:




K001 Spruce-cedar-hemlock forest

K002 Cedar-hemlock-Douglas-fir forest

K004 Fir-hemlock forest

K005 Mixed conifer forest

K007 Red fir forest

K008 Lodgepole pine-subalpine forest

K010 Ponderosa shrub forest

K011 Western ponderosa forest

K012 Douglas-fir forest

K013 Cedar-hemlock-pine forest

K014 Grand fir-Douglas-fir forest

K015 Western spruce-fir forest

K016 Eastern ponderosa forest

K017 Black Hills pine forest

K018 Pine-Douglas-fir forest

K026 Oregon oakwoods

K028 Mosaic of K002 and K026

K029 California mixed evergreen forest

K030 California oakwoods
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Habitat: Rangeland Cover Types

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More info on this topic.

This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the terms: cover, shrubland, woodland

SRM (RANGELAND) COVER TYPES [85]:




109 Ponderosa pine shrubland

110 Ponderosa pine-grassland

202 Coast live oak woodland



ALASKAN RANGELANDS

None
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Immediate Effect of Fire

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More info for the term: severity

White hawkweed is likely top-killed by fire. Individual plants may survive low to moderate severity fire [11,28].
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Importance to Livestock and Wildlife

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More info for the term: cover

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 [19]. White hawkweed is utilized by mule deer in California giant sequoia groves [64]. In Nevada, deer and elk utilize white hawkweed from the time it comes up in the spring until it dries up in the fall [41]. 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 [22]. 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.

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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Key Plant Community Associations

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More info for the term: association

White hawkweed is a component in giant sequoia (Sequoiadendron giganteum) groves in California [64,84].

White hawkweed is a dominant species in the western hemlock/salal (Tsuga heterophylla/Gaultheria
shallon)/white hawkweed plant association in the southern Oregon Cascades [9].

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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Life Form

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More info for the term: forb

Forb
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Management considerations

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More info for the term: cover

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
recover [18].


In British Columbia, white hawkweed is considered an invasive/weedy species that seeds into open
habitats [49]. It is considered an invader species or a low-value meadow species, which increases with
overgrazing in the Sierra Nevada [80].

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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Phenology

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Flowering dates for white hawkweed State or Region Anthesis Period California June to August [74] Idaho June to August [76] Montana June to early September [62] Nevada June to August [55] Oregon June to August [95] Baja California June to August [100] Intermountain West June to August [21] Pacific Northwest June to August [20] Uinta Basin, Utah mid-July to early September [39]
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Plant Response to Fire

provided by Fire Effects Information System Plants
More info for the terms: cover, frequency, seed

White hawkweed initially decreases after passage of fire. Powell [79] categorizes its response to fire as "medium" in that it will likely regain pre-burn frequency or cover in 5 to 10 years. White hawkweed is an offsite colonizer [8,88,90] and establishes "rapidly" on burned plots via windborne seeds [28,42,71]. Its windborne seed allows it to establish in burned or disturbed areas where it did not previously occur.
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Post-fire Regeneration

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More info for the terms: ground residual colonizer, secondary colonizer, seed

POSTFIRE REGENERATION STRATEGY [89]:
Ground residual colonizer (on-site, initial community)
Secondary colonizer (on-site or off-site seed sources)
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Regeneration Processes

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More info for the terms: density, forest, seed, top-kill

White hawkweed's principal means of reproduction is through recruitment of windborne seed [42,71]. It readily establishes from seed in burned or disturbed areas [71,79].

Pollination: Access to nectaries and/or pollen of white hawkweed flowers is structurally restricted [75].

Breeding system: White hawkweed is self-fertile [21].

Seed production: White hawkweed produces "many" seeds [28,42,71].

Seed dispersal: White hawkweed seed is wind-dispersed. The light-weight, plumed achenes can be dispersed long distances [35,42].

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 [49] 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 [60]. 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 [69].

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 [83].

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 [71] and Powell [79], white hawkweed lacks rhizomes or other means of vegetative reproduction. Conversely, Patterson and others [76] state that white hawkweed arises from a "short rhizome", and Halpern [42] 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].

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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Regional Distribution in the Western United States

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

BLM PHYSIOGRAPHIC REGIONS [14]:




1 Northern Pacific Border

2 Cascade Mountains

3 Southern Pacific Border

4 Sierra Mountains

5 Columbia Plateau

6 Upper Basin and Range

7 Lower Basin and Range

8 Northern Rocky Mountains

9 Middle Rocky Mountains

10 Wyoming Basin

11 Southern Rocky Mountains

12 Colorado Plateau

13 Rocky Mountain Piedmont

15 Black Hills Uplift

16 Upper Missouri Basin and Broken Lands
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

States or Provinces

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(key to state/province abbreviations)
UNITED STATES AK CA CO ID MT NV OR SD UT WA WI WY
CANADA AB BC NT PQ SK YK
MEXICO Chih. Son.
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Successional Status

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More info for the terms: cover, eruption, frequency, seed, succession, tree

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 [59]. White hawkweed is more abundant in open areas of mixed conifer and white fir (Abies concolor) types of the Siskiyou Mountains of southwestern Oregon [31]. 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 [73].

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 [35]. 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 [2].

Increase of white hawkweed in the first 8 years following logging in Douglas-fir forests of western Washington and Oregon [53]   1926 1928 1930 1933 Percent cover 0.5 0.4 2.4 1.5 Frequency of occurrence 36 36 72 79
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Synonyms

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Chlorocrepis albiflora (Hook.) Weber [97,98]
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Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Taxonomy

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The scientific name of white hawkweed is Hieracium albiflorum Hook. (Asteraceae)
[20,21,27,39,51,52,54,62,99,100].
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html

Value for rehabilitation of disturbed sites

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White hawkweed is characteristic of disturbed areas [25,59]. Its ability to rapidly colonize disturbed areas [71,79] suggests that it has value for rehabilitation of disturbed sites; however, no information is available on this topic.
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bibliographic citation
Reeves, Sonja L. 2006. Hieracium albiflorum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/hiealb/all.html