Montana Field Guide

PLANTS: Perennial forbs with erect stems from 20-80 cm tall that are rhizomatous and sometimes have short stolons. Rhizomes have fibrous-roots. Stems are single (simple). Stems have stiff hairs (hirsute) of 1-4+ mm that may become shorter and stipitate-glandular upwards. Upper stems might also have stellate (star-like) hairs. Sources: FNA 2006; Lesica et al. 2012.

LEAVES: 3-8 basal leaves and 0-2 stem leaves. Basal leaves 3-15 cm long, petiolate, blades lanceolate to oblanceolate, margins entire to obscurely denticulate, and tips rounded to acute. Leaf surfaces with stiff hairs (hirsute) of 1-3+ mm long and stellate-pubescent.

INFLORESCENCE: More-or-less umbelliform or in congested corymbiform arrays. Yellow flower heads of 5 to 25, clustered, and pedunculate with stellate pubescence and stipitate-glandular hairs. The involucres are campanulate, 6–8 mm high. The involucral bracts (phyllaries) are linear-lanceolate with scarious-margins and acute to acuminate tips, stellate-hairy, hirsute, and densely black setose-glandular. Flower heads composed of 25 to 50 florets with yellow petals, 3–10 mm long. The pappus is of white bristles occurring in 1-series and 4-6 mm long. Fruits (cypselae) are columnar, about 1.5 mm long, and retain the tuft of bristles (pappus).

Flowering May to August (FNA 2006).

Montana has about 4 native and 3 exotic Hawkweeds. Their species identification can be complex and confusing because species interbreed to form hybrids and some populations are apomictic (see Reproductive Characteristics).

Hieracium caespitosum, Hieracium praealtum, Hieracium piloselloides, and Hiercium gracile have yellow flower heads while Hieracium aurantiacum is the only Hawkweed with red-orange flower heads.

Meadow Hawkweed (Hieracium caespitosum) has florets with pappus bristles in 1 series (single ring of bristles). Its upper stems and involucres have dense glandular setae (hairs), but Hieracium praealatum has scattered glandular setae mixed in with non-glandular setae (Lesica et al. 2012). Hieracium caespitosum has short stolons (when they are present). Hieracium praealatum is more likely to have stolons and when present they are longer and slender.

Kingdevil Hawkweed (Hieracium praealtum) Villers ex Gochnat has leaves with lower surfaces that have stellate (star-shaped) hairs (FNA 2006). In Lesica’s treatment in the Manual of Montana Vascular Plants (2012) our plants appear to better fit the description of Hieracium praealtum Villers ex Gochnatthen than of H. piloselloides Vill. or H. floribundum Wimm. & Grab. However, the Strother’s treatment in the Flora of North America (2006) does not include Hieracium praealtum Villers ex Gochnat, but does recognize it might merit taxonomic recognition.

Tall Hawkweed (Hiercium piloselloides) has leaves (upper and lower surfaces) that are lack both hair types of long, stiff hairs (piloso-hirsute) and stellate (star-like) hairs (FNA 2006). Leaves are glabrous or have one long, stiff hairs on the midribs and margins.

Alpine Hawkweed (Hiercium gracile)is a native plant of the subalpine and alpine habitats. Its florets have 2 series of pappus bristles. Plants also tend to be less than 30 cm tall.
* The type specimen for Hieracium floribundum (Pale Hawkweed) is likely a hybrid between Hieracium caespitosum and Hieracium lactucella (FNA 2006); therefore, the name should not be applied to specimens in Montana.

Grasslands and along roadsides from valleys to montane (Lesica et al. 2012).

The loss of biodiversity is the most prevalent threat posed by Meadow Hawkweed.

HABITAT VULNERABILITY
In their native habitats of northern and central Europe, Meadow and Orange Hawkweeds are species of pastures, roadsides, abandoned fields, and meadows that form small populations (Skalinksa 1967). In the northern U.S. these plants appear to pose the greatest threat to cooler, sub-humid to humid habitats. They have invaded moist pastures, forest meadows, abandoned fields, clearcuts, and roadsides from valleys to montane (Skalinksa 1967; Lesica et al. 2012). Once established plants quickly grow into a matt of dense rosettes (Wilson and Callihan in Sheley and Petroff 1999). Consequently, elk habitat, recreational areas, and pristine mountain meadows are especially susceptible to invasion (Wilson and Callihan in Sheley and Petroff 1999). Drier rangeland habitats are not suspected of being vulnerable (Wilson and Callihan in Sheley and Petroff 1999). Meadow and Orange Hawkweeds apparently do not survive in annually-tilled cropland (Wilson and Callihan in Sheley and Petroff 1999).

NUTRIENT VALUE
Meadow Hawkweed leaves and flower buds are eaten by livestock, deer, and elk (Wilson and Callihan in Sheley and Petroff 1999). The protein content of leaves ranged from 7% (similar to low-quality cured timothy hay) to 11% (equal to high-quality grass hay) (Callihan et al. 1995). The digestibility of Hawkweed leaves was 74% which is higher than the 60-65% found in pasture grass. Flowers were moderately digestible at 64% and contained twice (18%) the amount of protein as the leaves.

POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus ternarius, Bombus terricola, Bombus bohemicus, and Bombus flavidus (Heinrich 1976, Colla and Dumesh 2010).

Meadow Hawkweed plants reproduce by seed, rhizomes, and stolons.

From the rosette, plants produce 1 flowering stem. Plants are often apomictic, that is reproducing from asexually produced seeds (FNA 2006). Apomictic reproduction creates morphological variants that perpetuate at population and regional levels (FNA 2006). This can make identifying hybrids difficult. Very few seeds are produced sexually through pollination and out-crossing (Wilson and Callihan in Sheley and Petroff 1999). Flowering in a related species, Hieracium floribundum, was found to occur upon exposure to a specific amount and quality of light (Wilson and Callihan in Sheley and Petroff 1999).

Mature seeds can germinate immediately after dispersal and be viable for up to seven years (Wilson and Callihan in Sheley and Petroff 1999). In a study of Hieracium floribundum only 1% of new plants were born from seeds (Thomas and Dale 1974). The study also found that 80% of the seeds dispersed within the colony with only 1% of the seeds travelling greater than 30 feet (10 meters) from the patch. Another study found that seedlings that germinated in spring had better survival rates than those germinating in summer or winter (Johnson and Thomas 1978).

PREVENTION [Adapted from Wilson and Callihan in Sheley and Petroff 1999]
Successful management seeks to prevent infestations and detect them before the patch spreads vegetatively. Large infestations are difficult to control. Using multispectral, digital images may identify infestations in remote areas better than visual surveys over large areas (refer to Carson et al. 1995).

CHEMICAL CONTROL [Adapted from Wilson and Callihan in Sheley and Petroff 1999]
The Phenoxy-type herbicides (2,4-D, clopyralid, and picloram) are effective in controlling orange and meadow Hawkweeds when applied to the rosette stage and used with a surfactant. The herbicide type and concentration, timing of chemical control, soil properties, and other factors will determine its effectiveness and impact to non-target species. Strict adherence to application requirements defined on the herbicide label will reduce risks to human and environmental health. Many herbicides must be applied by applicators with an Aquatic Pest Control license. Consult your County Extension Agent and/or Weed District for more information on herbicidal control.

Researchers at the University of Idaho found more than a 50% control of Hawkweed using clopyralid at the rate of 0.5 lb ai/ac. A similar control was found using picloram at the rate of 0.2-0.5 lb ai/ac.

A combination of fertilizers and herbicides used where Hawkweed is mixed with perennial grasses, legumes, and other forbs can contain spreading. Fertilizer treatments reduced Hawkweed density and vigor in the U.S., Canada, and New Zealand. Depending upon soil productivity and grass condition, fertilizers can promote the growth of desirable plants which may become competitive enough to suppress Hawkweed growth.

CULTURAL & GRAZING CONTROLS [Adapted from Wilson and Callihan in Sheley and Petroff 1999]

Hand-pulling and mowing are not effective control measures. Physical disturbance to meadow Hawkweed severs roots, stolons, and/or rhizomes causing the plant to further spread. Mowing may remove flowering stems and reduce seed production but will not hinder growth by the stolons or rhizomes. Soils disturbed by livestock, rodents, or people can also enhance the plant to spread.

BIOCONTROL [Adapted from Wilson and Callihan in Sheley and Petroff 1999]
In 1995 the USDA Agricultural Research Service in Bozeman, Montana began to develop the feasibility of a biological control program for Orange and Meadow Hawkweeds. However, biological control for these plants has not yet successfully been developed in the U.S.

Useful Links:
Montana Invasive Species website
Montana Biological Weed Control Coordination Project
Montana Department of Agriculture - Noxious Weeds
Montana Weed Control Association
Montana Weed Control Association Contacts Webpage.
Montana Fish, Wildlife, and Parks - Noxious Weeds
Montana State University Integrated Pest Management Extension
Weed Publications at Montana State University Extension - MontGuides

The loss of biodiversity is the most prevalent threat posed by Meadow Hawkweed.