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Montana Field Guides

Tall Hawkweed - Hieracium piloselloides
Other Names:  Hieracium florentinum, Pilosella piloselloides

Noxious Weed: Priority 2A
Non-native Species

Global Rank: GNR
State Rank: SNA
(see State Rank Reason below)

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 0

External Links






State Rank Reason (see State Rank above)
Hieracium piloselloides is part of the Meadow Hawkweed complex. Plants are native to Europe (FNA 2006). A conservation status rank is not applicable (SNA) because the plant is an exotic (non-native) in Montana that is not a suitable target for conservation activities.
 
General Description
PLANTS: Perennial forbs with erect stems from 15-40(70+) cm tall. Stems are single (simple). Stems have stiff hairs (hirsute) of 6-15+ mm long that may become shorter, 3-10+ mm, upwards. Upper stems sometimes have hairs. Source: FNA 2006.

LEAVES: 3-8+ basal leaves and 0-2(4+) stem leaves. Basal leaves 3-10(15+) cm long by 0.8-2.0+ cm wide and petiolate. Blades are lanceolate to oblanceolate, margins entire or denticulate, and tips rounded to acute. Leaf surfaces are usually glabrous, or sometimes on the midribs and margins have long, stiff hairs (hirsute). Leaf hairs are 1-4+mm long. Source: FNA 2006.

INFLORESCENCE: More-or-less umbelliform or in congested corymbiform arrays. Yellow flower heads of (3)10 to 30+ are pedunculate. Peduncles have several hair types: long, stiff (1-2+ mm), stellate (star-like), and stalked glands. The involucres are campanulate, 5–7 mm high. The involucral bracts (phyllaries) have several hair types (long, stiff (0.5-1.5 mm), stellate (star-like), and stalked glands) and acute to acuminate tips. Flower heads composed of (40)60-80+ florets with yellow petals, 6–9 mm long. The pappus is of white bristles occurring in 1-series and 3-4 mm long. Fruits (cypselae) are columnar, about 1.5 mm long, and retain the tuft of bristles (pappus). Source: FNA 2006.

Phenology
Flowering May-September (FNA 2006).

Diagnostic Characteristics
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 (asexually produced seeds).

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

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.

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.

Hieracium 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.

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.

Range Comments
Plants are native to Europe (FNA 2006). In the western U.S. plants are present from northwestern Montana to northern British Columbia with a possible occurrence in the Blue Mountain of Oregon (FNA 2006; www.pnwherbaria.org). Plants are present in eastern Canada south to the northeastern, southeastern, and midwestern portions of the U.S. (FNA 2006).

Observations in Montana Natural Heritage Program Database
Number of Observations: 2

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Disturbed sites (FNA 2006).

Management

References
  • Literature Cited AboveLegend:   View Online Publication
    • Flora of North America Editorial Committee. 2006. Flora of North America North of Mexico. Vol. 19. Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford Univ. Press, New York. xxiv + 579 pp.
    • Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Web Search Engines for Articles on "Tall Hawkweed"
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Citation for data on this website:
Tall Hawkweed — Hieracium piloselloides.  Montana Field Guide.  .  Retrieved on , from