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Hieracium

See list of 17 species in this genus

Sell (1987) argued convincingly, on morphological grounds, for the segregation of Pilosella from Hieracium. Gaskin and Wilson (2007) showed that Pilosella is a monophyletic group. However, they also showed that recognition of Pilosella creates a paraphyletic Hieracium unless the genus Stenotheca, a genus of western hemisphere plants, is also recognized. The morphological distinction between Hieracium and Stenotheca is relatively weak and does not seem to justify generic separation. Therefore, the genus Hieracium is recognized here in the broad sense until such time as study elucidates morphological separation of Stenotheca from Hieracium. References: Voss (1996), Strother (2006c).

  • 1a. Cypsela body 1.2–2 (–2.2) mm long, each rib on the surface of the ovary projecting to form a crenulate apex [Fig. 422]; pappus bristles mostly 25–40 in 1 series [Fig. 422]; rays yellow, yellow with an red abaxial stripe, or orange-red; stems scapose, without leaves or with few and reduced leaves; leaves tapering to an ill-defined petiole; plants with a well-developed rosette of basal leaves at anthesis, commonly with stolons [Fig. 426]
    • 2a. Reproductive stems bearing a solitary capitulum or a capitulescence with 2–4 (–6) capitula on elongate peduncles (5–) 15–150 mm long [Fig. 426]; leaf blades 2–4 (–6) times as long as wide; plants 3–25 (–40) cm tall
      • 3a. Capitulescence with 1 or 2 (–3) capitula [Fig. 426]; involucres 7.5–9 (–10) mm tall; leaf blades densely pubescent with stellate hairs on the abaxial surface, the hairs usually contiguous and concealing the surface
      • 3b. Capitulescence with (1–) 2–4 (–6) capitula; involucres (9–) 10–13 mm tall; leaf blades moderately pubescent with stellate hairs on the abaxial surface, the hairs not so numerous as to be contiguous
    • 2b. Reproductive stems bearing (3–) 5–30 (–50) capitula, these usually in compact, corymb-like capitulescences on short peduncles 1–15 (–28) mm long; leaf blades 3–8 times as long as wide; plants (10–) 20–100 cm tall
      • 4a. Ray flowers orange-red (drying dark red); involucral bracts 1.5–3 mm wide
      • 4b. Ray flowers yellow; involucral bracts 0.5–1.25 mm wide
        • 5a. Involucres 7.5–9 mm tall; pappus bristles 4–5 (–6) mm long; ray corollas 8–12 mm long; leaf blades green, with abundant setae adaxially; plants with short or, more commonly, long rhizomes and often also short, prostrate stolons
        • 5b. Involucres 5–6 (–7) mm tall; pappus bristles 3–4 mm long; ray corollas 6–9 mm long; leaf blades glaucous, sparsely and unevenly setose to subglabrous adaxially; plants usually with short, praemorse rhizomes and also usually lacking prostrate stolons (sometimes with divergent to ascending branches)
          • 6a. Peduncles lacking stellate hairs or with very few stellate hairs; basal leaf blades lacking stellate-hairs on the abaxial surface, either glabrous or with simple, eglandular hairs; involucral bracts mostly 0.5–0.75 mm wide
          • 6b. Peduncles moderately to densely pubescent with stellate hairs; basal leaf blades sometimes with minute stellate-hairs on the abaxial surface (longer, simple, eglandular ones may be present as well); involucral bracts mostly 0.75–1 mm wide
  • 1b. Cypsela body (2–) 2.5–5 mm long, each rib apically confluent to form an obscure ring [Fig. 424]; pappus bristles mostly 30–60 (or more) in 2 series; rays yellow; stems scapose or evidently leafy; lower leaves usually tapering to a ± distinct petiole; plants with a basal 
rosette of leaves or these withered at anthesis, never with stolons

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