Your help is appreciated.    We depend on donations to help keep this site free and up to date for you. Can you please help us?

Pycnanthemum

See list of 6 species in this genus

Reference: Grant and Epling (1943).

  • 1a. Inflorescence congested but many of the branches within the clusters visible, especially in fruit [Fig. 702], the individual clusters 15–35 (–45) mm wide; calyx zygomorphic, the upper lip definitely shorter than the lower lip, the lobes tipped with a tuft of long, septate hairs
  • 1b. Inflorescence very dense, only the lowest branches, if any, visible [Fig. 703], the individual clusters 3–15 (–20) mm wide; calyx ± actinomorphic, the lobes lacking a tuft of long, septate hairs (though other hairs may be present)
    • 2a. Principal leaf blades lanceolate to ovate, 12–30 (–40) mm wide, mostly less than 
2.5 times as long as wide, rounded at the base, with a few low teeth on each margin
    • 2b. Principal leaf blades linear to lanceolate, 2–12 (–15) mm wide, mostly more than 2.5 times as long as wide, cuneate at the base, with or without teeth
      • 3a. Leaf blades 2–4 (–5.5) mm wide, sessile, glabrous [Fig. 703]; stem glabrous or rarely with a few upcurved hairs on the angles; calyx lobes 1–1.5 mm long
      • 3b. Leaf blades 3–12 (–15) mm wide, short-petioled to subsessile, pubescent on at least the abaxial surface; stem pubescent on the angles and sometimes the faces as well; calyx lobes 0.5–1 mm long (up to 1.5 mm long in P. torrei)
        • 4a. Bracts, and often also the leaf blades, pubescent on the adaxial surface with minute, soft hairs (view at 20 ×); stems pubescent on the faces as well as the angles
        • 4b. Bracts and leaf blades glabrous on the adaxial surface (sometimes with minute, stiff scabrules on the adaxial bract surface); stems pubescent primarily on the angles or also pubescent on the faces in P. torrei

Show All Couplets

 Show photos of:   Each photo represents one species in this genus.