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Key to Epilobium

Onagraceae

Epilobium

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1 Annual herbs from a taproot; epidermis of the lower stem exfoliating; [section Xerolobium]
1 Perennial herbs from a woody caudex, often also with above-ground stolons, basal offsets with rosette leaves, or rhizomes; epidermis of the lower stem tight; [section Epilobium].
  2 Larger leaves on a plant < 9 mm wide (to 19 mm in Epilobium palustre); teeth 0-7 per leaf-side; plants 1-9.5 dm tall
    3 Pubescence of the main stem densely villous, the hairs spreading; vestiture of the leaf upper surfaces villous
    3 Pubescence of the main stem strigillose (fine and appressed); vestiture of the leaf upper surfaces strigillose-puberulent (appressed) to glabrous.
      4 Leaf blades 1-7 mm wide; leaf upper surfaces densely strigillose-puberulent; inflorescence erect to arching in bud (later erect)
      4 Leaf blades 2-19 mm wide; leaf upper surfaces glabrous or nearly so; inflorescence nodding in bud (later erect)
  2 Larger leaves on a plant > 10 mm wide; teeth (8-) 15-75 per leaf-side; plants 1-12 (-25) dm tall
        5 Stigma deeply 4-lobed; petals either 9-20 mm long, or 4-9 mm long; plants perennating by short or long, thick stolons terminating in basal rosettes; [exotic].
          6 Petals 9-20 mm long, shallowly notched at the apex; leaves (all) sessile and slightly clasping the stem; plants perennating by long (to 1 m), thick, ropelike stolons
          6 Petals 4-9 mm long, deeply notched at the apex; leaves either short-petiolate (low on the stem) or sessile to subsessile (higher on the stem), not clasping the stem; plants perennating by short offsets
        5 Stigma capitate; petals 2-8 mm long; plants perennating either by basal offsets from the caudex, by basal turions, and/or by threadlike, aboveground stolons terminating in turions.
             7 Mature coma (attached to plump seeds) cinnamon brown (paler when immature); seed surfaces papillose (the papillae sometimes forming weak lines); inflorescence axes with eglandular strigillose hairs only; petals 2.5-5.5 mm long, white (sometimes whitish-pink).
             7 Mature coma white or dingy; seed surfaces with well-developed papillae arranged conspicuously in lines; inflorescence axes usually with a mixture of eglandular and glandular strigillose hairs; petals 2-12 (-14) mm long, pink, rose, or white.
               8 Herbs with basal rosettes; petals 2-6 (-9) mm long, white (sometimes pink)
               8 Herbs with large (5-12 mm long) turions borne 1-10 cm below the ground's surface; petals 4.5-12 (-14) mm long, rose or pink (rarely white)