Evening-primrose Family

Oenothera

1 Fruit indehiscent; seeds 1-6 per capsule, 1.5-3.5mm long ....................................................................................................... Biennial Gaura
1 Fruit dehiscent; seeds (10-) 50-many per capsule, 0.3-2mm long.
  2 Ovary essentially terete; fruit terete or with 4 rounded ridges; stamens equal in length (except in Pink Evening-primrose).
   3 Flowers white or pink; flower buds nodding ....................................................................................................... Pink Evening-primrose
   3 Flowers yellow; flower buds erect.
    4 Fruit linear, nearly same width through its length; seeds borne ascending in locules, rounded or fusiform, more or less regularly pitted.
      5 Non-flowering portion of stems stiff, densely strigillose or sometimes also villous; leaves gray-green, densely strigillose, usually
        subentire to shallowly dentate (rarely lyrate); [maritime situations] ..................................................... Seaside Evening-primrose
      5 Non-flowering portion of stem not stiff, moderately to sparsely strigillose to sometimes densely villous, and also ± glandular
        puberulent; leaves green, sparsely to moderately strigillose and usually villous, deeply lobed to dentate (rarely some of them
        subentire); [inland disturbed situations].
        6 Petals 2.5-4cm long; style 4-7.5cm long; stigma lobes well elevated above anthers at anthesis ...........Showy Evening-primrose
        6 Petals 0.5-2.2cm long; style 2-5cm long; stigma lobes surrounded by anthers at anthesis ...........Cut-leaved Evening-primrose
    4 Fruit thickest near base, tapering to apex; seeds borne horizontally in locules, angled-prismatic, not regularly pitted.
      7 Stigma elevated above anthers at anthesis; petals 2.5-5cm long .............................................. Large-flowered Evening-primrose
      7 Stigma surrounded by or below anthers at anthesis; petals 0.7-2.5(-3)cm long.
        8 Plant appearing exclusively appressed-pubescent (as seen without magnification).
          9 Apex of inflorescence curved; free sepal tips subterminal in bud, erect to spreading; dry capsules usually rusty brown .................
            ............................................................................................................................................................ Oakes's Evening-primrose
          9 Apex of inflorescence erect; free sepal tips erect in bud; dry capsules gray-green or dull green ...Common Evening-primrose
        8 Plant appearing either glabrous or with a mixture of long pustular hairs and appressed pubescence (as seen without magnification).
          10 Apex of inflorescence curved; free sepal tips subterminal in bud .................................................. Oakes's Evening-primrose
          10 Apex of inflorescence erect; free sepal tips terminal or subterminal in bud ............................... Common Evening-primrose
  2 Ovary 4-angled or 4-winged (at least near its tip); fruit sharply 4-angled or 4-winged; stamens of two lengths.
    11 Petals 5-10mm long; inflorescence usually nodding ....................................................................................... Little Evening-primrose
    11 Petals 15-30mm long; inflorescence usually erect ......................................................................... Narrow-leaved Evening-primrose