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Key to Asclepias, Key D: milkweeds with milky sap, with petiolate, nonlinear leaves, in flower

Apocynaceae

Asclepias

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(c) Griffith, Floyd A.
1 Corolla (not the corona) greenish, either pale green or yellowish green.
(c) Ward, Scott G
  2 Leaves subopposite (to alternate upwards); corolla lobes 7-17 mm long.
    3 Corolla lobes 7-12 mm long; leaves mostly 4-7× as long as wide, acuminate at the apex; [e. OK and e. TX and westwards]
    3 Corolla lobes 13-17 mm long; leaves mostly 2-4× as long as wide, obtuse at the apex; [c. TX and c. OK and eastwards]
(c) Ward, Scott G
  2 Leaves opposite; corolla lobes 6-10 mm long.
      4 Hoods greatly exceeding the gynostegium, tubular in shape, green to bronze and white to cream apically; [TX, OK, & LA westward and southward].
        5 Hoods 3.5-5 mm long; horn apices unilobed to bluntly emarginate; horns enclosing the tips of the hoods; corolla lobes 5-7 mm long
        5 Hoods 7-10 mm long; horn apices prominently and deeply bilobed; horns closely appressed to the interior of the hoods for most of their length, not closing the tips of the hoods; corolla lobes (7-) 8-14 mm long
      4 Hoods shorter than or only slightly exceeding the gynostegium, conduplicate to laminar in shape, colors various; [collectively widespread].
          6 Corolla lobes strongly reflexed and appressed to the pedicel along their entire lengths; hoods closely appressed to the gynostegium; horns absent
          6 Corolla lobes reflexed with spreading tips (if contacting the pedicel as in A. arenaria, then the lobes not closely appressed to the pedicel to their tips); hoods not closely appressed to gynostegium; horns present and exserted.
             7 Hoods greenish-cream, cream, or green [collectively widespread].
               8 Hoods exceeding gynostegium; leaves thick and leathery (coriaceous), tomentose to glabrate; petioles 7-17 mm long; stems 1-8, tomentose; [w. Gulf Coastal Plain in TX and OK westward]
               8 Hoods shorter than gynostegium; leaves thin and papery (chartaceous), puberulent to tomentulose; petioles 2-9 mm long; stems 1 (-2), densely puberulent; [NC to FL peninsula, disjunct in e. TX]
                 9 Petals curved, the tips spreading away from the pedicel; [NC to FL peninsula]
             7 Hoods yellow-bronze or white, if white then with a green to purple stripe on the outer surface; [Coastal Plain].
                   10 Hoods white with a purple to green stripe on outer surface; gynostegium 0.5-1 mm long; calyx lobes lanceolate, glabrous, 2-3 mm long; [ne. FL to s. peninsular FL]
                   10 Hoods yellow-bronze; gynostegium 1-1.5 mm long; calyx lobes elliptic, hirtellous, 5-6 mm long; [Coastal Plain from SC to AR, OK, & TX]
(c) Bradley, Keith
(c) Cressler, Alan M.
1 Corolla (NOT the corona) pink, purple, crimson, orange, or white (sometimes pale green to greenish-white in A. exaltata.
                     11 Hoods distinctly longer than the anther heads; horns 0.5-1× as long as the hood, not conspicuously exserted beyond the hood.
                       12 Lower leaf surface glabrous to sparsely pubescent along the midvein only.
                          13 Hood opening very oblique, the hood therefore scoop-shaped, and also with 2 prominent lateral teeth; corolla pink to greenish (rarely white); plants 2-5 dm tall
                          13 Hood opening truncate and constricted, and lacking prominent teeth; corolla white (often pink or deep red at the "waist"); plants 3-12 dm tall
                       12 Lower leaf surface densely pubescent over the surface.
                            14 Hoods 9-15 mm long, narrowing abruptly to a long- attenuate apex; [MO, c. OK, & TX westward]
                            14 Hoods 4-6 mm long, the apices obtuse to acute and not abruptly narrowing; [widespread].
                              15 Corolla purplish-rose; the inner bases of the hood rounded or irregular but not toothed; umbels terminal and extra-axillary; leaves with 1-2 stipular colleters on each side of petioles, the abaxial surfaces sparsely pilosulous; plants 4-10 dm tall
                              15 Corolla rose or greenish-white; the inner bases of the hood toothed; inflorescence extra-axillary; leaves with 1-5 stipular colleters on each side of petioles, the abaxial surfaces tomentose to glabrate; plants (5-) 8-20 dm tall
                     11 Hoods about as long as the anther heads; horns 1-2× as long as the hood, exserted slightly to well beyond the hood.
                                16 Hood opening truncate, the hood therefore beaker-shaped; corolla lobes 8-12 mm long; [primarily of mesic forests of the Mountains]
                                16 Hood opening very oblique, the hood therefore scoop-shaped; corolla lobes 2.5-10 mm long; [primarily of wetlands of various provinces].
                                  17 Corolla bright orangey red, the lobes 5-10 mm long; corona orangey yellow; gynostegium orangey yellow
                                  17 Corolla white, pink, rose, or purple, the lobes 2.5-6 mm long; corona white, pink, or rose; gynostegium white or pale pink.
                                    18 Plants 3-9 dm tall; corolla lobes usually white (rarely slightly pink); corona white; leaves glabrous to sparsely puberulent beneath.
                                       19 14 Follicles pendulous on deflexed pedicels; leaves oval, oblong, or elliptic, 5-14 cm long; [wetlands on the Coastal Plain from SC to se. TX, inland to IN & IL]
                                       19 Follicles erect on erect pedicels; leaves ovate, lanceolate, or elliptic, 2-7 cm long; [canyons and mesic forests in c. and w. TX southward]
                                    18 Plants 5-15 dm tall; corolla lobes rose to purple (rarely white); corona pink or rose; leaves pubescent to glabrate beneath.
                                         20 Stems and leaves moderately to densely pubescent; leaves broader, the base rounded to subcordate, the apex acute to short-acuminate; plants usually relatively strict
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Key to Asclepias, Key E: milkweeds with milky sap, with petiolate, nonlinear leaves, in fruit (or sterile)

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1 Leaves subopposite
1 Leaves opposite (or apparently whorled in A. quadrifolia).
    3 Follicle pendant; seeds without a coma; [of swamp forests of SC and southward]
    3 Follicle erect; seeds with a coma; [collectively widespread].
      4 Leaf-bearing nodes 3-4, the upper and lower opposite, the middle with a whorl of 4 leaves
      4 Leaf-bearing nodes 3-many, all opposite.
        5 Follicle slightly to strongly muricate
          6 Leaf blades lanceolate to ovate or oblong, 2-14 cm wide; petioles tomentose to pilose; follicle apex long-acuminate; [MO, TX, & c. OK westward]
             7 Lower leaf surface glabrous, or pubescent on the midrib only.
               8 Leaves 3-11 cm wide; leaf blades broadly ovate to oblong or elliptic; follicles 12-14 cm long
               8 Leaves 0.5-3 cm wide; leaf blades elliptic, ovate, lanceolate or linear; follicles 6-13 cm long.
                 9 Stems pilosulous in a line or glabrate; leaf blades elliptic or oval to linear; follicles 6-10 mm long; [widespread exotic in disturbed areas]
                 9 Stems puberulent in a line; leaf blades ovate to lanceolate or elliptic; follicles 9-13 mm long; [native in canyons, moist woods, and hillsides in c. & w. TX southward]
                   10 Leaves lanceolate to lance-ovate, 4-10× as long as wide.
                     11 Leaves coriaceous, 3-10 cm long, 1.5-4.5 cm wide; [of dry upland situations]
                     11 Leaves herbaceous, 6-15 cm long, 2-7 cm wide; [of moist to wetland or dry situations].
                       12 Plants 0.6-3 dm tall; petioles puberulent; follicles lance-ovoid; coma 2.5-3.5 cm long; [dry habitats of c. and s. TX southward]
                       12 Plants 3-15 dm tall; petioles pilosulous to pilose; follicles fusiform; coma 1.5-2 cm long; [widespread in moist to wet habitats].
                          13 Stems and leaves sparsely pubescent to glabrescent; leaves narrow, the base obtuse to truncate, the apex long-acuminate; plants usually much branched
                          13 Stems and leaves moderately to densely pubescent; leaves broader, the base rounded to subcordate, the apex acute to short-acuminate; plants usually relatively strict
                   10 Leaves ovate to elliptic, 1.5-4× as long as wide.
                            14 Stem moderately to densely pubescent; plants 1.5-5 (-7) dm tall; [of xeric pinelands and plains of the Coastal Plain of from NC to s. FL, west to OK, AR, and TX].
                                16 Leaf bases rounded, truncate, or subcordate; leaf surfaces tomentose to glabrate; follicles pilosulous; plants 2-10 dm tall
                            14 Stem glabrous to pubescent in lines only; plants 2-12 dm tall; [collectively of various habitats throughout our area].
                                    18 Lower leaf surface glabrous or slightly pubescent; [of moist or dry habitats].
                                         20 Leaves with subcordate, truncate, or broadly rounded bases; [ne. FL to s. peninsular FL]
                                         20 Leaves with cuneate or rounded bases; [widespread in our area, but not ne. FL and peninsular FL]