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Key to Asclepias, Key B: milkweeds with milky sap, with linear leaves opposite, subopposite, whorled, or less typically, alternate

Apocynaceae

Asclepias

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(c) Ward, Scott G
(c) Ward, Scott G
(c) Cressler, Alan M.
1 Leaves either mostly in whorls of 3-6 (sometimes some nodes with merely opposite leaves), or subopposite (the leaves more-or-less paired but separated by 0.5-3 mm); corolla whitish, greenish, or creamy yellow, often suffused with rose-purple (especially at the tips of the corolla lobes).
  2 Leaves mostly in whorls of 3-6 (sometimes some nodes with merely opposite leaves); leaves 1.5-3 cm long, 0.5-4 mm wide; seeds 5-8 mm long, the coma ca. 2.5 cm long; milky sap often difficult to show (in living plants).
    3 Stems 1-8 from ground level, typically bearing sterile vegetative branchlets at some nodes at least; leaves glabrous; corona segments with entire margins; [TX and MO westward]
    3 Stems 1 (-3) from ground level, lacking sterile vegetative branchlets; leaves puberulent on the upper surface; corona segments with toothed or lobed margins; [widespread]
  2 Leaves subopposite (the leaves more-or-less paired but separated by 0.5-3 mm); leaves (3-) 5-18 cm long, (1-) 2-10 mm wide; seeds 7-11 mm long, the coma 3-5 cm long; milky sap obvious and profuse (in living plants).
      4 Leaf blades strongly conduplicate (folded lengthwise along the midvein, making a V cross-section).
        5 Stems glabrous; plants 40-170 cm tall; leaves drooping; corollas creamy yellow to greenish or cream colored adaxially, tan to reddish-brown abaxially; hoods with entire apices
        5 Stems puberulent; plants 15-90 cm tall; leaves ascending to spreading; corollas greenish-cream colored on both surfaces; hoods with deeply 2-lobed apices
      4 Leaf blades flat to slightly conduplicate.
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
          6 Umbel 1, terminal; corona 5-7 mm in diameter; horns present, about as long as the hood; hoods ca. 2-4 mm long, surpassing the anther heads; [dry pinelands of the Coastal Plain]
(c) Ward, Scott G
          6 Umbels 1-4, terminal and from upper nodes; corona 2-3 mm in diameter; horns absent; hoods ca. 2 mm long, surpassed by the anther heads; [either wet pinelands of the Coastal Plain or dry glades or woodlands].
             7 Leaf blades narrowly linear (needlelike); stems 1-13 from ground level, 10-30 cm tall; umbels 3-13 flowered, pedunculate; corolla lobes cream to suffused pink, the lobes reflexed with widely spreading tips; [grasslands in c. OK westward]
             7 Leaf blades linear-lanceolate; stems typically 1-3 from ground level, 25-125 cm tall; umbels 10-100 flowered, sessile or pedunculate; corolla lobes green to whitish or greenish-cream and red-violet at tips, the lobes strongly reflexed with the tips lightly spreading or less commonly strongly spreading [widespread; habitats various].
               8 Pedicels with spreading hairs; umbels 2-10, each with up to 30-100 flowers; leaves minutely scabrous; [dry glades or woodlands, known from the Mountains of nw. GA, e. TN, w. WV westward]
               8 Pedicels with incurved hairs; umbels 1-6, each with 10-30 flowers; leaves glabrous or nearly so; [wet pinelands of the Coastal Plain]
(c) Bradley, Keith
(c) Ward, Scott G
(c) Davis, Scott Allen - CC-BY
1 Leaves opposite; corolla white, whitish, or greenish, usually suffused with rose-purple (especially at the tips of the corolla lobes), or creamy yellow, purple, or orange-red.
(c) Ward, Scott G
                 9 Corolla lobes erect (vertical), creamy yellow to dull or greenish white, 7-10 mm long; leaves 2.5-4.5 cm long, puberulent beneath, sessile; plant 1-4 dm tall; [dryish pinelands of the Coastal Plain]
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
                 9 Corolla lobes reflexed to spreading, either orange-red, with at least some purple, or whitish or greenish, 3-7 mm long (except 8-11 mm long in the orange-red A. lanceolata); leaves (3-) 5-20 cm long, glabrous or glabrate beneath (rarely puberulent), sessile to petiolate; plant 1-15 dm tall; [collectively of various habitats].
                   10 Leaves with petioles 1-10 mm long; leaves 5-15 mm wide; plants 5-15 dm tall.
(c) Cressler, Alan M.
                     11 Petiole 4-10 mm long; corolla pink (rarely white), the lobes 3-5.5 mm long; hoods 1-2 mm long; horns longer than the hoods; [mostly of the Mountains and Piedmont]
(c) Ward, Scott G
                     11 Petiole 1-3 mm long; corolla orange-red, the lobes 8-11 mm long; hoods 5-6 mm long; horns slightly shorter than the hoods; [of the Coastal Plain]
                   10 Leaves sessile, subsessile (with petioles 0-1 mm long); leaves 1-7 mm wide; plants 1-7 dm tall.
(c) Ward, Scott G
(c) Sorrie, Bruce A. - CC-BY
                       12 Leaves 3-7 mm wide.
                          13 Umbel 1, terminal; corona 5-7 mm in diameter; horns present, about as long as the hood; hoods ca. 2-4 mm long, surpassing the anther heads; [dry pinelands]
                          13 Umbels 1-10, terminal and from upper nodes; corona 2-3 mm in diameter; horns absent; hoods ca. 2 mm long, surpassed by the anther heads; [either of wet pinelands of the Coastal Plain or dry glades or woodlands].
                            14 Pedicels with spreading hairs; umbels 2-10, each with up to 30-100 flowers; leaves minutely scabrous; [dry glades or woodlands, east to nw. GA, TN, and WV]
                            14 Pedicels with incurved hairs; umbels 1-6, each with 10-30 flowers; leaves glabrous or nearly so; [wet pinelands of the Coastal Plain]
(c) Davis, Scott Allen - CC-BY
                       12 Leaves 1-2.5 mm wide.
(c) Cressler, Alan M.
(c) Ward, Scott G
                              15 Pedicels ca. 2 cm long, arching, the flowers often nodding; horns present (somewhat longer than the hood); hoods with 2 erect, acuminate, marginal teeth on the inner side (adjoining the anther heads); corolla ashy-gray, pale violet, or pale rose; [se. NC (historically) and e. SC south to n. peninsular FL, west to s. MS]
                              15 Pedicels 0.6-1.5 cm long, erect to ascending, the flowers facing upwards (or with stiffly erect pedicels but some flowers in the umbel pointed downward in A. linearis); horns absent or present; hoods with or without marginal auricles; corolla white, pale pink, or green (and often suffused with purple); [TX to se. GA and s. AL south to s. FL].
                                16 Upper leaf surfaces puberulent with curved hairs; leaf margins ciliate; stems 1-4, stems often branched; inflorescences 7-20 flowered; corollas cream to brownish, occasionally suffused violet
                                16 Upper leaf surfaces glabrous; leaf margins glabrate to sparsely ciliate; stems 1-2, stems typically solitary (rarely branched near base); inflorescences 2-15 flowered; corollas white, whitish green, or green.
(c) Ward, Scott G
                                  17 Corolla white or pale pink; hoods shorter than the gynostegium; horns absent
(c) Griffith, Floyd A.
                                  17 Corolla green to cream, often suffused with purple; hoods longer than the gynostegium; horns present
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Key to Asclepias, Key D: milkweeds with milky sap, with petiolate, nonlinear leaves, in flower

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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]