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Key to Apocynaceae

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1 Plant erect or trailing (but not twining), herbaceous or woody.
  2 Plant a woody shrub, subshrub, or trailing woody vine.
    3 Leaves alternate.
      4 Fruit follicles; [waif]
      4 Fruit drupes; [native and non-native]
        5 Leaves lanceolate; corolla white, salverform, < 1 cm long; fruit white; [rare native, s. FL]
        5 Leaves linear; corolla yellow, funnelform, ca. 5 cm long; fruit green to brown; [non-native, s. TX and FL peninsula]
    3 Leaves opposite or whorled.
          6 Plants armed, the stems with stout, bifurcated spines
          6 Plants unarmed, the stems without spines.
             7 Plant rhizomatous, suffrutescent, < 4 dm tall; leaves narrowly to broadly ovate; flowers blue, lavender, or white
             7 Plant erect, > 4 dm tall; leaves either lanceolate or elliptic (or oblanceolate in Allamanda cathartica); flowers yellow, white, pink, or red.
               8 Flowers white, pink, or red; shrub 10-40 dm tall, much branched from the base; [commonly cultivated in our area (and sometimes persistent), particularly near the coast; NC s. to FL, w. to TX]
               8 Flowers yellow; plants erect subshrubs 4-12 dm tall (Angadenia berteroi) or trailing to erect woody vines 0-20 m tall (Allamanda cathartica); [FL].
image of plant
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                 9 Leaves oblanceolate, 15-40 mm wide, mostly in whorls of 3-4; plants larger trailing or erect woody vines; follicles rounded and spiny; [non-native of disturbed habitats, c. and s. FL]
                 9 Leaves narrowly elliptic to oblong, 2.5-10 mm wide, leaves opposite; plants smaller subshrubs; follicles smooth; [native of pine rocklands and marl prairies, s. FL]
  2 Plant an herb or trailing herbaceous vine.
                   10 Flowers with conspicuous or less conspicuous corona; follicles not paired; seeds with coma present.
                     11 Plant either an erect herb or a decumbent herb with stiff, thick stems (> 4 mm in diameter); leaves various, but not both petiolate and heart-shaped
                     11 Plant a trailing herbaceous vine with weak, thin stems (<2 mm in diameter); leaves petiolate and heart-shaped, 2-4 cm long
                   10 Flowers lacking corona; follicles paired (occasionally single by abortion); seeds with coma absent (Catharanthus, Amsonia) or present (Apocynum).
                       12 Leaves alternate (rarely a few on a plant subopposite)
                       12 Leaves opposite.
                          13 Flower < 8 mm across; paired follicles pendent, 10-22 cm long; seeds with coma; mature plants normally > 7 dm tall
                          13 Flower > 20 mm across; paired follicles erect, 1.5-2.5 cm long; seeds lacking coma; mature plants 2-6 dm tall
1 Plant twining, herbaceous or woody.
                            14 Leaves conspicuously cordate at base (or subcordate to truncate in Vinceotoxicum), ovate to broadly lanceolate, ca. 1-4× as long as wide.
                              15 Plants in flower.
                                16 Latex clear
                                  17 Flowers white-colored; leaf bases deeply cordate or sagittate
                                  17 Flowers maroon-colored; leaf bases usually truncate or rounded (occasionally subcordate)
                                16 Latex white
                                    18 Stems glabrous to puberulent (the hairs sometimes curved), but lacking glandular-capitate hairs; petals white; gynostegial corona > ¾ as long as the corolla lobes.
                                       19 Corolla lobes green with white margins, conspicuously bicolored; MORE
                                       19 Corolla lobes uniformly whitish or cream colored, unicolored; MORE
                                    18 Stem pubescence a mix of eglandular and glandular-capitate hairs; petals purple-black, brown, yellow, yellow-green, cream, or maroon (white in Matelea baldwyniana); gynostegial corona < ½ as long as the corolla lobes.
                                         20 Corolla lobes glabrous on the outer surface; dorsal anther appendages laminar; carpels smooth and angled
                                         20 Corolla lobes glandular-puberulent or puberulent on the outer surface; dorsal anther appendages absent; carpels muricate (Matelea)
                              15 Plants in fruit.
                                           21 Latex clear.
                                             22 Corona a fleshy, lobed cup
                                             22 Corona nearly as long as to longer than the corolla lobes
                                           21 Latex white.
                                               23 Follicles muricate (appearing studded)
                                               23 Follicles smooth, with or without apparent angles but not studded.
                                                 24 Stem pubescence a mix of eglandular and glandular-capitate hairs
                                                 24 Stems glabrous to puberulent (the hairs sometimes curved), but lacking glandular-capitate hairs.
                                                    25 Stems with nodes conspicuously pubescent, often with curved trichomes throughout; MORE
                                                    25 Stems puberulent in a single line or glabrate; MORE
                            14 Leaves not cordate at base (cuneate, rounded, or truncate; occasionally subcordate but this not predominant); leaves ovate, lanceolate, or linear, ca. 1.5-10x as long as wide.
                                                      26 Leaves linear, the margins parallel.
                                                        27 Leaves petiolate; calyx lobes deltoid, obtuse, ca. 1 mm long; leaves petiolate, not reflexed, often caducous; follicle 1-3 mm in diameter; [of se. SC and southwards]
                                                        27 Leaves sessile; calyx lobes lanceolate, acute, (1.3-) 1.5-2.5 mm long; leaves sessile, reflexed, persistent; follicle 6-7 mm in diameter; [of ne. NC and southwards]
                                                      26 Leaves not linear, instead ovate or lanceolate (rarely deltoid/rhomboid shaped).
                                                          28 Flowers brownish-purple or maroon-colored.
                                                            29 Stems herbaceous; corollas maroon-colored throughout, without green corolla margins; [widespread non-natives, ne. US]
                                                            29 Stems woody; margins of corolla lobes often with green coloration; [waif or rarely garden escapes]
                                                          28 Flowers primarily white, whitish-green, creamy yellow, pure yellow, or light pink.
                                                              30 Flowers with a gynostegial corona (crown-like structure), greenish-white or pale pink colored
                                                                 31 Corolla lobes 1.5-3.5 mm long; leaves linear to ovate (but never hastate); [native of rocklands, woodlands, hammocks, pastures; TX and FL]
                                                                 31 Corolla lobes 7-13 mm long; leaves ovate, deltate, or hastate; [non-native of disturbed habitats; FL]
                                                              30 Flowers lacking a corona, white to creamy yellow or pure yellow colored.
                                                                   32 Corolla lobes 3-4 mm long, acute, reflexed, pale yellow; leaves subcoriaceous; [native, common]
                                                                   32 Corolla lobes 8-18 mm long, rounded, spreading, white; leaves coriaceous; [native or non-native].
                                                                     33 Corolla salverform, long and tubular (viewing flower from the side), the lobes 11-18 mm long; [native, s. FL]
                                                                     33 Corolla campanulate (above short cylindric base, view flower from side), the lobes 8-12 mm long; [non-native]

Key H: woody plants with whorled leaves

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1 Leaves tiny, bract-like, triangular, 6-14 (-17) per node
1 Leaves either needle-like, scale-like, or flattened and large, (2-) 3-4 (-6) per node.
  2 Leaves needle-like or scale-like, terete, angled, or flat in ×-section, < 2 cm long; leaves (2-) 3-4 (-6) per node
  2 Leaves flat, > 3 cm long; leaves (2-) 3 per node; [Eudicots].
    3 Plant a subshrub, < 3 dm tall, with < 10 leaves per stem.
      4 Leaves entire, broadly elliptic; flowers numerous, in a hemispherical head, subtended by 4 large white bracts
      4 Leaves serrate, narrowly ovate or narrowly obovate; flowers (1-) 2-8 in a long-peduncled umbel or corymb, not subtended by bracts
    3 Plant a shrub or tree, > 3 dm tall, with many > 10 leaves per stem.
        5 Leaves toothed, and most leaves also lobed
        5 Leaves entire, not lobed.
          6 Leaves cordate at base; leaves about as long as wide; medium to large tree.
             7 Flowers white to yellow; capsules linear, >10× as long as wide; leaf undersurface with curly simple hairs; nectar glands present in the main vein axils on the undersurface of the leaf (visible from the underside or the upperside in fresh leaves and herbarium specimens as a triangle 1-4 mm on a side)
             7 Flowers lavender; capsules ellipsoid, < 2× as long as wide; leaf undersurface with branched (dendritic or stellate) hairs; nectar glands absent
          6 Leaves cuneate to rounded at base; leaves > 1.5× as long as wide; shrub to small tree.
               8 Leaves rounded at the tip
               8 Leaves acute to acuminate at the tip.
                 9 Leaves lanceolate or oblong-elliptic (> 2.5× as long as wide), the secondary venation not prominent; inflorescences axillary or terminal; flowers pink or white.
                   10 Inflorescences axillary; flowers pink; leaves thin and herbaceous; [native plants of wetlands]
                   10 Inflorescences terminal or axillary; flowers pink or white; leaves thick and leathery; [exotics of uplands or wetlands, persistent or weakly naturalized]
                     11 Fruit berry-like with 2-locular ovaries; flowers white-colored, smaller; inflorescence axillary or pseudo-terminal; leaves opposite to whorled
                     11 Fruit follicles; flowers variously colored, showy and salverform; inflorescence terminal; leaves alternate to whorled (pseudo-whorled)
                 9 Leaves ovate (< 2× as long as wide), the secondary venation prominent and arching-parallel; inflorescences terminal; flowers white, greenish-yellow, red, or orange.
                       12 Flowers in a spherical or hemispherical head; corollas white or greenish-yellow
                       12 Flowers in a monochasial helicoid cyme; corollas red to orange