1 Plant an herb, subshrub, or sprawling shrub, not clonal by underground rhizomes (except Gaultheria procumbens and Epigaea repens), rarely > 3 dm tall; plants mycotrophic or hemi-mycotrophic (except Epigaea, Gaultheria, and Arctostaphylos).

  2 Plants without chlorophyll (fully mycotrophic); stems fleshy; leaves represented by bract-like scales, white or variously colored, but not green; pollen grains single; [subfamily Monotropoideae; tribe Monotropeae].

    3 Petals united; fruit nodding, a berry; flower and fruit several per stem

    3 Petals separate; fruit erect, a capsule; flower and fruit 1-several per stem.

      4 Flowers few to many, racemose; stem pubescent, at least in the inflorescence; plant yellow, orange, or red when fresh, aging or drying dark brown

      4 Flower solitary; stem glabrous; plant white (rarely pink) when fresh, aging or drying black

  2 Plants with chlorophyll (hemi-mycotrophic or autotrophic); stems woody; leaves present and well-developed, green; pollen grains in tetrads (single in Orthilia).

        5 Herb with a rosette of ascending basal leaves; flowers scapose; [subfamily Monotropoideae; tribe Pyroleae].

          6 Style and filaments straight; filaments straight, the anthers closely surrounding the style; inflorescence distinctly secund (1-sided)

          6 Style and filaments strongly declined; filaments curved, the anthers not closely surrounding the style; inflorescence slightly or not at all secund (1-sided)

        5 Subshrub or sprawling shrub with cauline leaves; flowers axillary (except scapose in Chimaphila).

             7 Plant erect, the leaves clustered near the apex of the single stem.

               8 Leaves lanceolate or oblanceolate, normally 2-4× as long as wide (sometimes proportionately less narrow in stunted individuals; fruit a capsule, borne 1-several on an erect scape above the leaves [subfamily Monotropoideae; tribe Pyroleae]

               8 Leaves obovate, 1-2× as long as wide; fruit a red berry, borne on nodding axillary pedicels beneath the leaves; [subfamily Vaccinioideae; tribe Gaultherieae]

             7 Plant creeping or sprawling, leaves scattered along the stems.

                 9 Flowers solitary and axillary; fruit a white berry; [subfamily Vaccinioideae; tribe Gaultherieae]

                 9 Flowers in axillary or terminal spikes or racemes; fruit a fleshy loculicidal capsule or red drupe.

                   10 Leaves glabrous, 1-3 cm long, tapered to the base; corolla urceolate; calyx not subtended by large bracts; [subfamily Arbutoideae]

                   10 Leaves pilose (glabrate in age), 2-10 cm long, rounded or subcordate at the base; corolla salverform, the lobes spreading; calyx subtended by 2 large bracts; [subfamily Ericoideae; tribe Phyllodoceae]

1 Plant either a shrub or tree (> 3 dm tall), or a shrub 1-3 dm tall (rarely a woody needle-leaved subshrub 0.5-1 m and definitely and obviously clonal by underground rhizomes; plants not mycotrophic or hemi-mycotrophic.

                     11 Leaves ca. 1 mm wide, 3-12 mm long, appearing opposite, alternate, or whorled (the internodes very short, thus the leaves generally appearing whorled); petals absent; fruit a subglobose, 2-stoned drupe, 1-3 mm in diameter; branches often appearing in whorls of 3-7; [subfamily Ericoideae; tribe Empetreae]

                       12 Leaves 5-15 mm long; shrubs 5-25 dm tall; drupes yellow or reddish, 1.5-3 mm in diameter; [of SC southward]

                       12 Leaves 3-6 mm long; shrubs 1.5-6 dm tall; drupes gray, 1-1.5 mm in diameter; [of NJ northward]

                     11 Leaves either > 2 mm wide or < 5 mm long, mostly alternate or whorled; petals present; fruit not as above, mostly either a capsule or 10- or many-seeded berry; branches appearing alternate or whorled; [subfamily Vaccinioideae; tribe Vaccinieae].

                          13 Ovary inferior; fruit indehiscent, a fleshy berry; [blueberries and huckleberries].

                            14 Ovary 10 locular; seeds 10; leaves glandular-punctate, at least on the lower surface (except G. brachycera)

                            14 Ovary 4-5 locular; seeds numerous; leaves not glandular-punctate

                          13 Ovary superior; fruit dehiscent, a dry capsule; [other heaths].

                              15 Petals separate; fruit 2-7-locular; either a shrub to 1 m tall with ovate to oblong, evergreen leaves, 0.6-1.2 cm long, or a shrub to small tree 2-6 (-9) m tall with elliptic, deciduous leaves, 4-12 cm long, or a shrub 1-2.5 m tall, with elliptic to ovate, evergreen leaves 2-4 cm long; [subfamily Ericoideae; tribe Phyllodoceae]. {add Rhododendron groenlandicum}

                                16 Fruit 2-3 (5)-locular; shrub to 1 m tall; leaves, 0.4-1.2 cm long; petals 2-4 mm long

                                16 Fruit 4-7-locular; shrub to small tree 1-6 (-9) m tall; leaves 2-12 cm long; petals 12-30 mm long.

                                  17 Fruit 7-locular; leaves evergreen 2-4 cm long; petals 20-30 mm long; shrub 1-2.5 m tall

                                  17 Fruit 4-5-locular; leaves deciduous, 4-12 cm long; petals 12-14 mm long; shrub to small tree 2-6 (-9) m tall

                              15 Petals fused for part or all their lengths; fruit (4-) 5-locular; shrub or tree with leaves of various shape, evergreen or deciduous, these either < 6 mm long, linear and whorled, or > 12 mm long.

                                    18 Leaves opposite or whorled, < 5 mm long, linear; [subfamily Ericoideae, tribe Ericeae]

                                       19 Leaves opposite, sessile, clasping at the base

                                       19 Leaves whorled (in 4s), petiolate

                                    18 Leaves alternate or whorled, > 20 mm long.

                                         20 Flowers 5-merous; fruits 5-locular; leaves not as above.

                                           21 Leaves coriaceous, evergreen, shiny and dark green above.

                                             22 Leaves sharply and distinctly serrate.

                                               23 Pedicels slender, 7-10 mm long; filaments strongly curved just below the anthers; pith transversely diaphragmed; [subfamily Vaccinioideae; tribe Lyonieae]

                                               23 Pedicels stout, 2-6 mm long; filaments straight; pith solid; [subfamily Vaccinioideae; tribe Gaultherieae]

                                             22 Leaves entire, or obscurely and finely crenulate-serrulate.

                                                 24 Capsules elongate, > 2× as long as broad, 8-18 mm long; [subfamily Ericoideae; tribe Rhodoreae]

                                                 24 Capsules ovoid to globose or subglobose, about as long as broad, 5-8 mm long.

                                                    25 Leaves with a prominent vein running parallel to (and about 1 mm in from) the margin; [subfamily Vaccinioideae; tribe Lyonieae]

                                                    25 Leaves without a prominent marginal vein.

                                                      26 Corolla saucer-shaped, 10-30 mm across; leaves entire; [subfamily Ericoideae; tribe Phyllodoceae]

                                                      26 Corolla narrowly urceolate, 4-6 mm across; leaves finely crenulate-serrulate; [subfamily Vaccinioideae; tribe Lyonieae]

                                                        27 Flower stalks with 2 opposite or subopposite subulate bractlets a little below the calyx; leaves glabrous below or short-pubescent on the midvein

                                                        27 Flower stalks with 2 opposite or subopposite triangular bractlets near the base of the pedicel; leaf lower surface punctate with stalked red glands

                                           21 Leaves membranaceous or subcoriaceous, deciduous or evergreen, if subcoriaceous and evergreen, then not shiny and dark green above.

                                                          28 Capsules elongate, > 2× as long as broad, 7-23 mm long; [subfamily Ericoideae; tribe Rhodoreae]

                                                          28 Capsules ovoid to globose or subglobose, about as long as broad, or broader than long, 2-7 mm long.

                                                            29 Leaves (at least the larger) > 2.5 cm wide.

                                                              30 Pedicels with 2 bracteoles.

                                                                 31 Capsule broader than long; shrub; bracteoles just below the calyx; [subfamily Vaccinioideae; tribe Gaultherieae]

                                                                 31 Capsule longer than broad; tree; bracteoles generally near the middle of the pedicel; [subfamily Vaccinioideae; tribe Oxydendreae]

                                                              30 Pedicels without bracteoles.

                                                                   32 Leaves entire to minutely serrulate; capsule sutures pale and thickened; [subfamily Vaccinioideae; tribe Lyonieae]

                                                                   32 Leaves crenate; capsule sutures not thickened and pale; [subfamily Vaccinioideae; tribe Andromedeae]

                                                            29 Leaves < 2.5 cm wide.

                                                                     33 Leaves linear to narrowly lanceolate, 8× or more as long as wide. strongly revolute, strongly whitened beneath; [subfamily Vaccinioideae; tribe Andromedeae]

                                                                     33 Leaves broader, not revolute or slightly so, not strongly whitened below.

                                                                       34 Leaves whorled or alternate; corolla saucer-shaped, 10-20 mm across; [subfamily Ericoideae; tribe Phyllodoceae]

                                                                       34 Leaves alternate; corolla narrowly urceolate, 2-8 mm across.

                                                                         35 Pedicels with 2 bracteoles near the summit; [subfamily Vaccinioideae; tribe Gaultherieae]

                                                                         35 Pedicels with 2 bracteoles near the base; [subfamily Vaccinioideae; tribe Lyonieae]

1 Leaves evergreen, coriaceous, entire; [rhododendrons and Labrador-tea].

  2 Leaves densely hairy beneath; petals separate

  2 Leaves either glabrous beneath or punctate with brown scales; petals fused.

    3 Lower surface of leaves not punctate with brown scales; larger leaves 10-30 cm long; [subgenus Hymenanthes, section Ponticum, subsection Pontica].

      4 Leaves rounded at base (rarely broadly cuneate or slightly cordate), obtuse at apex; leaf generally 1.5-2.5× as long as wide; corolla usually deep pink to purple; sepals 0.5-1 mm long

      4 Leaves cuneate at base, acute at apex; leaf generally 3-5× as long as wide; corolla usually white to pale pink; sepals 4-6 mm long

    3 Lower surface of leaves punctate with brown scales; larger leaves 6-12 cm long; [subgenus Rhododendron, section Rhododendron, subsection Caroliniana].

        5 Narrow part of the corolla tube ca. 0-2 mm long; peak flowering simultaneous with peak flowering of Kalmia latifolia; [restricted to the Great Smoky Mountains, TN and NC]

        5 Narrow part of the corolla tube > 4 mm long; main flowering before to simultaneous with Kalmia latifolia; [FL, AL, GA, TN, SC, and NC].

          6 Leaf apices mostly obtuse to rounded; leaves mostly 4.5-6.0 cm long, 1.7-2.4 cm wide, in the sun clearly revolute; petioles 2-6 (-7) mm long; branches erect and rigid; seeds moderately to elaborately ornamented with flared protrusions at both ends; [n. FL]

          6 Leaf apices mostly acute to acuminate; leaves mostly 6-11 cm long, 2.0-4.0 cm wide, flat or only slightly revolute; petioles (5-) 6-20 mm long; branches spreading, not notably erect and rigid; seeds somewhat ornamented at one end; [c. GA northward].

             7 Corolla mostly 15-20 mm long, the corolla tube (9-13 mm long) shorter than to as long as the corolla lobes (12-18 mm long); plant flowering early relative to R. minus, despite often occurring at higher elevations and more northern latitudes, the main flowering in early spring, long before Kalmia latifolia; leaf growth starting with or after flowering; seeds ovoid, < 1.0 mm long, < 2.5× as long as wide (reminiscent of tiny watermelon seeds), coarsely textured, unornamented at the ends; calyx lobes deltoid; [mountain ridges, heath balds, and rocky summits, mostly either away from the Blue Ridge Escarpment or north of the Asheville Basin]

             7 Corolla mostly 25-37 mm long, the corolla tube (13-22 mm long) longer than the corolla lobes (8-12 mm long); plant flowering late relative to R. carolinianum, the main flowering in late spring, together with Kalmia latifolia; leaf growth before flowering (and in southern parts of the range also after flowering); seeds usually > 1.0 mm long, usually > 3× as long as wide, ornamented at one or both ends; calyx lobes ovate; [Coastal Plain, Piedmont, and Mountains, in the Mountains mostly of the Blue Ridge Escarpment of sw. NC and nw. SC, ranging up to the higher granitic domes in Macon and Jackson counties, NC].

1 Leaves deciduous, membranaceous, ciliate or serrulate; [azaleas, minniebush, and rhodora].

               8 Corolla tubular at the base, with well-developed flaring corolla lobes > 10 mm long (at least the lower); stamens either 5-7 or 10; capsule 7-25 mm long, 5-locular; leaf mucro not prominent; midrib on lower leaf surface variously pubescent, but not with a series of fascicles of glandular trichomes.

                 9 Corolla tube 2-5 mm long or absent, much shorter than the corolla lobes; stamens (5-) 7 or 10; capsule ellipsoid-ovoid, 7-14 mm long; [subgenus Azaleastrum, section Sciadorhodion].

                   10 Corolla tube absent; stamens 10; leaves elliptic to obovate, < 3 cm wide, acute to rounded at the apex, the margin revolute; [PA and NJ northwards]

                   10 Corolla tube 2-5 mm long, much shorter than the corolla lobes; stamens (5-) 7; leaves elliptic, often broadly so (commonly 3-6 cm wide), acuminate, often with purplish coloration, the margin plane; [endemic in the s. Blue Ridge]

                 9 Corolla tube 13-25 mm long, equal to or longer than the corolla lobes; stamens 5; capsule cylindroid-ellipsoid, 10-25 mm long; [subgenus Hymenanthes, section Pentanthera].

                     11 Outer (abaxial) surface of the vegetative bud scales densely pubescent; flowers appearing before or with the leaves (at least some of the leaves still folded or the vegetative bud scales still present) (except R. viscosum).

                       12 Capsule cylindroid, (3-) 4-5× as long as broad.

                          13 Corolla yellow-orange to orange-red; upper corolla lobe with a contrasting blotch; [s. GA west to se. MS]

                          13 Corolla white to pink; upper corolla lobe uniform in color (lacking a contrasting blotch); [collectively widespread in our area].

                            14 Corolla tube narrow and somewhat abruptly expanding into the lobes, the lobes distinctly shorter than the tube; pedicels usually eglandular (occasionally glandular), (4-) 5-10 (-13) mm long; leaves inconspicuously ciliate, the cilia appressed to the leaf margin; capsule densely covered with nonglandular hairs; flowering Mar-May; [widely distributed from s. NC and n. TN southward]

                            14 Corolla tube broader, gradually expanding into the lobes, the lobes about as long as or longer than the tube; pedicels usually glandular, (7-) 10-16 (-26) mm long; leaves conspicuously ciliate, the cilia diverging from the leaf margin; capsule glabrous or sparsely pubescent, the hairs at least partly gland-tipped; flowering May-Jun; [Mountains and upper Piedmont from n. NC (and rarely ne. AL) northward]

                       12 Capsule ovoid, 2-3 (-4)× as long as broad (if capsules absent, try both leads).

                              15 Corolla yellow-orange to orange-red; upper corolla lobe with a contrasting blotch; hairs of the capsule not gland-tipped; [Piedmont and Coastal Plain of GA and w. SC]

                              15 Corolla white to pink; upper corolla lobe uniform in color (lacking a contrasting blotch); hairs of the capsule gland-tipped (at least in part; nonglandular hairs also present); [collectively widespread in our area].

                                16 Flowers appearing after the leaves have expanded (essentially all of the leaves unfolded, and the vegetative bud scales absent), typically May (Coastal Plain, low elevation, or south) to Aug (mountains, high elevation, or north)

                                  17 Shrubs to 7 m tall; floral winter bud scales 15-20, at least the inner acute and aristate; corolla tube glabrous within, > 2× as long as the lobes; [primarily Coastal Plain]

                                  17 Shrubs 1-2 (-5) m tall; floral winter bud scales 8-12 (-15), rounded (-mucronate) apically; corolla tube pubescent within, < 2× as long as the lobes; [more widespread]

                                16 Flowers appearing before or with the leaves (at least some of the leaves still folded or the vegetative bud scales still present), typically Apr-May (unless stimulated by fire or weather).

                                    18 Leaf blade (3.2-) 3.4-4.7 (-5.2) cm long, (0.8-) 1.1-1.9 (-2.0) cm wide; plant typically strongly rhizomatous; [Coastal Plain from s. NJ south to sc. GA]

                                    18 Leaf blade (3.9-) 5.0-7.3 (-8.7) cm long, (1.2-) 1.8-3.0 (-3.7) cm wide; plant typically nonrhizomatous; [Mountains and upper Piedmont]

                     11 Outer (abaxial) surface of the vegetative bud scales glabrous or sparsely pubescent; flowers appearing before, with, or after the leaves.

                                       19 Capsule cylindric, (3-) 4-5 × as long as broad; flowers appearing before or with the leaves (at least some of the leaves still folded or the vegetative bud scales still present).

                                         20 Corolla white, with a contrasting yellowish blotch on the upper lobe; [se. TN and w. GA westward]

                                         20 Corolla deep pink (rarely white or nearly so), lacking a contrasting blotch on the upper lobe; [widespread in our area]

                                       19 Capsule ovate, 2-3.5× as long as broad; flowers appearing before, with, or after the leaves.

                                           21 Corolla white to pink (sometimes with yellow blotches).

                                             22 Sepals 1.5-5 mm long; [primarily Appalachian: ne. PA and se. KY south to sc. NC, w. SC, c. GA, and c. AL]

                                             22 Sepals 0.1-1 mm long; [collectively widespread].

                                               23 Leaves densely and softly pubescent beneath; [SC]

                                               23 Leaves glabrous beneath, except for strigose bristles along the midrib and major veins; [collectively widespread].

                                                 24 Shrubs to 7 m tall; floral winter bud scales 15-20, at least the inner acute and aristate; corolla tube glabrous within, > 2× as long as the lobes; [primarily Coastal Plain]

                                                 24 Shrubs 1-2 (-5) m tall; floral winter bud scales 8-12 (-15), rounded (-mucronate) apically; corolla tube pubescent within, < 2× as long as the lobes; [more widespread]

                                           21 Corolla predominantly yellow, orange, or orange-red.

                                                    25 Flowers appearing before or with the leaves.

                                                      26 Floral bud-scales with glandular margins, the outer surface glabrous; corolla tube glandular-pubescent on its outer surface; sepals 2.0-3.0 mm long

                                                      26 Floral bud-scales with ciliate margins, the outer surface glabrous to sparsely pubescent; corolla tube pubescent (not glandular or rarely very weakly so) on the outer surface; sepals 0.5-3.0 mm long

                                                    25 Flowers appearing after the leaves have expanded.

                                                        27 Twigs glabrous; [south of ec. AL and wc. GA]

                                                        27 Twigs pubescent with multicellular hairs; [e. KY and w. VA south to ec. TN, n. GA, and ne. AL; apparently disjunct in the Piedmont of SC]

                                                          28 Shrubs upright, not stoloniferous; pedicel usually glandular-pubescent; corolla tube relatively wide, usually glandular-pubescent, yellow to orange or red; flower bud scales yellow-green (rarely with a brownish tinge)

                                                          28 Shrubs slightly to strongly stoloniferous; pedicel rarely glandular-pubescent; corolla tube relatively narrow, usually not glandular-pubescent, deep orange to red; flower bud scales brownish or at least brown-margined