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Key to Rhododendron

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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 urceolate, the corolla lobes ca. 1 mm long; stamens 8; capsule 4-7 mm long, 4 (-5) locular; leaf mucro extremely prominent; midrib on lower leaf surface with a series of fascicles of glandular trichomes; [subgenus Azaleastrum, section Sciadorhodion]
............ ..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 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

Key to Ericaceae, Key D: Evergreen ericaeous shrubs (either tall or obviously clonal) and trees

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1 Leaves linear, needle-like, either appearing whorled (at least in part, sometimes also with nodes appearing opposite or alternate) or opposite (Calluna).
..2 Leaves opposite, sessile and clasping; [exotic, rarely naturalized]
..2 Leaves whorled (at least in part), petiolate (sometimes short-petiolate); [either native or exotic and rarely naturalized].
....3 Leaves densely puberulent and ciliate with gland-tipped hairs; leaves 1.5-5 mm long; [exotic, rarely naturalized]
....3 Leaves glabrous; leaves 2.5-15 mm long; [native].
......4 Plants erect shrubs 5-25 dm tall; leaves 5-15 mm long; drupes red, 1.5-2 mm in diameter; [of xeric or scrubby sites, SC southward]
......4 Plants subshrubs, erect or sprawling, stems 1.5-10 dm tall (or long in Empetrum); drupes gray or dark black, 1-1.5 mm (Corema) or 5-10 mm (Empetrum) in diameter; [dry sites, NJ northward].
........5 Stems prostrate, trailing; leaves 2.5-7 mm long, densely overlapping along stems; fruit a fleshy black drupe, 5-10 mm in diameter; flowers arranged on pedicels from leaf axils
........5 Stems upright, not trailing; leaves 3-6 mm long; fruit a dry gray drupe, 1-1.5 mm in diameter; flowers arranged in small terminal clusters
1 Leaves broader, alternate (or whorled or opposite in some Kalmia).
..........6 Leaves (all of them) < 2 cm long.
............ 7 [Either of the Mountains, the Piedmont, or the Coastal Plain of ne. SC and se. NC and northwards].
............ ..8 Leaves alternate, glabrous, finely serrulate
............ ..8 Leaves alternate or opposite, stipitate-glandular or glabrous, entire, or with a few obscure teeth
............ 7 [Of the Coastal Plain, from se. SC southward].
............ ....9 Twigs densely hispid; leaves hispid on both surfaces
............ ....9 Twigs glabrous to puberulent; leaves glabrous or with scattered inconspicuous hairs.
............ ......10 Plant glaucous and bluish-green throughout; leaf undersurface lacking scattered glandular hairs; [of s. GA south to s. peninsular FL, west to e. TX]
............ ......10 Plant dark green throughout, generally exceeding 20 mm in length; leaf undersurface with scattered glandular hairs, these sometimes very few by late in the season (best seen in the field by folding a leaf, holding the fold up to the light, and using a 10× lens); [of se. SC southward to n. FL, west to s. AL]
..........6 Leaves (at least the larger) > 3 cm long.
............ ........11 Leaves toothed, at least toward the tip of the leaf (note that fine serrations or crenations can be obscured by revolute margins).
............ ..........12 Leaves elliptic to oblanceolate, widest near or above the middle, obtuse, acute, or short-acuminate, 1.5-7 cm long, 0.5-2.5 cm wide; leaf serrations fine and obscure; leaf surfaces with small stipitate glands (Pieris) or lepidote with scales (Chamaedaphne).
............ ............ 13 Leaves lepidote with scales; leaves oblanceolate, widest above the middle
............ ............ 13 Leaves with small stipitate glands, otherwise appearing glabrous; leaves elliptic, widest near the middle.
............ ............ ..14 Inflorescence a many-flowered panicle of racemes, borne terminally; seeds 2.5-3 mm long; [of slopes and ridges of the Mountains and upper Piedmont]
............ ............ ..14 Inflorescence a 3-9 flowered raceme, borne in the axils of upper leaves; seeds ca. 1 mm long; [of wetlands of the Coastal Plain, often associated with Taxodium ascendens]
............ ..........12 Leaves lanceolate or ovate, widest below the middle, short-acuminate to acuminate, 4-15 cm long, 1-5 cm wide; leaf serrations generally obvious (at least toward the acuminate leaf tip); leaf surfaces glabrous, or with non-stipitate hairs on the lower surface.
............ ............ ....15 Pith transversely diaphragmed; [pedicels slender, 7-10 mm long]; [filaments strongly curved just below the anthers]
............ ............ ....15 Pith solid; [pedicels stout, 2-6 mm long]; [filaments straight].
............ ............ ......16 Leaves obtuse or acute to short-acuminate; staminal filaments almost always with at least a few unicellular hairs; calyx lobes ovate-triangular to ovate or widely so, 1.2-2.3 mm wide; racemes 0.9-5.5 cm long, with 8-44 flowers; sepals ovate, with an obtuse or rounded apex; longest petioles 2-10 (-11) mm long; [of the Coastal Plain and lower Piedmont]
............ ............ ......16 Leaves long-acuminate, petiole (5-) 6-16 mm long; staminal filaments merely papillose; calyx lobes ovate or ovate-triangular to oblong-triangular, 0.7-1.6 mm wide; racemes 2-10 cm long, with 17-80 flowers; longest petioles 8-15 mm long; [of the Mountains and upper Piedmont]
............ ........11 Leaves entire.
............ ............ ........17 Leaves densely pubescent beneath, either whitened beneath by a dense mat of fine white hairs or brown tomentose with coarse and twisted hairs; leaves strongly revolute
............ ............ ..........18 Leaves linear; leaf undersurface whitened beneath by a dense mat of fine white hairs
............ ............ ..........18 Leaves lanceolate or narrowly elliptic; leaf undersurface brown tomentose with coarse and twisted hairs
............ ............ ........17 Leaves glabrous, glabrescent, or lepidote with scales, appearing green or brownish; leaves planar, slightly revolute or strongly revolute.
............ ............ ............ 19 Leaves densely lepidote on the under surface with brown scales.
............ ............ ............ ..20 Leaves planar, not revolute; petioles 7-20 mm long; twigs more-or-less terete in cross-section; [of the Mountains, Piedmont, and upper Coastal Plain].
............ ............ ............ ....21 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 occurring at higher elevations and more northern latitudes; 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; [of mountain ridges, heath balds, and rocky summits, mostly either away from the Blue Ridge Escarpment or north of the Asheville Basin]
............ ............ ............ ....21 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; seeds usually > 1.0 mm long, usually > 3× as long as wide, ornamented at one or both ends; calyx lobes ovate; [of the Coastal Plain, Piedmont, and Mountains, in the Mountains mostly of the Blue Ridge Escarpment of sw. NC and nw. SC, ranging in elevation up to the higher granitic domes in Macon and Jackson counties, NC].
............ ............ ............ ......22 Leaf apices mostly obtuse to rounded; petioles 2-6 (-7) mm long; branches erect and rigid; seeds moderately to elaborately ornamented with flared protrusions at both ends; [of n. FL]
............ ............ ............ ......22 Leaf apices mostly acute to acuminate; petioles (5-) 6-20 mm long; branches spreading, not notably erect and rigid; seeds somewhat ornamented at one end; [of c. GA northward]
............ ............ ............ ..20 Leaves slightly to strongly revolute (or nearly planar in Lyonia fruticosa); petioles 1-7 mm long; twigs angled in cross-section; [of the lower Coastal Plain, from se. SC southward].
............ ............ ............ ........23 Ultimate branches not rigidly ascending, flowers nearly always restricted to branches of the previous year, the leaves not conspicuously reduced toward the branch tips; leaves with distal margin usually revolute, sometimes strongly so; major veins usually depressed; lower leaf surface with some scales often large and with irregular margins, others smaller and more nearly entire, at least the smaller scales more-or-less persistent; [shrub or small tree to 6 (-10) m tall]
............ ............ ............ ........23 Ultimate branches rigidly ascending, flowers frequent on branches of the current year (though also on older growth), the leaves conspicuously reduced toward the branch tips; leaves with distal margin at most slightly revolute; major veins not depressed; lower leaf surface with scales usually all large and with irregular margins, the scales often deciduous; [shrub to 1.5 (-3) m tall]
............ ............ ............ 19 Leaves not lepidote beneath (Lyonia lucida with scattered minute scales on young leaves).
............ ............ ............ ..........24 Leaves whorled or rarely opposite.
............ ............ ............ ............ 25 Calyx lobes glandular-canescent and with marginal stipitate glands; leaves glabrous beneath; bracts and bracteoles densely glandular; stomates 18 μ long and 13 μ wide, 15-24 per 0.2 square millimeter; shrub to 1 (-1.2) m tall; [of ne. NC northward]
............ ............ ............ ............ 25 Calyx lobes canescent but lacking glands; leaves short puberulent beneath; bracts and bracteoles nearly glandless; stomates 13 μ long and 9 μ wide, 35-51 per 0.2 square millimeter; shrub to 2 m tall (though often much shorter); [of se. and sw. VA southward]
............ ............ ............ ............ ..26 Leaf blades (8-) 10-30 cm long, 3-9 cm wide, rounded to obtuse at the tip.
............ ............ ............ ............ ....27 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
............ ............ ............ ............ ....27 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
............ ............ ............ ............ ..26 Leaf blades 2-10 (-12) cm long, 1-5 cm wide, acute, short-acuminate (or obtuse or rounded in Cyrilla) at the tip.
............ ............ ............ ............ ......28 Leaf with a prominent vein running the length of the margin, about 1 mm in; [shrub to 4 m tall]
............ ............ ............ ............ ......28 Leaf venation not as above; [shrub to small tree] {Kalmia latifolia, Cyrilla, Cliftonia, Bejaria}
............ ............ ............ ............ ........29 Fruit a locular, dehiscent capsule, never winged; seeds usually present in fruit, very numerous, often 100-300 per fruit; [dry sites].
............ ............ ............ ............ ..........30 Stems hispid-tomentose (the hairs usually brown or rusty-colored); plants densely glandular, particularly along stems and flowers; capsules 7-locular; [endemic to xeric habitats in southeastern coastal plain, se SC to s. FL]
............ ............ ............ ............ ..........30 Stems glabrescent, viscid or stipitate-glandular (never hispid-tomentose); capsules 5-locular; flowers connate and strongly radially symmetric, campanulate, petals connate, [Creek and forest bluffs in n. FL and FL panhandle, otherwise primarily in drier piedmont and mountain sites n. to Ontario]
............ ............ ............ ............ ........29 Fruit an indehiscent drupe (winged or not); seeds usually absent from fruit, sometimes 1-5; [wet sites, except for Cyrilla arida].
............ ............ ............ ............ ............ 31 Racemes terminal and axillary; fruit 5-7 mm long, 2-5 winged
............ ............ ............ ............ ............ 31 Racemes only lateral, clustered together at the summit of previous year's growth and radiating outward or reflexed; fruit 2-2.5 mm long, not winged
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