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Key to Rhododendron
Ericaceae
Rhododendron
https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=40320
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].
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].
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 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]
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]
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 (plants occasionally stoloniferous and low-growing) ; floral winter bud scales 8-12 (-15), rounded (-mucronate) apically; corolla tube pubescent within, < 2× as long as the lobes; [more widespread].
18 Winter buds silky pubescent, with fewer total scales (5-7 of these larger than the basal scales); branchlets and pedicels with spreading hairs; shrubs usually not exceeding 1.25 m in height; flowers appearing in mid-June to early July; capsule 0.8-1.5 cm long, finely villose and glandular-setose; [Mountains of NC, SC and GA]
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).
19 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]
19 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.
20 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).
22 Plants flowering late spring (early to mid May); flower color variable (white, pink, or yellow); leaves ovoid, the bases cuneate; plants 3-7 m tall; plants tetraploid; [Red Hills region of s. AL and w. GA]
23 Corolla white to pink (sometimes with yellow blotches).
24 Sepals 1.5-5 mm long; [primarily Appalachian: ne. PA and se. KY south to sc. NC, w. SC, c. GA, and c. AL]
24 Sepals 0.1-1 mm long; [collectively widespread].
26 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]
26 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]
23 Corolla predominantly yellow, orange, or orange-red.
29 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]
30 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)
30 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
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Key G6: trees with alternate, simple, unlobed, entire leaves
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https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=40720
3 Fruit a hesperidium; petiole flanged or winged for most of its length (except C. reticulata, which sometimes lacks wings entirely), constricted at the base of the blade (except linear in C. medica)
3 Fruit various (but not a hesperidium); petiole linear (sometimes swollen, but not flanged nor winged with leafy tissue).
6 Leaves (when fresh) strongly odorous, glandular-punctate (appearing as translucent dots), with strongly parallel venation; bark on medium-aged to mature trees papery and peeling; fruit a sub-globse capsule (the hypanthium somewhat woody)
7 Plants exuding milky sap (when punctured); fruit a berry, these large, subglobose and roughened on the exterior (Manilkara) or smaller and ellipsoid to ovoid in shape (Chrysophyllum); plants (leaves or elsewhere) with rufous, 2-branched hairs (strongly rufous in Chrysophyllum; if leaves strongly glaucous and glabrous, as in Manilkara jamiqui, then leaf apices clearly retuse)
10 Flowers solitary, terminal, large (> 5 cm in diameter); pistils many, carpels separate; petals many (typically > 8); leaves mostly > 10 cm long (at least some on a branch longer than 10 cm); fruit an aggregate of follicles, each dehiscing along 1 suture; stipule scar circumferential at each node, encircling the twig
10 Flowers axillary or terminal, arranged variously in racemes, panicles, umbels, cymes, fascicles, or sometimes solitary (if so, < 5 cm in diameter); pistil 1, with 1-8 fused carpels; petals 3-8 (apetalous in Conocarpus); leaves < 30 cm long; fruit either a drupe, berry, or capsule; stipule scars either absent or linear or triangular, not circumferentially encircling the twig.
11 Inflorescence terminal, the flowers arranged in a corymb, umbel, compound cyme, raceme, or panicle (Pittosporum and Mangifera, sometimes in Conocarpus); fruit either a capsule (dehiscing along 1 to 5 longitudinal sutures, elongate in CAPPARACEAE) or a 1-4-seeded drupe (Bourreria; Canella; Mangifera; Lumnitzera).
12 Flowers bearing petals; plants of various inland and coastal habitats
(c) Buckmire, Zoya - CC-BY
(c) Bradley, Keith
16 Fruit a smaller drupe, the drupe bearing 4 bony nutlets with abaxial ridges; flowers white, rotate and salverform (the corolla tube evident), arranged in terminal cymes, the corolla lobes usually orbicular (flattened or if slightly reflexed, then lacking colored glandular ridges on the upper surface)
16 Fruit a large 1-seeded-drupe, the mesocarp fleshy; flowers not salverform (the flowers lacking an evident floral tube), typically arranged in a terminal panicle, the corolla lobes usually reflexed and with yellow or pink glandular ridges adaxially (on the upper surface, thus evident when in flower)
17 Capsules pendulous and conspicuously elongate-cylindric, borne on a slender gynophore; seeds few-many, contrasting sharply with the bright red capsule interior; plants shrubs or small trees, or sometimes loosely scrambling over other plants; stamens usually much longer than the petals and conspicuously exerted from the flowers
18 Ovaries 2-carpellate; capsules dehiscing along one major adaxial suture, appearing berry-like before dehiscence, the seeds often surrounded by a glutinous material
19 Capsules ovoid to globose or subglobose, about as long as broad, 5-8 mm long; leaves 5-12 cm long, 2-3× as long as wide
19 Capsules elongate, > 2× as long as broad, 8-18 mm long; leaves 10-30 cm long, 3-5× as long as wide
11 Inflorescence axillary, the flowers arranged in a raceme, panicle, umbel, fascicle, or sometimes flowers solitary; fruit drupaceous, fleshy to dry, but not regularly dehiscent along sutures.
20 Flowers bearing petals, the inflorescence variously shaped (flowers occasionally solitary); plants of various inland and coastal habitats.
(c) Steven, Daniel - C, permission granted to NCBG
(c) Horn, Jay
(c) Bradley, Keith
(c) Wright, Janet - CC-BY-NC, permission granted to NCBG
(c) Bradley, Keith
22 Inflorescence either an axillary umbel, cyme, or fascicle (or reduced to solitary) or an axillary compound inflorescence (panicle or compound cyme), with 2-3 orders of branching.
25 Fruit a fleshy and oily 1-seeded drupe; flowers 3-merous, with separate and undifferentiated perianth segments; fresh plants strongly aromatic; inflorescence compound, a panicle or compound cyme (with 2-3 orders of branching); [Basal Angiosperms]
25 Fruit a fleshy (but not oily) 1-8-seeded drupe, a berry, or a 2-4-locular capsule; flowers 4-8-merous, with differentiated sepals and petals, the petals usually basally fused; fresh plants not strongly aromatic; inflorescence an axillary umbel or fascicle (or reduced to solitary), a central axis absent or < 1 cm long; [Eudicots].
28 Plants armed with nodal thorns; stamens 5 and staminodia 5, epipetalous; fruit a berry or drupe with 1 seed;flowers 5-merous
1 Leaves deciduous.
30 Juncture of petiole and leaf blade eglandular, but the uppermost 1-3 mm of the petiole swollen into a prominent upper pulvinus; corolla bilaterally symmetrical, with 5 petals, pink to purple (rarely white in some cultivars); flowers bisexual; fruit an oblong, flat legume, 6-10 cm long; main palmate leaf veins 5-7 (-9)
29 Leaf base cuneate, rounded, truncate, subcordate, or auriculate (with 2 small “earlobe-like” lobes at the base of the leaf blade), with 1 (mid) vein from the base (3 veins from the base in Celtis in CANNABACEAE); leaf blade about as wide as long, or somewhat to much longer, 0.9-10× as long as wide.
31 Leaves 0.9-1.4× as long as wide (some taxa keyed in both leads).
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
32 Stipule scars not circumferential (or not apparent); flowers and simple fruits in inflorescences of 1-many flowers, axillary or terminal, but not simultaneously solitary and terminal; [Eudicots].
34 Petioles < 1 cm long; leaves various in shape, often acuminate at the apex and/or cuneate at the base, often with some tendency to toothing; hairs on foliage stellate (use at least 10× magnification), at least in part; inflorescence not conspicuously villous; fruit either a nut borne in a cup (acorn) or a dry, subglobose 3-valved capsule, with 1 seed.
36 Leaves glabrous, glabrescent or variously pubescent (including densely and silkily so, giving the leaf surface a shiny appearance), but not as above.
41 Pubescence of the foliage simple or absent (except stellate in STYRACACEAE); flowers bisexual, conspicuous, borne variously, but not in catkins (except in Leitneria); fruit various.
44 Flowers solitary; ovary superior; perianth either 3-merous and whorled or many-merous and spiraled; leaves mostly > 20 cm long and > 8 cm wide, distinctly broadest towards the apex (> 0.6× of the way from the leaf blade base to apex) (except Magnolia acuminata, which is sometimes both shorter, narrower, and broadest near the middle or towards the base); [Basal Angiosperms].
45 Flowers terminal, > 4 cm across, white, pale yellow, or pink; perianth many-merous, spiraled; fresh foliage not noticeably aromatic; fruit an aggregate of follicles; leaves cuneate or auriculate at the base; twigs with circumferential stipule scars at each node
46 Leaves with prominently parallel-arcing secondary veins; inflorescence a terminal corymb; leaves clustered at the tips of the twigs, thus appearing pseudo-whorled; trichomes of the leaf undersurface predominantly 2-branched (some simple) (use at least 10× magnification); flowers 4-merous; fruit a blue drupe; small tree
46 Leaves with secondary veins more obscure and complexly branching into tertiary veins; inflorescence axillary (often on the previous year’s wood), solitary to variously fascicled, clustered, or in racemes; leaves arrayed distichously along horizontal or arching twigs, not prominently clustered or pseudo-whorled (except often in Cyrilla in CYRILLACEAE, Symplocos in SYMPLOCACEAE, and Nyssa in NYSSACEAE); trichomes of the leaf undersurface either simple or stellate (or absent); flowers 4-5-merous; fruit a green, blue, or black drupe, an orange berry, or a green to brownish indehiscent capsule; small to large tree.
47 Pubescence of foliage and other parts stellate (use at least 10× magnification); petals 4-5, white, 10-25 mm long; fruit dryish, indehiscent, either longitudinally 2-4-winged or not winged
48 Leaves < 2.5 cm wide, dark green above, somewhat thickened, and tardily deciduous or semi-evergreen; fruit a dry, brownish, spherical drupe, 2-2.5 mm in diameter; inflorescence a narrowly cylindrical raceme with > 40 flowers
48 Leaves > 2.5 cm wide, usually medium-green above, herbaceous in texture, promptly seasonally deciduous; fruit a somewhat to very fleshy drupe or berry, > 5 mm in diameter; inflorescence a solitary flower or cluster, head, or irregular raceme of < 15 flowers.
49 Fruit a drupe (green when ripe), cylindrical to barrel-shaped, 8-12 mm long; leaves rather thick and leathery in texture, persistent into the winter, dropping tardily or at latest the following spring; flowers bisexual; stamens 30-50, in 5 fascicles
(c) Cressler, Alan M.
(c) Fleming, Gary P.
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
(c) Bradley, Keith