Flora of the Southeastern United States
2022 Edition

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Key to Viburnum

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1 Leaves (at least the larger and better developed) palmately lobed and veined.
..2 Petioles lacking glands near its junction with the leaf blade; flowers all alike and fertile; twigs pubescent; fruit blue-black; [section Lobata]
..2 Petioles with several glands near its junction with the leaf blade; marginal flowers of the inflorescence sterile and much larger than the fertile central flowers (or in cultivated forms all the flowers sterile and enlarged); twigs glabrous; fruit red; [section Opulus].
....3 Ipper leaf surface glabrous; petiolar glands often > 2, mostly wider than tall, sessile, concave on the top; stipules slender-tipped; [alien, sometimes planted and escaped]
....3 Upper leaf surface strigose; petiolar glands usually 2, mostly taller than wide, stalked, rounded on the top; stipules thickened at the tip; [native, of n. WV, PA, and NJ northwards]
1 Leaves unlobed and pinnately veined.
......4 Lateral veins curving and branching repeatedly through most of their length, not noticeably parallel, the lateral veins becoming obscure in the general pattern of anastamosing veins and not obviously leading to marginal teeth; [section Lentago].
........5 Leaves entire or with a crenate margin, the teeth < 5 per cm of margin.
..........6 Leaves 2-5 cm long, obovate or spatulate, widest toward the tip; [of e. SC southward in the Coastal Plain]
..........6 Leaves 5-12 cm long, generally elliptic or ovate, widest at or below the middle; [collectively widespread and of various habitats].
............7 Peduncle (5-) avg. 13 (-25) mm long; leaves undulate-crenulate (or rarely entire); [Mountains and upper Piedmont]
............7 Peduncle usually 16-44 mm long; leaves entire (rarely somewhat undulate-crenate); [Coastal Plain, Piedmont, and low elevation boggy sites in the Mountains]
..............8 Peduncle usually 16-29 mm long; fruits pink to dark blue or black in late Jul-Aug; leaves smaller (usually 10-18 square cm); leaf blade avg. 6.1 × 2.0 cm; leaf apices acuminate to acute
..............8 Peduncle usually 33-44 mm long; fruits pale green to white in late Jul-Aug (later turning dark blue or black); leaves larger (usually 20-30 square cm); leaf blade avg. 8.3 × 3.8 cm; leaf apices acute to obtuse
........5 Leaves serrulate, the teeth > 5 per cm of margin.
................9 Leaves mostly strongly acuminate at the tip; [of sw. NC northward]
................9 Leaves acute, obtuse, rounded, or somewhat acuminate at the tip; [collectively widespread in our area].
..................10 Leaves herbaceous in texture, dull above (sun leaves slightly glossy); petioles and veins (lower surface) glabrous or slightly brown-scurfy; leaves elliptical (widest near the midpoint of the leaf); leaf apex usually acuminate; [widespread in our area, usually in bottomland or other mesic forests]
..................10 Leaves somewhat coriaceous in texture, glossy above (as if lacquered); petioles and veins (lower surface) red-scurfy; leaves mostly obovate (wider towards the apex); leaf apex often rounded (but variable); [of c. VA southward, usually in dry to dry-mesic woodlands and forests]
......4 Lateral veins of the leaves nearly straight and prominently parallel for most of their length, many of them forking near the margin, the ultimate veins leading to a tooth.
....................11 Winter buds consisting of tightly folded leaves uncovered by bud scales; plants strongly and noticeably stellate pubescent, especially on young parts and on the lower leaf surface; fruits red then turning black.
......................12 Leaves lanceolate, 3-5× as long as wide, entire; leaf base truncate to rounded; leaf surface strongly rugose; [section Viburnum]
......................12 Leaves ovate, 1-2.5× as long as wide, serrate; leaf base cordate; leaf surface planar to somewhat rugose.
........................13 Leaves 10-25 cm long, 8-20 cm wide, deeply cordate at the base; [native, of cool, high elevation forests and bogs]; [section Pseudotinus]
........................13 Leaves 5-12 cm long, 2-6 cm wide, rounded to cordate at the base; [alien, cultivated and escaping to suburban forests]; [section Euviburnum or Lantana].
..........................14 Marginal flowers of the inflorescence sterile and much larger than the fertile central flowers (or all the flowers sterile and enlarged)
..........................14 Flowers all alike and fertile.
............................15 >=Leaves coarsely and somewhat irrugularly serrate, the teeth usually 10-30 per leaf side
............................15 Leaves finely and evenly serrate, the teeth usually 40-50 per leaf side
....................11 Winter buds covered by bud scales; plants noticeably stellate-pubescent or not; fruits orange, red, or blue-black.
..............................16 Leaves oblong-obovate, wider toward the tip; inflorescence paniculate, with an elongate central axis, the lowest branches opposite and with other branches above; fresh leaves malodorous; [section Solenotinus]
..............................16 Leaves ovate or suborbicular, widest near or below the middle; inflorescence umbelliform, the main branches all attached at the same point; fresh leaves not malodorous.
................................17 Leaves with 8-12 lateral veins on each side; marginal flowers of the inflorescence sterile and much larger than the fertile central flowers; winter buds with 2 scales; [section Tomentosa]
................................17 Leaves with 5-9 lateral veins on each side; flowers all alike and fertile; winter buds with > 2, imbricate scales.
..................................18 Fruit orange or red; [aliens, planted and escaping]; [section Succodontotinus].
....................................19 Leaves broadly ovate, acute, pubescent on both surfaces
....................................19 Leaves ovate or ovate-lanceolate, acuminate, glabrous except for long, somewhat appressed hairs along the veins beneath
..................................18 Fruit blue-black; [native]; [section Mollotinus or Odontotinus].
......................................20 Petioles short, those immediately below a cyme ≤ 8 mm long.
........................................21 Cymes stipitate-glandular and pilose; leaf shape broadly ovate to rotund; [endemic to two small areas: Ozark and Ouachita Mountains of s. MO, AR, & e. OK and Appalachian Mountains of n. AL, sc. TN, & nw. GA]
........................................21 Cymes eglandular (occasionally sparsely glandular), and lacking eglandular hairs; leaf shape ovate; [more widespread]
......................................20 Petioles longer, those immediately below a cyme ≥ 10 mm long.
..........................................22 Cymes stipitate-glandular (occasionally glabrous in V. deamii).
............................................23 Leaf bases strongly cordate; [plants usually restricted to limestone substrates].
..............................................24 Leaf veins eglandular; leaves glabrate beneath or pubescent in axils; bark not exfoliating
..............................................24 Leaf veins stipitate-glandular; leaves tomentose abaxially (forma molle) to glabrate (forma leiophyllum); bark of stems and branches exfoliating
............................................23 Leaf bases cuneate, truncate, or occasionally subcordate; [plants of various substrates].
................................................25 Stipitate glands absent on petioles and leaf veins; stipules absent
................................................25 Stipitate glands present on petioles and leaf veins; stipules often present.
..................................................26 Petioles with simple or 2-pronged hairs; leaf shape ovate to broadly ovate; plants of dry soil
..................................................26 Petioles with stellate hairs and often also with simple hairs; leaf shape rotund; plants of moist-wet soils
..........................................22 Cymes eglandular (occasionally glandular in V. dentatum and V. scabrellum)
....................................................27 Petioles glabrous or glabrate; stellate hairs absent on leaves and petioles; hairs on leaf undersides confined to axils and a few veins; leaf shape usually ovate
....................................................27 Petioles sparsely to densely stellate pubescent; stellate hairs present on leaf underside and petiole, dense and soft to touch (V. carolinianum, V. scabrellum, most V. venosum) or sparse to moderate (V. dentatum, some V. venosum); leaf shape various.
......................................................28 Cymes not stellate pubescent (occasionally sparsely so); leaves thinner textured and with less prominent veins, sparsely to moderately stellate pubescent below; [plants relatively widespread]
......................................................28 Cymes stellate-pubescent; leaves thick textured and with prominent veins, moderately to densely stellate-pubescent below.
........................................................29 Leaf shape ovate to broadly ovate; leaf teeth 5-12 per side; upper leaf surface scabridulous with abundant simple hairs; [of the southern Atlantic and Gulf Coastal Plain]
........................................................29 Leaf shape rotund; leaf teeth 10-18 per side; upper leaf surface glabrate, not scabridulous; [of the Southern Appalachian mountains or the northern Atlantic Coastal Plain].
..........................................................30 Leaf underside densely pubescent and soft to touch (felt-like); stipular leaf bracts often present; fruits pubescent; leaf teeth 13-18 per side; [of the southern Appalachian mountains of w. NC, n. GA, and se. TN]
..........................................................30 Leaf underside moderately to densely pubescent and somewhat soft to touch (but not felt-like); stipular leaf bracts absent; fruits glabrous; leaf teeth 10-15 per side; [of the northern Atlantic Coastal Plain of se. MA, s. RI, and Long Island, NY]