Flora of the Southeastern United States
2022 Edition

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Key to Rudbeckia

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

1 Leaves grasslike, linear-lanceolate, never lobed, > 10× as long as wide, the basal with blade 10-20 cm long and < 1 cm wide; [of Coastal Plain, of s. GA southward and westward].
..2 Plant with 1 head; rays red, orange, or maroon, 1.0-1.5 cm long; plant pubescent
..2 Plant with several heads; rays yellow, 1.5-3.5 cm long; plant glabrous
1 Leaves broader, lanceolate, ovate, or pinnately-cleft, < 10× as long as wide; [collectively widespread].
....3 Leaves (at least some of the largest and generally more basal) 3-lobed or more divided (except R. laciniata var. heterophylla with sometimes few if any leaves lobed, and these usually the stem leaves).
......4 Disc flowers yellow or yellowish-green; achenes 3.5-6.0 mm long.
........5 Basal and lower stem leaves 1-2-pinnatifid, with 5-many lobes; plants 1-3 m tall.
..........6 Achenes 3.5-4.0 mm long; pappus 0.7-1.5 mm long; pales 3.1-4.1 mm long; [of e. VA, DE, MD, and PA northward]
..........6 Achenes 4.2-6.0 mm long; pappus 0.1-0.7 mm long; pales 4.4-6.1 mm long; [widespread in our area]
........5 Basal and lower stem leaves 1-5-lobed; plants 0.5-2 m tall.
............7 Heads larger, the disc mostly 1.5-2.0 cm wide; rays usually 8 or 13; [of high elevations of the Appalachians, VA and KY south to NC and TN]
............7 Heads small, the disc mostly 1.0-1.5 cm wide; rays usually 5 or 8; [of the Coastal Plain and Piedmont, VA south to FL, west to LA]
..............8 Leaves lobed; upper leaf surfaces moderately to densely hairy; [widespread in the Coastal Plain]
..............8 Leaves sometimes unlobed (basal leaves typically so); upper leaf surfaces sparsely to densely hairy; [of Levy County, FL]
......4 Disc flowers purple-brown; achenes 1.9-3.5 mm long.
................9 Pales acute, hairy near the tip; rays 20-40 mm long
................9 Pales cuspidate, with awn-like tips ca. 1.5 mm long, glabrous; rays 8-30 mm long.
..................10 Cauline leaves 1-3-lobed (at least some on a plant 3-lobed).
....................11 Ray blades 8-17 mm long; discs 10-15 mm across; [widespread in our area]
....................11 Ray blades 18-30 mm long; discs 15-20 mm across; [at moderate to high elevations in the Appalachians]
..................10 Cauline leaves 1-7-lobed (at least some on a plant 5-7-lobed).
......................12 Phyllaries > 9 mm long; [of the Mountains of NC, VA, and TN]
......................12 Phyllaries < 7 mm long; [of the Coastal Plain of s. AL and Panhandle FL]
....3 Leaves simple, unlobed, toothed (or entire).
........................13 Pales (bracts of the receptacle) densely pubescent near the tip.
..........................14 Plants glabrous or with scattered inconspicuous hairs.
............................15 Stem very sparsely spreading-villous (to more conspicuously hairy, and then keyable under 21b); disc to 15 mm high
............................15 Stem glabrous; disc elongating in fruit, ultimately 12-60 mm high.
..............................16 Leaves strongly blue-green and glaucous, strongly clasping stems.
................................17 Plants perennial; cypsela with pappi; rays yellow throughout; [typically in dry habitats]
................................17 Plants annual; cypsela lacking pappi; rays basally colored red-maroon; [typically in moist habitats]
..............................16 Leaves green, not glaucous, not strongly clasping stems.
..................................18 Blades of basal leaves 15-60 cm long, 2-8 cm wide, avg. 7× as long as wide; paleae 5-6 mm long, the apices acute to acuminate; achenes 3-5.5 mm long; [native of pitcherplant bogs and wet flatwoods of e. GA and ne. FL west to s. AL]
..................................18 Blades of basal leaves 15-50 cm long, 3-9 cm wide, avg. 5× as long as wide; paleae 6-8 mm long, the apices acute; achenes 5-7.5 mm long;; [native of coastal prairies and wetlands in LA and TX]
..........................14 Plants conspicuously hirsute or pilose.
....................................19 Plants perennials from a woody rhizome; pappus a low crown; style appendages short, blunt.
......................................20 Disc 10-15 mm across; rays 6-12, mostly spreading, 15-25 mm long; leaves not folded longitudinally
......................................20 Disc 15-25 mm across; rays 12-25, mostly reflexed, 30-50 mm long; leaves folded longitudinally.
........................................21 Stem hairy only on the upper stem, the hairs ascending and < 0.5 mm long
........................................21 Stem hairy throughout, the hairs spreading on the lower stem, ascending on the upper stem and ca. 1.0 mm long
....................................19 Plants annuals, biennials, or perennials from fibrous roots; pappus lacking or a low crown to 0.1 mm high; style appendages elongate, subulate (R. hirta) or short, acute to obtuse (R. mollis).
..........................................22 Stems and leaves softly pilose to woolly; style branches short, acute to obtuse; [plants of dry sands of the Coastal Plain of SC southward]
..........................................22 Stems and leaves with coarse and stiffish hairs; style branches elongate, subulate; [plants collectively widespread in our area].
............................................23 Stems leafy mainly toward the base, branched mainly near the middle; peduncles usually ½ the height of the plants; [of the Coastal Plain]
............................................23 Stems leafy throughout, branched mainly well above the middle; peduncles < 1/3 the height of the plants; [collectively widespread].
..............................................24 Basal leaves broadly elliptic to ovate, 2.5-7 cm wide, mostly ca. 2× as long as wide, with coarsely serrate margins; rays typically yellow or tinged orange throughout; [mostly undisturbed woodlands and fields, Appalachian highlands westward to IL]
..............................................24 Basal leaves lanceolate to oblanceolate 1-2.5 (-5) cm wide, mostly 3-5× as long as wide (or basal leaves absent), with entire to serrate margins; rays typically yellow with maroon, brown, or reddish bases; [disturbed areas OR glades and similar dry habitats, e. US westward].
................................................25 Plants annual; lacking basal tufts of leaves; cauline leaves with consistent size; lower leaves sessile or subsessile; [sandstone glades, other dry areas, IL and IN south to MS and TX]
................................................25 Plants biennial or short-lived perennials; with basal tufts of leaves; cauline leaf size gradually decreasing along stem; lower leaves petiolate; [disturbed areas, widespread]
........................13 Pales (bracts of the receptacle) glabrous or nearly so (except sometimes for a minutely ciliate margin).
..................................................26 Pales cuspidate, with awn-like tips ca. 1.5 mm long
....................................................27 Cauline leaves 1-3-lobed (at least some on a plant 3-lobed).
......................................................28 Ray blades 8-17 mm long; discs 10-15 mm across; [widespread in our area]
......................................................28 Ray blades 18-30 mm long; discs 15-20 mm across; [at moderate to high elevations in the Appalachians]
....................................................27 Cauline leaves 1-7-lobed (at least some on a plant 5-7-lobed).
........................................................29 Phyllaries > 9 mm long; [of the Mountains of NC, VA, and TN]
........................................................29 Phyllaries < 7 mm long; [of the Coastal Plain of s. AL and Panhandle FL]
..................................................26 Pales obtuse to acute.
..........................................................30 Larger leaves < 2 cm wide
..........................................................30 Larger leaves > 2 cm wide.
............................................................31 Stem leaves auriculate or auriculate-clasping.
..............................................................32 Plants 2-3 m tall; stem leaves strongly auriculate-clasping; paleae 4-6 mm; [sandy stream banks, wet roadsides in AL, FL, and GA]
..............................................................32 Plants 2 m tall or less; stem leaves weakly auriculate, not clasping; paleae 6-8 mm; [seepages in w. LA and e. TX]
............................................................31 Stem leaves petiolate or sessile, but not auriculate-clasping.
................................................................33 Basal leaves with bases cordate (some may be merely rounded); upper stem leaves notably reduced in size relative to the lower stem leaves.
..................................................................34 Paleae eciliate; rays 25-40 mm long
..................................................................34 Paleae ciliate; rays 15-25 mm long.
....................................................................35 Plants densely clonal, spreading by leafy stolons; lower stems coarsely angled in ×-section, 4-7 mm in diameter; basal leaf blades 9-20 cm long, 4-13 cm wide, 1.6-3.0× as long as wide; [saturated soils of seeps, fens, streambanks, and seepage swamps]
....................................................................35 Plants solitary, lacking leafy stolons; lower stems rounded or nearly so in ×-section, 1.5-3.0 mm in diameter; basal leaf blades 7.5-10 cm long, 5-6.5 cm wide, 1.0-1.6× as long as wide; [mesic soils of forests]
................................................................33 Basal leaves with bases cuneate to broadly cuneate or rounded; upper stem leaves similar in size to the lower stem leaves.
......................................................................36 Paleae ciliate.
........................................................................37 Stem leaves elliptic to ovate
........................................................................37 Stem leaves spatulate to oblanceolate
......................................................................36 Paleae eciliate (erose to minutely toothed, rarely with 1-2 cilia).
..........................................................................38 Leaves elliptic to ovate.
............................................................................39 Rays 6-12 mm long; stem leaves 1.5-2.0× as long as wide; stem and leaves with appressed soft hairs; flowering heads opening during mid-July to mid-August
............................................................................39 Rays 16-23 mm long; stem leaves 3-6x as long as wide; stem and leaves with spreading pustulate hairs; flowering heads opening during early August to mid-September
..........................................................................38 Leaves narrowly lanceolate to linear.
..............................................................................40 Stems and leaves nearly smooth; upper stem leaves entire or slightly toothed, auriculate at the base; [dry rocky glades and woodlands]
..............................................................................40 Stems and leaves hirsute; upper stem leaves coarsely toothed to laciniately lobed; [mesic to wet meadows, fens, marshes, and stream banks].
................................................................................41 Stems densely hirsute, the hairs retrorse; rays 15-25 mm long
................................................................................41 Stems sparsely hirsute, the hairs spreading; rays 20-40 mm long