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Published In: Species Plantarum 2: 906. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
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Project Data     (Last Modified On 8/10/2009)

 

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89. Rudbeckia L. (coneflower)

Plants annual or more commonly perennial herbs, mostly fibrous-rooted, less commonly with rhizomes or taproots. Stems erect or ascending, unbranched or few- to several-branched toward the tip, with several longitudinal lines or ridges, glabrous or variously hairy, slightly roughened to the touch. Leaves basal and alternate, the basal and lower stem leaves long-petiolate (except in R. missouriensis), the petioles progressively shorter up the stem, the upper stem leaves usually sessile or nearly so, the bases usually moderately expanded and more or less clasping or wrapping around the stem. Leaf blades simple, sometimes deeply ternately or pinnately lobed, those of the basal leaves usually ovate to elliptic-ovate (oblanceolate in R. missouriensis), those of the stem leaves variously linear to broadly ovate, tapered or rounded at the base, mostly angled or tapered to a sharply pointed tip, the margins otherwise entire or toothed, the surfaces glabrous or more commonly hairy (usually roughened), sometimes with sessile or impressed glands, with 1–5(–7) main veins. Inflorescences of solitary terminal heads, these sometimes appearing as loose, open clusters or leafy panicles, the heads mostly with relatively long stalks, these often with 1 or 2 bracts similar to the involucral bracts at or near the tip. Heads radiate (discoid elsewhere). Involucre broadly more or less saucer-shaped, the bracts in 1 or 2 subequal, overlapping series. Involucral bracts 5–25, linear to narrowly lanceolate or narrowly ovate, spreading to reflexed, green, the margins and outer (usually also the inner) surface roughened-hairy, not glandular, the midnerve inconspicuous. Receptacle nearly spherical to conical or less commonly somewhat cylindrical, often elongating somewhat as the fruits mature, with chaffy bracts subtending the disc florets (also the ray florets in R. amplexicaulis), these shorter than to slightly longer than the disc florets (including the corolla), concave and wrapped around the florets, truncate or rounded to angled or tapered to a sharply pointed tip, this unawned or with a soft, bristlelike awn, the apical portion green to dark purple, persistent at fruiting. Ray florets 5–21, sterile (lacking stamens and style at flowering and with an ovary that is shorter and thinner than those of the disc florets, not developing into a fruit), the corolla showy, relatively slender to somewhat broadened, spreading to drooping at flowering, yellow to orangish yellow, sometimes strongly reddish- or orangish-tinged toward the base, not persistent at fruiting. Disc florets 50 to numerous (more than 200), perfect, the corolla yellow, yellowish green, purple, or purplish brown, not thickened at the base, not persistent at fruiting. Style branches with the sterile tip somewhat elongate, tapered, and bluntly or sharply pointed. Pappus of the disc florets absent, a low rim or crown, or of 2–6 minute, unequal scales, usually persistent at fruiting. Fruits narrowly wedge-shaped to nearly oblong in outline, usually strongly 4-angled in cross-section, each face with several faint to more prominent but slender lines, grooves, or ribs, the angles sometimes very narrowly winged, the surface glabrous, brown to black, sometimes somewhat shiny. About 23 species, U.S., Canada; introduced in Europe.

A number of species of Rudbeckia are cultivated as ornamentals in gardens (Dress, 1961). A few species, such as R. hirta, also are sold as cut flowers. Native Americans used several species both topically and internally for a variety of ailments ranging from sores and burns to worms, snakebites, kidney disease, and heart problems. The foliage and stems of R. laciniata also were cooked and eaten by some tribes (Moerman, 1998). Species of Rudbeckia, especially R. laciniata, have been implicated in livestock poisoning. The active agents apparently belong to a group of sesquiterpene lactones. Burrows and Tyrl (2001) noted that experimental efforts to reproduce symptoms in pigs and sheep first reported anecdotally were only partially successful, with depression, loss of appetite, loss of coordination, and increased respiration apparently passing away relatively quickly without long-term effects. They also noted that because the plants have a strongly disagreeable flavor, livestock avoid eating them unless no alternative food plants are present.

Abrahamson and McCrea (1977) researched different patterns of absorption and reflectance of light in the ultraviolet portion of the spectrum on the corollas of R. hirta, R. laciniata, and R. triloba. A number of insects (such as bees) are able to see light in the ultraviolet portion of the spectrum, which is invisible to humans. The ultraviolet corolla patterns, which have been studied in a variety of plants, act as visual cues to attract appropriate pollinators.

 

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1 1. At least some of the leaves (at least the lower ones) with the blade ternately or pinnately lobed

2 2. Chaffy bracts as long as or slightly longer than the disc florets (including the corolla), tapered to a slender, sharply pointed, somewhat awnlike tip, glabrous ... 9. R. TRILOBA

Rudbeckia triloba
3 2. Chaffy bracts shorter than to nearly as long as the disc florets (including the corolla), truncate, rounded, or broadly angled to a short, bluntly or sharply pointed tip, the outer surface and margins with dense, short, often somewhat matted hairs

4 3. Stems glabrous, sometimes glaucous; leaf blades with the upper surface glabrous or sparsely hairy, smooth to the touch; disc corollas (and chaffy bracts) dull yellow to yellowish green ... 5. R. LACINIATA

Rudbeckia laciniata
5 3. Stems moderately to densely pubescent with short, spreading hairs, at least above the midpoint; leaf blades with the upper surface moderately pubescent with short, spreading, pustular-based hairs, roughened to the touch; disc corollas (and chaffy bracts) dark purple toward the tip (rarely greenish yellow) ... 8. R. SUBTOMENTOSA

Rudbeckia subtomentosa
6 1. All of the leaves with the blade unlobed, the margins entire, scalloped, or toothed

7 4. Stems and leaves glabrous, smooth to the touch

8 5. Stems 20–70(–90) cm long; stems and leaves not or only slightly glaucous, appearing green to somewhat bluish green when fresh; all but the lowermost leaves sessile and deeply cordate-clasping at the base; receptacle 10–30 mm long, 8–15 mm in diameter, hemispherical to ovoid or conical ... 1. R. AMPLEXICAULIS

Rudbeckia amplexicaulis
9 5. Stems (60–)80–250 cm long; stems and leaves strongly glaucous, appearing gray to bluish green when fresh; the median and uppermost leaves sessile and rounded to shallowly cordate-clasping at the base; receptacle 35–80 mm long, 15–35 mm in diameter, ovoid to conical or somewhat cylindrical ... 6. R. MAXIMA

Rudbeckia maxima
10 4. Stems and/or leaves sparsely to densely hairy, especially toward the stem tip, at least the leaves usually somewhat roughened to the touch

11 6. Plants often with taproots (sometimes with only fibrous roots), usually annual (occasionally resprouting the second year); pappus absent; stigma lobes elongate and more or less sharply pointed at the tip; chaffy bracts relatively long-fringed with spreading, bristly hairs toward the tip, the very tip with 1 or less commonly 2 bristles ... 4. R. HIRTA

Rudbeckia hirta
12 6. Plants without taproots, fibrous rooted (sometimes with somewhat fleshy roots), often with rhizomes or stolons, perennial; pappus present but sometimes minute; stigma lobes short and rounded to bluntly pointed at the tip; chaffy bracts glabrous or short-hairy, never with bristles at the tip

13 7. Chaffy bracts with the outer surface and margins densely pubescent with short, sometimes glandular or somewhat matted hairs toward the tip; ray florets with the corolla 30–50(–70) mm long, reflexed or strongly drooping at flowering; receptacle (10–)14–30 mm long, ovoid to conical ... 3. R. GRANDIFLORA

Rudbeckia grandiflora
14 7. Chaffy bracts with the outer surface glabrous (rarely with a few short hairs), the margins glabrous or with a fringe of minute hairs toward the tip; ray florets with the corolla 10–40 mm long, spreading to slightly drooping at flowering; receptacle 6–16 mm long, hemispherical to spherical, ovoid, or short-conical

15 8. Chaffy bracts as long as or slightly longer than the disc florets (including the corolla), tapered to a slender, sharply pointed, somewhat awnlike tip, the margins glabrous ... 9. R. TRILOBA

Rudbeckia triloba
16 8. Chaffy bracts shorter than to nearly as long as the disc florets (including the corolla), rounded or short-tapered to a broadly triangular, bluntly or sharply pointed tip

17 9. Leaf blades relatively broad, those of the basal leaves 10–110 mm wide, long-petiolate and lanceolate to ovate or somewhat heart-shaped, those of the stem leaves (5–)12–50(–70) mm wide, lanceolate to elliptic or ovate; plants with stolons, the new basal rosettes occurring at the stolon tips and often at some distance from (not immediately adjacent to) the older stems ... 2. R. FULGIDA

Rudbeckia fulgida
18 9. Leaf blades relatively narrow, those of the basal leaves 5–20 mm wide, more or less sessile to short- or less commonly long-petiolate and broadly linear to oblanceolate or narrowly spatulate, those of the stem leaves 4–10 mm wide, linear to narrowly oblong-lanceolate; plants with rhizomes, the new basal rosettes occurring close (immediately adjacent) to the older stems ... 7. R. MISSOURIENSIS Rudbeckia missouriensis
 
 
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