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Published In: Species Plantarum 2: 886. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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

 

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78. Helenium L. (sneezeweed)

Plants annual or perennial herbs. Stems erect or ascending, sometimes from a spreading base, unbranched or few- to many-branched mostly above the midpoint, with fine longitudinal ridges and grooves, sometimes appearing winged, glabrous or variously hairy, sometimes also with small, sessile, spherical, yellow glands. Leaves alternate and sometimes also basal, sessile (the basal leaves occasionally with a short, winged petiole), the base extended downward along the stems as narrow wings of green tissue (except in H. amarum). Leaf blades linear to elliptic or narrowly ovate, unlobed, shallowly pinnately lobed, or (in H. amarum) deeply pinnately divided, mostly angled or tapered at the base, angled or tapered to a sharply or less commonly bluntly pointed tip, the margins otherwise entire, wavy or toothed, the surfaces variously glabrous or hairy, also dotted with relatively dense, sessile to impressed, yellow to yellowish brown glands, smooth or very slightly roughened to the touch. Inflorescences of solitary heads terminal on the branches or appearing as loose, open clusters or open, leafy panicles, the heads appearing mostly long-stalked. Heads radiate (discoid elsewhere). Involucre more or less saucer-shaped, the bracts in 2(3) unequal to subequal series, those of the outer series sometimes fused at the base. Involucral bracts 15–21, green with sometimes thinner, white margins, 1-nerved, spreading to more commonly reflexed at flowering, linear to narrowly triangular or narrowly lanceolate, the surfaces and margins glabrous to variously hairy and dotted with relatively dense, sessile to impressed glands. Receptacle strongly convex (hemispherical to broadly conical or nearly globose), often slightly enlarging as the fruits mature, naked. Ray florets 5–21 in usually 1 series (absent elsewhere), pistillate or sterile, the corolla relatively broad above a slender base, yellow, occasionally with reddish streaks or reddish-tinged toward the base, the tubular portion and the undersurface of the ligule with sparse to moderate, minute, curled hairs and also with moderate to dense, sessile and spherical or somewhat impressed, yellow glands, not persistent at fruiting. Disc florets 75 to numerous (more than 500), perfect, the corolla 1.5–4.0 mm long, yellow or reddish brown to dark purple, the tube not expanded at the base (but somewhat expanded above the base) or persistent at fruiting, glandular, the 4 or 5 sharply pointed lobes also glandular on the outer surface. Style branches with the sterile tip slightly expanded and more or less truncate. Pappus of 5–8 scales, these papery and white or thinner and nearly transparent, lanceolate to narrowly ovate, tapered to a short- or relatively long-awned or sharply pointed tip, the margins usually slightly irregular (toothed or fringed elsewhere). Fruits wedge-shaped to narrowly wedge-shaped in outline, 4–8-angled or ribbed, the surface moderately to densely pubescent with ascending hairs, at least on the angles or ribs, often also glandular, brown. About 35 species, North America to South America, Caribbean Islands.

Species of Helenium contain helenanolide sesquiterpene lactones, especially helenalin and tenulin, which render the plants bitter and toxic. Ingestion of significant quantities causes a condition known as spewing disease, first recognized in cattle grazing on other species in high-elevation pastures in the western states (Burrows and Tyrl, 2001). Symptoms include vomiting, diarrhea, and death. The bitter flavor of tenulin (the main compound in H. amarum) can also flavor milk from cattle that have grazed on these plants. Because livestock avoid ingesting Helenium species unless no other food sources are available, the genus (particularly H. amarum) is an indicator of overgrazed pastures.

 

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1 1. Leaf bases not decurrent, the stems not appearing winged; all linear to narrowly linear, unlobed or the lower leaves rarely deeply pinnately divided into linear segments; plants annual, with a taproot ... 1. H. AMARUM

Helenium amarum
2 1. Leaf bases decurrent as narrow wings downward along the stem; leaves narrowly lanceolate to elliptic-ovate, unlobed or the basal leaves sometimes with shallow pinnate lobes (these rounded, not linear); plants perennial, with fibrous roots

3 2. Ray florets sterile; disc florets with the corollas reddish brown to dark purple ... 3. H. FLEXUOSUM

Helenium flexuosum
4 2. Ray florets pistillate; disc florets with the corollas yellow

5 3. Leaves basally disposed, the basal and lower stem leaves significantly larger than the median and upper stem leaves, usually persistent at flowering ... 2. H. AUTUMNALE

Helenium autumnale
6 3. Leaves well developed along the stem, the basal and lower stem leaves usually somewhat smaller than the median ones, absent at flowering ... 4. H. VIRGINICUM Helenium virginicum
 
 
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