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Published In: Icones et Descriptiones Plantarum 1(1): 9–10, pl. 14. 1791. (16 Feb 1791) (Icon.) Name publication detail
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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68. Cosmos Cav. (cosmos)

Plants annual (perennial herbs elsewhere), with taproots. Stems erect or ascending, unbranched or few- to several-branched, with several fine longitudinal lines or ridges, glabrous or sparsely to moderately pubescent, sometimes minutely roughened. Leaves opposite (basal leaves absent except in seedlings), variously sessile to long-petiolate, the bases slightly expanded and wrapping around the stem. Leaf blades 1 or 2 times pinnately lobed or dissected, all but those of the uppermost leaves oblong-ovate to oblong-elliptic in outline, the ultimate segments linear or oblong-triangular to oblong-lanceolate, tapered to a sharply pointed tip, the margins otherwise all or mostly entire, glabrous, minutely roughened, or sparsely pubescent with short, spreading hairs, the surfaces glabrous or sparsely and inconspicuously hairy or roughened, sometimes also dotted with sparse, sessile or impressed, yellow glands. Inflorescences of solitary terminal heads or appearing as loose, open clusters, the heads with long, bractless stalks. Heads radiate. Involucre narrowly cup-shaped to cup-shaped, the bracts in 2 dissimilar overlapping series. Involucral bracts fused at the base, variously shaped, glabrous but sometimes sparsely dotted with minute, impressed glands, inconspicuously 3- or 5-nerved, those of the outer series of (5–)8 green, slightly narrower and often slightly shorter than those of the often more scalelike inner series of (5–)8. Receptacle flat, not elongating as the fruits mature, with chaffy bracts subtending the ray and disc florets, these narrowly oblong to narrowly oblong-lanceolate, somewhat concave, sometimes wrapped around the florets toward the base. Ray florets (5–)8, 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 (except in C. parviflorus), 5–40 mm long, relatively broad, white, pink, purple, yellow, or orange, not persistent at fruiting. Disc florets 10–20 (–80 elsewhere), perfect, the corolla yellow to less commonly orange, not thickened at the base, not persistent at fruiting. Style branches with the sterile tip somewhat elongate and tapered. Pappus of the disc florets of 2–4 short awns (–8 elsewhere), these with downward-angled barbs, rarely very short or absent, when present then mostly persistent and somewhat spreading at fruiting. Fruits 7–30 mm long (including the beak), linear in outline (usually slightly curved and asymmetrically slightly thickened toward the midpoint), not or only slightly flattened, the body 4-angled in cross-section, tapered at the tip into an elongate, slender beak, each face with a slender longitudinal groove, the surface glabrous or sparsely hairy, sometimes appearing finely pebbled or roughened, dark brown to black, somewhat shiny. About 26 species, southwestern U.S., Mexico, Central America, South America, introduced nearly worldwide.

Several species of Cosmos are commonly cultivated as ornamentals in gardens, including two of the species in Missouri, C. bipinnatus and C. sulphureus. These two species also are components of so-called native wildflower seed mixes that were planted for roadside beautification in the past by the Missouri Department of Transportation and other public agencies (see also under Gaillardia pulchella, below). They are thus undoubtedly more widespread in the state than the few specimens in herbaria indicate.

 

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1 1. Ray florets with the corollas yellow to reddish orange; leaf blades lobed, the ultimate segments not threadlike, mostly 2–5 mm wide ... 3. C. SULPHUREUS

Cosmos sulphureus
2 1. Ray florets with the corolla white, pink, or purple; leaf blades deeply divided, the ultimate segments often threadlike, 0.5–1.5 mm wide

3 2. Ray florets with the corolla 1.5–4.0 cm long; fruits smooth or appearing minutely pebbled ... 1. C. BIPINNATUS

Cosmos bipinnatus
4 2. Ray florets with the corolla 0.5–1.5 cm long; fruits appearing minutely roughened (with minute, ascending teeth or hairs) ... 2. C. PARVIFLORUS Cosmos parviflorus
 
 
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