Tithonia

Desfontaines ex Jussieu

Gen. Pl., 189. 1789.

Common names: Sunflowerweed
Etymology: From Greek mythology, Tithonus, son of Laomedon and consort of Aurora, symbolic of old age perhaps alluding to gray to white induments of some plants
Treatment appears in FNA Volume 21. Treatment on page 138. Mentioned on page 135.
 TaxonIllustrator 
FNA21 P23 Sclerocarpus uniseria.jpegSclerocarpus uniserialis
Tithonia thurberi
Simsia calva
Linny Heagy
Yevonn Wilson-Ramsey
Yevonn Wilson-Ramsey

Annuals, perennials, subshrubs, or shrubs [trees], 70–500 [–700] cm. Stems erect, branched. Leaves all or mostly cauline; opposite (proximal) or mostly alternate; petiolate or sessile; blades often (1-), 3-nerved, or 5-nerved, mostly deltate or pentagonal [lanceolate, linear], sometimes 3-lobed or 5-lobed, bases ± truncate or auriculate [attenuate] (sometimes decurrent onto petioles), ultimate margins serrate to crenate, faces glabrate, ± hirsute, pilose, soft-pubescent, or villous, often glanddotted. Heads borne singly (peduncles usually distally dilated, fistulose). Involucres campanulate to hemispheric, 10–20+ mm diam. Phyllaries persistent, 12–28+ in 2–5 series (linear to broadly rounded, unequal to subequal, apices acute to rounded). Receptacles hemispheric to convex, paleate (paleae persistent, embracing cypselae, striate, ± 3-toothed, middle teeth larger, stiff, acute or acuminate to aristate). Ray-florets 8–30, neuter; corollas yellow or orange. Disc-florets 40–120 [–200+], bisexual, fertile; corollas yellow, tubes shorter than throats (bases of throats bulbous and hairy), lobes 5, ± triangular (anthers black, brown, or tan, bases cordate-sagittate, appendages ovate; style-branches relatively slender, appendages penicillate or lanceolate to attenuate). Cypselae (black or brown) ± compressed or flattened, often 3-angled or 4-angled or biconvex, ± cuneiform in silhouette (sometimes with basal elaiosomes); pappi 0, or ± coroniform (of ± connate scales, 1–2 scales sometimes subulate to aristate). x = 17.

Distribution

sw United States, Mexico, Central America, in se United States, West Indies, South America, and Old World

Discussion

Species 11 (3 in the flora).

Key

1 Perennials, subshrubs, or shrubs; phyllaries 16–28; ray laminae 48–69 mm; disc florets 80–120+; cypselae 4–6 mm Tithonia diversifolia
1 Annuals; phyllaries 12–16; ray laminae 9–15 or 20–33 mm; disc florets 40–60 or 60–90; cypselae 5–9 mm > 2
2 Leaf blades ± deltate to pentagonal, often 3- or 5-lobed, abaxial faces soft-pubescent; rays usually orange, rarely yellow, laminae 20–33 × 6–17 mm Tithonia rotundifolia
2 Leaf blades mostly deltate, rarely, if ever, lobed, abaxial faces sparsely hirsute (hairs larger on veins); rays yellow, laminae 9–15 × 4–6 mm Tithonia thurberi
... more about "Tithonia"
not tailed +, rounded +  and obtuse +
pale +  and dark +
connate +  and distinct +
subequal +
scarious +
usually ovate +  and lanceolate +
usually deltate +  and lanceolate +
indeterminate +  and determinate +
John C. La Duke +
Desfontaines ex Jussieu +
auriculate +  and truncate +
5-nerved +  and 3-nerved +
5-lobed;3-lobed;pentagonal;deltate +
winged;ribbed;winged;ribbed +
tuberculate +  and rugose +
barbellulate +  and barbellate +
Sunflowerweed +
yellow +  and orange +
hairy +  and glabrous +
cuneiform +, biconvex +, 4-angled +, 3-angled +, flattened +  and compressed +
fertile +  and bisexual +
fertile +  and bisexual +
sw United States +, Mexico +, Central America +, in se United States +, West Indies +, South America +  and and Old World +
From Greek mythology, Tithonus, son of Laomedon and consort of Aurora, symbolic of old age +  and perhaps alluding to gray to white induments of some plants +
villous +, soft-pubescent +, pilose +, hirsute +  and glabrate +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
indeterminate +
homogamous +  and heterogamous +
each +  and sessile +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
campanulate;hemispheric +
sessile +  and petiolate +
alternate +  and opposite +
triangular +
dentate to pinnatifid or palmatifid +  and entire +
2-carpellate +
persistent +
coroniform +
12 +  and 28 +
bearing subulate enations +, hairy +  and bristly +
hemispheric;convex +
la1982a +
exalbuminous +
appendaged +  and truncate +
hirsutulous +  and glabrous +
papillate +
Undefined (tribe Undefined) subtribe Lagasceinae +
Tithonia +
Asteraceae (tribe Heliantheae) subtribe Helianthinae +
cylindric +
serrate +  and crenate +
perennial +  and annual +
500 cm5,000 mm <br />5 m <br /> (700 cm7,000 mm <br />7 m <br />) +
shrub +  and subshrub +