Tithonia is a genus of flowering plants in the tribe Heliantheae within the family Asteraceae.
Tithonia has a center of distribution in Mexico but with one species extending into the Southwestern United States and several native to Central America. Two species, T. diversifolia and T. rotundifolia, are widely cultivated and have escaped to become weeds in tropical and subtropical areas around the world. T. rotundifolia makes a nice fresh cut flower, flowering in mid- to late-summer in the Northern hemisphere. The distinguishing feature of the genus is the peduncle, which is fistulose (meaning hollow and flaring toward the apex). The plants are coarse annual or perennial herbs or shrubs, and one species, T. koelzii, is a small tree.
Species
Plants of the World Online includes:
Tithonia brachypappa B.L.Rob. - San Luis Potosí
Tithonia calva Sch.Bip. - Durango, Sinaloa
Tithonia diversifolia (Hemsl.) A.Gray – tree marigold - Mexico, Central America; naturalized in Asia, Australia, Africa, South America, Florida, Texas, various oceanic islands
Tithonia fruticosa Canby & Rose - Chihuahua, Durango, Sonora, Sinaloa
Tithonia hondurensis La Duke - Belize, Honduras
Tithonia koelzii McVaugh - Jalisco
Tithonia longiradiata (Bertol.) S.F.Blake - Mexico, Central America (synonym T. pittieri (Greenm.) S.F.Blake)
Tithonia paneroi (B.L.Turner) E.E.Schill. & Panero
Tithonia pedunculata Cronquist - Oaxaca
Tithonia rotundifolia (Mill.) S.F.Blake - Mexico, Central America; naturalized in Florida, Louisiana, South America (synonym T. tagetiflora Desf.)
Tithonia thurberi Gray – Arizona sunflower weed - Chihuahua, Sonora, Arizona (Pima County)
Tithonia tubaeformis (Jacq.) Cass. - Mexico, Central America; naturalized in Argentina (synonym T. helianthoides Bernh.)
see Comaclinium, Enceliopsis, Lasianthaea, Viguiera
