Flaveria trinervia is a species of flowering plant in the aster family known by the common names clustered yellowtops, speedyweed, and yellow twinstem. It is native to parts of the Americas, including the southeastern and southwestern United States (Florida, Texas, Arizona, New Mexico), most of Mexico, Belize, and parts of the Caribbean, but it is known in many other places as an introduced species and often a noxious weed, such as in Hawaii.
Flaveria trinervia grows easily in many types of wet habitats, including saline and alkaline soils and highly disturbed habitat. This is an annual herb growing erect and known to exceed two meters (7 feet) in height. The lance-shaped to oval leaves are each up to 15 centimeters (8 inches) long and arranged oppositely in pairs around the stem, their bases sometimes fused together. The edges of the leaves generally have tiny widely spaced teeth. The inflorescence is a large dense cluster of many very small flower heads, sometimes over 300 in one cluster. Each flower head contains 0-1 yellow or whitish ray floret and 0-2 yellow disc florets.
This plant exhibits C4 carbon fixation.
The Australian species F. australasica is very similar and possibly closely related to F. trinervia. Some authors treat the two as distinct species while others consider F. australasica as a synonym of F. trinervia.
- "The Plant List: A Working List of All Plant Species". Retrieved 23 December 2014.
- "GRIN Species Profile".
- Biota of North America Program 2014 county distribution map
- Powell, Albert Michael. 1979. Annals of the Missouri Botanical Garden 65(2): 628-629 description and commentary in English, distribution map on page 625
- Marin Life Photography photos in Hawai'i
- Flora of Zimbabwe
- Flora of North America, Flaveria trinervia (Sprengel) C. Mohr, 1901. Clustered yellowtops
- Powell, Albert Michael. 1979. Annals of the Missouri Botanical Garden 65(2): 629-630 description and commentary in English
- The Plant List, Flaveria australasica Hook.
- Atlas of Living Australia, Flaveria trinervia (Spreng.) C.Mohr
- Jepson Manual Treatment
- United States Department of Agriculture Plants Profile
- photo of herbarium specimen at Missouri Botanical Garden, collected in Nuevo León in 1848
- Discover Life
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