306. Galinsoga Ruiz & Pavón, Fl. Peruv. Prodr. 110, plate 24. 1794.
Quickweed [For Mariano Martínez de Galinsoga, 1766–1797, court physician and director of the Botanic Garden, Madrid]
Judith M. Canne-Hilliker
Annuals, 2–62 cm. Stems erect. Leaves cauline; opposite; petiolate; blades (3-nerved) lanceolate to broadly ovate, margins entire or serrulate to serrate, faces glabrate to densely pilose. Heads radiate or discoid, in ± cymiform arrays. Involucres hemispheric to campanulate, 2.5–6 mm diam. Phyllaries persistent or falling, 6–9[–16] in 2[–3] series (elliptic, lance-ovate, oblong, or ovate, outer shorter, herbaceous or scarious, margins entire or minutely laciniate). Receptacles conic, paleate (paleae persistent or falling, scarious, proximal broadly elliptic to obovate, often connate at bases or nearly to apices, united in groups of 2–3 to adjacent proximal phyllary, each complex often enclosing and shed with a ray cypsela; distal persistent or falling, lanceolate to obovate, entire or 2- or 3-lobed, convex to conduplicate). Ray florets [0–](3–)5(–8)[–15], pistillate, fertile; corollas white or dull white to pinkish [purplish] (tubes pilose, laminae quadrate-obovate to oblong, lobes 0–3). Disc florets 5–50[–150], bisexual, fertile; corollas yellow, tubes (pilose) shorter than cylindric throats, lobes 5, deltate (anthers yellow; style-branch apices acute). Cypselae obconic to obpyramidal, glabrous or strigose (rays often shed with subtending phyllary plus 2–3 adjacent paleae); pappi 0, or persistent, of 5–20, white or gray, fimbriate, sometimes aristate scales. x = 8.
Species 15–33+ (2 in the flora): North America, Mexico, West Indies, Bermuda, Central America, South America; introduced in Europe, Asia, Africa, Atlantic Islands, Pacific Islands, Australia.
Galinsoga is closely related to Sabazia Cassini of Mexico and South America and to at least some members of Alloispermum Willdenow, primarily from South America. Galinsoga might best be treated as a single larger genus including Alloispermum and Sabazia (J. M. Canne 1978; J. L. Panero et al. 1999).
Canne, J. M. 1977. A revision of the genus Galinsoga (Compositae: Heliantheae). Rhodora 79: 319–389. Canne, J. M. 1978. Circumscription and generic relationships of Galinsoga (Compositae: Heliantheae). Madroño 25: 81–93.