Lessingia is a genus of annual flowering plants in the daisy family (Asteraceae), order Asterales, native to western North America. The genus comprises around 14–20 species, the great majority of which are endemic to California, with a few extending into Arizona and Nevada.
Plants are taprooted annuals typically growing 2–90 cm tall. Stems are erect or decumbent and may be simple or branched from the base or distally, ranging from glabrous to villous or woolly. Leaves are alternate, basal and/or cauline, with blades that are 1-nerved and variable in shape — from ovate or obovate to lanceolate, linear, or subulate — with margins entire or dentate to pinnately lobed. Many species bear stipitate or sessile glands on stems, leaves, and phyllaries.
Flower heads are discoid (lacking true ray florets), though peripheral disc florets are sometimes enlarged and spreading, giving a superficially daisy-like appearance. Heads are borne singly or in corymbiform arrays, with hemispheric to narrowly cylindric involucres 4–13 mm in diameter and 10–55 phyllaries arranged in 4–8 series. Disc florets number 3–40 per head and produce white, pink, lavender, or yellow corollas. Fruits are cuneiform to linear cypselae bearing persistent pappi of barbellate bristles. Base chromosome numbers are x = 5 and x = 6.
Notable members include Lessingia germanorum (San Francisco lessingia), a federally endangered species restricted to San Mateo County, California, and Lessingia nemaclada (slenderstem lessingia) and Lessingia nana (dwarf lessingia), both widespread in the California interior. Some taxa formerly placed in Lessingia have been transferred to related genera including Benitoa, Corethrogyne, and Lessingianthus.
Distribution
Lessingia is native to western North America, with most species restricted to California. The range of individual species varies from narrow endemics confined to one or two counties — such as L. germanorum in San Mateo County — to more widespread taxa occurring from the Sierra Nevada foothills south to Kern County and extending into Arizona and Nevada.
Ecology
Lessingias are annual herbs adapted to open, often disturbed habitats in California's diverse landscapes, including grasslands, chaparral edges, and rocky slopes. Their taprooted annual habit and tolerance for dry summer conditions reflect a Mediterranean-climate ecology characteristic of the California Floristic Province.
Taxonomy Notes
Lessingia was treated by Staci Markos in Flora of North America (vol. 20). The genus boundaries have shifted over time: species formerly included in Lessingia have been reassigned to Artemisia, Benitoa, Cacalia, Chrysolaena, Corethrogyne, Lessingianthus, and Vernonia. GBIF recognises it as an accepted genus in Asteraceae with approximately 20 descendants.
Conservation
Lessingia germanorum (San Francisco lessingia) is listed as an endangered species. Several other lessingias have highly restricted ranges within California, making the genus of conservation interest in the California Floristic Province, one of the world's biodiversity hotspots.
