Mecardonia, commonly known as axilflower, is a genus of herbaceous flowering plants in the family Plantaginaceae, order Lamiales. The genus comprises around 31 described species, of which approximately 12 are currently accepted, and is placed within a family that also includes plantains, snapdragons, and speedwells.
Plants in this genus are procumbent and glabrous, forming low-growing mats with stems ranging from 5 to 40 cm in length. The leaves are ovate, 7–25 mm long and 3–16 mm wide, with crenate (scalloped) margins, and are borne on short petioles. A distinctive character is that the stems are 4-winged (alate). Dried specimens characteristically blacken.
The flowers are solitary and axillary, borne on pedicels 8–26 mm long and subtended by two small bracts at the base. The calyx has five unequal, imbricate lobes, nearly free to the base. The corolla is also five-lobed, 7–8 mm long, yellow with a purple throat and a bearded mouth — a combination that attracts small pollinators. Four fertile stamens are present. The fruit is an ovoid, loculicidal capsule 5–7 mm long, containing ovoid, reticulated seeds.
The genus was formally described by Hipólito Ruiz López and José Antonio Pavón (Ruiz & Pav.) and published in Florae Peruvianae, et Chilensis Prodromus in 1794. The type species is Mecardonia procumbens. A major taxonomic revision by Rossow (1987) recognised ten species; subsequent work identified additional species, including M. kamogawae from Argentina.
Several species, notably selections under the trade name "Magic Carpet Yellow," are cultivated as ornamental ground-cover annuals in temperate gardens.
Etymology
The genus name Mecardonia honours Antonio Meca y Cardona, an 18th-century Spanish patron who founded the botanical gardens in Barcelona in 1784. The genus was described by Spanish botanists Ruiz and Pavón and published in 1794.
Distribution
Mecardonia is predominantly distributed across South America — with five species recorded in Argentina — and the southeastern United States, particularly Florida and Alabama. The range extends northward along the US Atlantic coastal plain as far as Virginia.
Cultivation
Several Mecardonia selections, such as the 'Magic Carpet Yellow' series, are sold as ornamental garden plants for their low, spreading habit and bright yellow flowers. In temperate climates outside their native range they are typically grown as annuals.
Taxonomy Notes
The genus was described by Ruiz & Pav. (1794) with Mecardonia procumbens as the type species. Rossow's 1987 revision recognised ten species. Of the approximately 31 names that have been described, around 12 are currently accepted. GBIF records five accepted descendants under the genus. A new species, M. kamogawae, was described from Argentina as recently as 2011, indicating the genus is still being actively revised.
