Mazus is a genus of roughly 40 species of low-growing herbaceous plants in the family Mazaceae, order Lamiales. The genus was first described by João de Loureiro in Fl. Cochinch. (1790) and has at various times been placed in Scrophulariaceae and Phrymaceae before being segregated into its own family, Mazaceae.
Plants in this genus are relatively small herbs with stems that are terete (rarely quadrangular) and either erect or procumbent, often rooting from lower nodes to form creeping mats. Leaves are arranged in a basal rosette or opposite on the stem, with the uppermost leaves sometimes becoming alternate; the petioles are distinctively winged. Flowers are borne in one-sided (secund) racemes. Each flower has a funnelform or bell-shaped 5-lobed calyx and a strongly 2-lipped corolla with two longitudinal ridges (plaits) on the palate; the lower lip is 3-lobed and the upper lip 2-lobed. Four didynamous stamens are inserted on the corolla tube. The fruit is a compressed capsule enclosed within the persistent calyx, splitting loculicidally and releasing numerous small seeds.
The genus is distributed across temperate and subtropical Asia — with the greatest diversity in China (approximately 25 of the ~35–40 species) — and extends to Japan, Korea, the Indian subcontinent, Southeast Asia, and into Australia and New Zealand. Species typically grow in damp habitats in both lowland and montane settings. Well-known members include Mazus reptans (creeping mazus), widely cultivated as a low ground cover, Mazus pumilus (Japanese mazus), and Mazus stachydifolius.
Distribution
Mazus is centred on East and Southeast Asia, with the greatest species richness in China (about 25 of approximately 35–40 species); the genus also occurs across Japan, Korea, India, Mongolia, the Philippines, Vietnam, Malaysia, Indonesia, and Russia (Far East), with additional species native to Australia and New Zealand. Species favour damp habitats in lowland to montane regions.
Taxonomy Notes
Mazus was described by João de Loureiro in 1790 (Fl. Cochinch. 2: 385) and long treated within Scrophulariaceae, then Phrymaceae, before molecular studies supported its placement in the segregate family Mazaceae. The synonym Hornemannia Willdenow applies to the same genus. The Chinese common name 通泉草属 (tong quan cao shu) is used in Chinese botanical literature.
Cultivation
Several Mazus species, particularly Mazus reptans (creeping mazus) and Mazus pumilus (Japanese mazus), are grown as low-maintenance ground covers in temperate gardens, valued for their mat-forming habit and small 2-lipped flowers. They perform best in moist, partly shaded to sunny positions, consistent with the damp-habitat preferences of the genus in the wild.
