Lepidium L. is a large genus of flowering plants in the mustard family (Brassicaceae), comprising around 175–265 accepted species depending on the treatment consulted. Commonly called peppercress, peppergrass, pepperweed, or pepperwort, the genus was formally described by Linnaeus in 1753. The name derives from the Greek for "small scale," a reference to the genus's characteristic small, flattened, scale-like fruits (silicles).
Plants in the genus are typically herbs, usually erect or ascending, sometimes procumbent or prostrate, growing 15–50 cm tall. Leaves range from linear to elliptic, entire to deeply pinnatifid. Small, four-petaled white (occasionally yellow) flowers are borne in dense racemes, and the fruits are ovate to orbicular pods that are often flattened and notched at the apex. Stamens may number 2, 4, or 6 depending on the species.
Lepidium has a near-cosmopolitan distribution, occurring across the Americas, Europe, Africa, Asia, and Australia. The genus spans habitats from disturbed roadsides and agricultural fields to alpine meadows and desert margins. Several species are notorious weeds — L. draba (hoary cress) and L. latifolium (perennial pepperweed) are designated noxious weeds in numerous US states and parts of Australia, where their rhizomatous mats crowd out native vegetation and alter soil dynamics. At the same time, some Lepidium species are of significant human value: L. sativum (garden cress) is widely cultivated as a salad herb, and L. meyenii (maca) is an important Andean food crop with deep pre-Columbian roots.
Etymology
The genus name Lepidium is derived from the Greek word lepidion, meaning "small scale." This likely refers to the genus's characteristic flattened, scale-like fruits (silicles). An alternative etymology connects the name to historical folk uses of the plant in treating leprosy — a disease that causes skin scaling — though the fruit morphology explanation is more widely cited in botanical literature.
Distribution
Lepidium is one of the most widely distributed genera in the mustard family, occurring on every inhabited continent. It is particularly diverse in the Americas, Europe, and Australia. California alone supports 10 species. In the southwestern United States and Sonoran Desert region, over 50 species have been documented, including numerous endemics. In Switzerland, at least 9 species are recorded in the national flora database. The genus spans elevational ranges from lowland valleys and coastal areas to mid-elevation foothills and alpine zones. Several species — especially L. draba and L. latifolium — are now abundant well outside their Eurasian native range, having spread across western and central North America and parts of Australia where they are classified as noxious weeds.
Taxonomy
Lepidium L. was formally described by Carl Linnaeus in his Species Plantarum of 1753, placing it in the family Brassicaceae (Cruciferae), order Brassicales. The genus is accepted by Plants of the World Online (Kew) with 265 accepted species; GBIF records 449 descendant taxa including infraspecific entities; ITIS records approximately 120+ accepted species and varieties — reflecting ongoing taxonomic revision of the group. SEINet's flora treatments cite approximately 175 cosmopolitan species.
Related genus Aneurolepidium is not accepted by ITIS (treated as a synonym), while Tricholepidium is maintained as a separate accepted genus. Flora of North America and Gleason & Cronquist's Manual of Vascular Plants are among the primary taxonomic treatments used for North American species.
Ecology
Lepidium species occupy a wide range of habitats including disturbed ground, roadsides, agricultural fields, dry grasslands, and desert margins. Several species have adapted to spread as tumbleweeds, dispersing seed across open landscapes. Flowers attract insect pollinators, particularly bees and syrphid flies. Invasive species such as L. draba form dense rhizomatous mats that outcompete native vegetation and alter soil dynamics, reducing local biodiversity. The genus shows considerable morphological variation in growth form (erect to prostrate) and reproductive structures (2, 4, or 6 stamens), reflecting adaptation to diverse ecological conditions.
Cultivation
Most Lepidium species are not deliberately cultivated, and for invasive species such as L. draba (hoary cress) cultivation is actively discouraged. Where species are grown, they thrive in disturbed or well-drained soils and prefer full sun. They tolerate both clay and sandy substrates, and some are notably drought-resistant thanks to deep rhizomes. Lepidium sativum (garden cress) is the primary cultivated species, grown widely as a fast-maturing salad herb and sprouting green. Lepidium meyenii (maca) is cultivated at high altitude in the Peruvian and Bolivian Andes, mainly in Peru, and increasingly in China.
Propagation
Propagation is primarily by seed, sown in spring. Vegetative propagation by spring division is also possible for species with established rhizomes. The deep rhizomatous root systems of weedy species such as L. draba make eradication difficult, as plants readily regenerate from root fragments.
Uses
Lepidium sativum (garden cress) has been used as a salad green and culinary herb for centuries and is still widely cultivated for this purpose. All parts of edible Lepidium species are usable when cooked; raw leaves taste spicy and acrid with strong wild-mustard character, while seeds can serve as a pepper substitute when toasted. The plants are antiscorbutic (providing vitamin C), and seeds have traditionally been used as a remedy for flatulence and reportedly for fish poisoning.
Lepidium meyenii (maca) holds a distinct place in Andean culture. Its cultivation dates to at least 1700 BC in the Lake Junin region. Maca roots are highly nutritious — 60–75% carbohydrates on a dry-matter basis — and were historically traded for lowland staples such as maize and rice, and accepted as payment for Spanish colonial taxes. Traditional preparations include slow-roasting the root in underground pits (huatia), preparing sweet porridge with milk (mazamorra), and use in empanadas and soups. Commercial interest surged from the 1990s onward, with global export of maca flour and new products such as maca beer (KUKA Beer, launched 2010). By 2014 cultivation had extended to China, prompting Peruvian concerns about biopiracy. The plant's Quechua names include maca-maca, maino, ayak chichira, and ayak willku.
Conservation
Several Lepidium species face severe conservation pressure. L. oleraceum (Cook's scurvy grass), native to New Zealand and sub-Antarctic islands, is classified as near extinct following dramatic habitat loss. L. amissum (Waitakere scurvy grass) is recorded as extinct in New Zealand. Conversely, a number of species — particularly L. draba (hoary cress) and L. latifolium (perennial pepperweed) — are invasive outside their native Eurasian range and are listed as noxious weeds in numerous US states and parts of Australia, where management focuses on preventing spread and eradicating established populations.
