Onobrychis, commonly known as sainfoins, is a genus of roughly 206 accepted species of perennial herbaceous plants in the legume family Fabaceae, order Fabales. Native to Eurasia, the genus has its greatest diversity in a belt stretching from Central Asia to Iran, where 56 species occur — 27 of them endemic. The Flora Europaea recognises 23 European species, and O. viciifolia (common sainfoin) has become naturalised across grasslands and roadsides in Europe and North America, particularly on calcareous soils.
Plants are typically erect or spreading perennial herbs. Leaves are pinnately compound, alternate, with 6 to 14 pairs of oblong to linear leaflets. The pale-pink to deep-rose flowers are borne in dense elongated racemes and bloom from June to September; they are a favoured nectar and pollen source for honey bees and solitary bees. Fruits are distinctive rounded, single-seeded pods that bear prominent spines or ridges in many species, an adaptation for epizoochorous dispersal — the spines catch in the fur of large mammals.
Sainfoins are highly nutritious as forage, valued for centuries as feed for heavy working horses. Unlike many legumes, they are rich in condensed tannins that protect dietary proteins from hydrolysis in the rumen, allowing absorption further along the digestive tract — a property that also reduces the risk of bloat in grazing animals. Plants develop a deep taproot conferring strong drought resistance, though they do not recover well from overgrazing. Suited to the arid steppe belt of Eurasia, sainfoins yield only one hay or seed crop per year and are challenging to establish as persistent pasture.
Etymology
The genus name Onobrychis derives from Ancient Greek ónos (ὄνος, "donkey") and brýkein (βρύκειν, "to eat greedily"), meaning roughly "devoured by donkeys" — a reference to the plant's excellence as forage for large herbivores. The common English name "sainfoin" comes from Old French sain foin ("healthy hay"), reflecting the plant's long reputation for both medicinal virtue and livestock-fattening properties. The 16th-century agronomist Olivier de Serres noted that the plant's name arose from "inordinate praise" for its medical and pastoral qualities.
Distribution
Sainfoins are predominantly Eurasian, spanning a range from the arid steppe belt of Central Asia and Iran (the centre of species diversity, with 56 species) westward across Europe to southern Sweden. They are characteristic of dry, open habitats: grasslands, agricultural margins, and wasteland, especially on calcareous or chalky soils. Onobrychis viciifolia has been introduced and naturalised in grasslands across many parts of Europe and North America.
Ecology
Several Onobrychis species serve as larval host plants for specialist Lepidoptera, including the case-bearer moth Coleophora colutella (recorded on O. saxatilis) and the Damon Blue butterfly (Polyommatus damon). The showy nectar-rich flowers attract honey bees (Apis mellifera) and a variety of solitary bee species, making sainfoins valuable components of pollinator-supporting grasslands. The spiny or ridged seed pods facilitate passive dispersal by attaching to the coats of large mammals.
Cultivation
Sainfoins have been cultivated as a forage and hay crop since at least the 16th century. They are best suited to well-drained, calcareous soils and tolerate drought well thanks to a deep taproot, but establish slowly and do not persist well under heavy grazing. Only one hay or seed harvest per year is typical. Onobrychis viciifolia is the principal cultivated species and is still grown to a limited extent as a bee-forage and low-bloat ruminant pasture crop.
