Onobrychis viciifolia Seeds | Sainfoin
LATIN NAME: Onobrychis viciifolia
COMMON NAME: Sainfoin
Plant Profile
Take the first cut at early to mid flower for hay, when the stems still hold leaf and the tannins are present. Wilt thoroughly, because the bulky stems dry slowly and a damp bale will heat. Regrowth comes from buds on the crown rather than from the cut stems, so leave a stubble tall enough to protect those buds. For grazing, strip-graze the aftermath and move animals on before they reach the crown; sainfoin stands persist for several seasons when the crown is not trampled. Hay from this crop is best fed to young stock and dairy animals, where the by-pass protein is worth the most.
Sainfoin seedlings compete poorly with broad-leaved weeds, so prepare the ground a season ahead or take a stale seedbed. Mow the young stand high to knock back annual weeds without cutting the growing points, and keep nitrogen low, since a rich soil only feeds the weeds and flattens the sainfoin.
Science & Biotechnology
The leaves and stems carry condensed tannins, proanthocyanidins built largely from prodelphinidin units. In the rumen these tannins bind soluble plant protein, slowing the burst of foam that causes frothy bloat in cattle on lush legumes, and they push part of that protein past the rumen so more of it is absorbed in the small intestine. Tannin levels fall as stems elongate, so the effect is strongest in leafy growth and weakest in over-mature hay. That single chemical trait is why sainfoin is grazed rather than feared.
The same tannins interfere with gastrointestinal nematodes, and sainfoin has been examined repeatedly as a grazing component that reduces the need for routine drenching. The mechanism is not a kill but a suppression of larval development and of worm fecundity, and the effect depends on how much leaf the animals actually eat. In practice sainfoin is used as part of a rotation or a mixed sward rather than as a stand-alone treatment.
Uses & Benefits
The French called this plant sain foin, healthy hay, and the name stuck because it did something no other fodder legume managed so cleanly: it filled animals without swelling them. On English chalk downs sainfoin was grown for centuries alongside lucerne as a premium hay, and it still holds its own where the ground is thin and dry and full of lime. The pink spikes were once a fixture of the downland skyline, and the crop returned the favour by feeding the bees that pollinated it.
The seed is sold inside the pod, a small semi-lunar husk with a toothed or spiny crest along the back, and each pod holds a single seed. That pod is the natural dispersal unit and the reason sainfoin seed is often sold as de-hulled material rather than clean seed. Common sainfoin and Russian sainfoin are frequently confused in trade listings: the Russian species is the harderier of the two, but the common type is the one with the deepest tannin profile and the more reliable performance on chalk. The plant is largely cross-pollinated, so seed crops need pollinators and isolation from other sainfoin stands.
Growing from Seed
Sainfoin is a calcicole. Its taproot descends far below the plough layer, which lets it finish a hay crop in a dry summer when shallower legumes have already stopped. It fixes nitrogen, but the partnership is fussy: the plant needs its own group of rhizobia and often nodulates poorly when sown onto ground that has never carried sainfoin, so an inoculant matched to the species matters more here than with vetch or clover.
Sow on a firm, clean seedbed in a shallow slot, covering the pod lightly; a coarse, cloddy tilth buries too much of it. Choose a site with free drainage and a neutral to alkaline reaction, and avoid ground that puddles in winter. Rolling after sowing settles the pods against moisture and discourages the small slugs that thin a young stand.
Our Take
Grow sainfoin where other legumes sulk: dry, limy, stony ground with sun on it. Inoculate, sow shallow, and be patient in the first season. For dry-land mixtures it works well with bird’s-foot trefoil, and crimson clover makes a fast winter cover on the same sort of soil while the sainfoin establishes. Where the ground is deeper, alfalfa is the higher-yielding but bloat-prone alternative, and the contrast in tannin chemistry is worth seeing for yourself.
Related Reading
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