Ornamental · Fabaceae
Hairy Vetch
Vicia villosa
Sown in fall, this feathery nitrogen-fixing cover crop blankets the ground in green until spring.
Full sun
Every 7–14 days
180–240 days
USDA 4–8
Overview
Hairy vetch is a cool-season legume grown mostly as a cover crop and green manure, and up close it is all fine texture. Its slender stems sprawl into a low, vine-like mat of soft, feathery leaves, each one split into many small narrow leaflets, and it reaches out with thin tendrils to grip whatever it can climb, which is why it is so often laced through cereal rye. In spring the mat lifts one-sided sprays of violet-purple to blue-purple flowers above the greenery before the stand is cut down.
Beneath that feathery surface the real work goes on out of sight. As a legume it partners with Rhizobium bacteria that settle into small nodules along its roots, drawing nitrogen from the air and storing it there, then releasing it once the plant is terminated and breaks down. A dense green stand can hold much of the nitrogen a following corn crop needs.
The plant is handsome and useful, with two things to watch. It is hard-seeded, ripening tough seed inside gray-to-black hairy pods, and reseeds freely, so it can return as a weedy volunteer if left to mature. And unlike easygoing clover, heavy grazing of the leafy growth can poison cattle and horses, so it is a soil crop first and a forage a distant second.
Care
The short version: full sun, well-drained ground, and seed inoculated with the right Rhizobium. Sown in fall, its feathery green mat fixes nitrogen over winter and is cut down at flowering before it sets seed.
Light
Hairy vetch colors up best in full sun and still fills in under partial sun. More light builds a denser, deeper-green mat and fixes more nitrogen, so an open site brings out its fullest growth.
Water
Once rooted it takes dry, well-drained soil in stride, drawing on fall, winter and spring moisture, so it seldom needs watering outdoors. Standing water is what it cannot bear, since waterlogged ground softens the crown into rot.
Soil
It threads its roots through well-drained sandy to loam soils and tolerates low fertility and some acidity, favoring a pH of 6.0 to 7.5. It needs little nitrogen but wants enough phosphorus, potassium and sulfur to green up fully.
Temperature
This is a tough cool-season plant, its foliage holding through cold from about -20°F to 75°F (-29°C to 24°C). That hardiness lets its green mat survive as an overwintering cover crop across zones 4 to 8.
Humidity
Ordinary outdoor humidity suits it, so there is no figure to reach. Air movement matters more, since a crowded, damp tangle of stems is where crown rots settle in.
Feeding
As a legume it feeds itself, fixing its own nitrogen in the small root nodules, so nitrogen fertilizer is beside the point. Inoculate the seed well and see that the soil holds enough phosphorus, potassium and sulfur.
Pruning
Grown as an ornamental it needs no pruning. As a cover crop the parallel step is termination, mowing, rolling or crimping the flowering mat, or tilling it in, before the pods ripen, so it releases nitrogen and does not reseed.
Repotting
none
Size & spacing
A stand trails to 3 to 12 feet (90 cm to 3.7 m) of slender, climbing growth, each plant spreading its fine stems about 2 to 6 feet (60 to 180 cm) across its neighbors. Sown thickly as a cover crop, the feathery leaves knit into one continuous green mat rather than standing as separate plants.
When to plant
Hairy vetch runs on a fall-to-spring clock. Sow it about 30 to 45 days before the killing frost so the fine shoots root before winter, let the low green mat hold through the cold, and terminate the stand as its purple flowers open in spring to release its nitrogen and head off reseeding.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not started indoors; direct sown outdoors
- Plant: Late summer to fall, about 30 to 45 days before killing frost, to overwinter; often mixed with cereal rye for support
- Harvest: Violet-purple to blue-purple flowers in spring; terminate at bloom for green manure
Hardiness
USDA hardiness zones: 4–8
Temperature: down to -34°C
Troubleshooting
Most hairy vetch trouble shows in the plant itself: seedlings pushing up where they should not, pale washed-out leaves, or slumping stems and clustered aphids. Read the signs below and you can trace each one back to its cause.
Vetch seedlings pushing up again in the next crop
The trouble begins with hard-seed reseeding, the cost of letting a stand carry all the way to mature, gray-to-black hairy pods. Roughly 10% to 20% of that seed wears a hard, tough coat, so it lies buried and dormant for a season or longer, then breaks the surface as fresh green seedlings in your next grain or vegetable crop and creeps along the field edges. Cutting the stand while it is still in flower, before any pod ripens, stops the seed at the source, and the stray seedlings get cultivated or spot-treated before they bloom.
Fix:
- Terminate the stand at flowering, before mature seed forms, by mowing, rolling/crimping or tilling
- Cultivate or spot-treat volunteer seedlings before they flower
A sparse, yellowed stand with limp growth
When the fine leaves come up pale and washed-out instead of deep green, the cause is usually failed inoculation. Without the right Rhizobium on the seed, few of the small pink nodules form along the roots, and the plants stay yellow and slack. Sowing too late, loose seed-to-soil contact, waterlogged ground, or short phosphorus, potassium and sulfur deepen the pallor. Lift a few roots to look for those pink, active nodules, then inoculate with fresh vetch or pea Rhizobium, press the seed firmly into place 30 to 45 days before killing frost, and clear any standing water.
Fix:
- Inoculate seed with the correct vetch/pea Rhizobium before sowing
- Drill or firm seed for good soil contact and sow 30 to 45 days before killing frost
- Choose well-drained sites and correct P, K and sulfur deficiencies
Slumping stems, soft dark crowns, and clustered aphids
In soggy ground root and crown rots such as Sclerotinia set in, leaving the crown soft and discolored and dressing the stem base in a white, cottony fuzz. Aphids are the other spring sight, dense little clusters crowding the tenderest new shoots and the pale undersides of the leaves. A well-drained site keeps the tissue firm and dry, a rotation away from legumes eases the rots where they gather, and the lady beetles the flowers draw in pick the aphids off.
Fix:
- Improve drainage and avoid waterlogged sites
- Rotate away from legumes if soilborne rots build up
- Encourage lady beetles and other beneficials, which vetch attracts, to manage aphids
Toxicity
For cats, dogs and people the soft green plant is low risk, and the leafy foliage suits rabbits and birds in moderation. The small hard seeds carry mild toxins, so keep them out of reach. The real warning is for grazing animals: heavy hairy vetch can cause fatal toxicosis and bloat in cattle and horses, so never let livestock graze pure or thick stands.
Toxic to
Horses · Livestock
Safe for
People · Cats · Dogs · Rabbits · Birds
Horses Caution
Heavy grazing of the lush, leafy growth is the real hazard. Horses can develop hairy vetch toxicosis, marked by fever, raw skin sores, patchy hair loss and weight loss, and a thick legume stand can also swell the belly with bloat.
Livestock Caution
Cattle meet the same threat as horses. A ration weighted toward the leafy vetch can trigger fatal granulomatous toxicosis, with fever, inflamed skin, thinning coat and weight loss, on top of ordinary legume bloat, so pure or dense stands are never grazed.
Cats Safe
The soft green foliage is low risk to a cat. One that chews a good deal of leaf, or more often gets at the small round seeds, may show a brief upset stomach, and no more than that.
Dogs Safe
A dog fares much as a cat does. The chewed leaves usually slip through untouched, while a mouthful of the hard little seeds can bring on some vomiting or a loose stool.
Rabbits Safe
The tender leaves are fine in small amounts within a mixed forage. The small seeds carry the plant's mild toxins and are best kept well out of reach.
Birds Safe
Foraging birds pick through the foliage without harm. The seeds, small and hard, hold mild toxins and are not a feed to set out on purpose.
People Safe
This is a field crop, not a plate crop. Handling the leaves and stems poses no real hazard, though the raw seeds and pale sprouts hold L-canavanine and are not food.
The growing cover-crop foliage is low risk for pets; keep cats and dogs from gorging on plants and especially from eating the seeds. The greater hazard is to grazing livestock: do not let cattle or horses graze pure or heavy hairy vetch stands, which can trigger hairy vetch toxicosis and bloat.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
Only a few named selections reach the seed trade, most bred for better winter survival and earlier, showier purple flowering in spring.
'Purple Bounty'
A cold-hardy release bred to hold its green through northern winters and open its flowers early, which lets you terminate the stand sooner in spring.
'Purple Prosperity'
A companion to 'Purple Bounty' that carries its foliage reliably through winter and matures early for the same earlier spring termination.
Common vetch (Vicia sativa)
A related cover crop with plumper seed and thinner cold tolerance than hairy vetch, whose seeds carry the same vetch toxicity concerns.
Companions
Hairy vetch pairs best with a sturdy grain it can climb and a heavy feeder that wants the nitrogen it leaves behind, and worst with the winter grains it can contaminate by reseeding.
Plant near
Cereal rye: Rye provides a sturdy structure for the climbing vetch tendrils to scramble up, improves weed suppression and residue, and balances the nitrogen contribution
Corn: Hairy vetch terminated in spring supplies a large flush of fixed nitrogen that can partially replace fertilizer for a following corn crop
Keep apart
Winter wheat or other winter grains: Hard-seeded vetch readily reseeds and becomes a contaminating volunteer weed in winter grain crops
How to propagate
Hairy vetch grows one way, from small hard seed sown straight into the ground, and the right inoculant is what turns those seeds into a deep green, well-nodulated stand.
SeedEasy
Late summer to fall, about 30 to 45 days before killing frost, for overwintering · Establishes in fall, grows slowly over winter, then accelerates in spring
Hairy vetch begins as small hard seed pressed straight into the ground in late summer to fall, about 30 to 45 days before the killing frost, so the young feathery shoots can root before winter. Dust the seed with the proper Rhizobium first, then drill it at roughly 15 to 20 lb per acre or broadcast 25 to 30 lb per acre, often laced through cereal rye for support. The stand sends down roots in fall, holds its low green mat through winter, and stretches and climbs again in spring as the days warm.
Myths
Vetches and legume cover crops are harmless grazing, just like clover.
Its soft, feathery leaves look as gentle as any clover, yet hairy vetch does not graze the same way. This fine nitrogen-fixing cover crop carries L-canavanine in its seeds and, in some vetch seed, cyanogenic compounds, and heavy grazing can bring on hairy vetch toxicosis, a systemic granulomatous disease, along with bloat in cattle and horses. Read it as a soil crop, not safe pasture.