Ornamental · Fabaceae
Hairy Vetch
Vicia villosa
Sow it in fall and watch this nitrogen-fixing cover crop feed your soil all the way to spring.
Full sun
Every 7–14 days
180–240 days
USDA 4–8
Overview
Hairy vetch skips the pretty-plant routine and gets straight to work as a cool-season legume cover crop and green manure. It races out into a vine-like mat of fine, feathery leaves and grabs onto whatever it can climb, which is why growers keep pairing it with cereal rye to give it something to scale. Come spring it throws up violet-purple to blue-purple flowers just before the stand gets cut down.
The best part happens underground. As a legume it teams up with Rhizobium bacteria to pull nitrogen out of the air and bank it in root nodules, then hands that nitrogen right back when the plant is terminated and breaks down. A strong stand can deliver much of the nitrogen a following corn crop is after.
It earns its spot in the rotation, and two cautions keep it there. It is hard-seeded and reseeds fast, so it can spring up as a weedy volunteer if you let it set seed. And unlike laid-back clover, heavy grazing can poison cattle and horses, so treat it as a soil crop first and a forage a distant second.
Care
The short version: hand it full sun, well-drained ground, and seed inoculated with the right Rhizobium. Sow it in fall, let it fix nitrogen all winter, and cut it down at flowering before it sets seed.
Light
Hairy vetch thrives in full sun and still takes partial sun without much fuss. Pour on more light and you get a denser stand and more nitrogen fixed, so grab an open site whenever you can.
Water
Once it settles in, it laughs off dry, well-drained soil and rides on fall, winter and spring moisture, so you rarely need to water it outdoors. Waterlogging is the deal-breaker, since standing wet invites crown and root rot.
Soil
It powers along on well-drained sandy to loam soils and shrugs off low fertility and some acidity, though it likes a pH of 6.0 to 7.5. It barely wants nitrogen but does crave enough phosphorus, potassium and sulfur to really go.
Temperature
This is one hardy cool-season plant, tough through cold from about -20°F to 75°F (-29°C to 24°C). That winter grit is exactly what makes it such a champ of an overwintering cover crop across zones 4 to 8.
Humidity
Everyday outdoor humidity suits it fine, so there is no number to chase. Air movement counts for more here, since a crowded, damp stand is what lets crown rots dig in.
Feeding
As a legume it feeds itself, fixing its own nitrogen through Rhizobium nodules, so ditch the nitrogen fertilizer entirely. Inoculate the seed well and make sure the soil packs enough phosphorus, potassium and sulfur instead.
Pruning
Grown as an ornamental it needs zero pruning. As a cover crop the matching move is termination, mowing, rolling or crimping at flowering, or tilling it in, before it sets mature seed, so it releases nitrogen and skips the reseeding.
Repotting
none
Size & spacing
A stand rockets to 3 to 12 feet (90 cm to 3.7 m) of trailing growth, with each plant spreading about 2 to 6 feet (60 to 180 cm) as it scrambles over its neighbors. Sow it thick as a cover crop and it weaves into a dense mat rather than standing as separate plants.
When to plant
Hairy vetch runs on a fall-to-spring clock and rewards good timing. Sow it about 30 to 45 days before the killing frost so it roots before winter, let it idle through the cold, and terminate the stand the moment it flowers in spring to release its nitrogen and shut down 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 tracks back to three things: seed that reseeds, a stand that never got rolling, and wet-soil rots or spring aphids. Read the signs below and you can go after the cause instead of chasing the symptom around.
Vetch charging back as a weed in the next crop
This is hard-seed reseeding, the catch that comes with letting a stand run to maturity. About 10% to 20% of the seed wears a hard coat, so it hangs on in the soil for a season or more, then bursts up in your next grain or vegetable crop and pushes into field edges. Get ahead of it: cut the stand at flowering before any seed forms, then knock out the stray seedlings by cultivating or spot-treating them, always before they flower.
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 thin, pale stand that just won't fix nitrogen
Most often the trail leads straight to failed inoculation. Skip the right Rhizobium on the seed and hardly any nitrogen-fixing nodules form, leaving the plants yellow and sluggish. Sowing too late, loose seed-to-soil contact, waterlogged ground, or short phosphorus, potassium and sulfur pile onto the trouble. Dig a few roots and hunt for pink, active nodules, then inoculate with fresh vetch or pea Rhizobium, drive the seed in 30 to 45 days before killing frost, and clear up any drainage snag.
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
Wilting plants, rotting crowns, or aphids storming the shoots
Soggy ground throws the door open to root and crown rots like Sclerotinia, which turn up as soft, discolored tissue and white fuzzy growth at the base. Aphids crash the spring party too, packing onto tender new shoots and leaf undersides. Fight back the easy way: plant on well-drained ground, rotate away from legumes when rots build up, and put the lady beetles that vetch pulls in to work mopping up the aphids.
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 growing plant is low risk, and rabbits and birds take the leafy foliage in moderation just fine. The seeds carry mild toxins, so keep them out of reach. The big warning goes to 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
Grazing heavy vetch is the one to watch closely. Horses can develop hairy vetch toxicosis, bringing fever, skin sores, hair loss and weight loss, and a lush legume stand can also kick off bloat.
Livestock Caution
Cattle run into the very same danger horses do. Pile hairy vetch into their diet and it can trigger fatal granulomatous toxicosis, with fever, dermatitis, alopecia and weight loss, plus everyday legume bloat, so never turn stock onto pure or thick stands.
Cats Safe
The growing foliage stays low risk for a cat. Nibble a lot of plant or, more likely, get into the seeds, and the worst a cat runs into is a quick upset stomach, nothing dramatic.
Dogs Safe
Dogs land in the same easy spot as cats. Chewed leaves mostly just pass on through, though a dog that gulps down a mouthful of seeds can pick up some vomiting or a loose stool.
Rabbits Safe
A little leafy growth slots nicely into a mixed forage. Just keep the seeds out of reach, since they pack the plant's mild toxins.
Birds Safe
Foraging birds work the foliage without any bother. The seeds carry mild toxins, so they are not a feed to hand out on purpose.
People Safe
This is a field crop, not something for the plate. Handling it brings no real hazard, but the raw seeds and sprouts hold L-canavanine and are simply 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 handful of named selections turn up in the seed trade, most of them bred to boost winter survival and push spring maturity earlier.
'Purple Bounty'
A cold-hardy release built to power through northern winters and flower early, so you can terminate the stand sooner in spring.
'Purple Prosperity'
A companion to 'Purple Bounty' that overwinters reliably and matures early, handing you that same earlier spring termination.
Common vetch (Vicia sativa)
A related cover crop packing larger seed and less cold tolerance than hairy vetch, with seeds that 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 seed sown straight into the ground, and the right inoculant is the small move that makes all the difference.
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
Growing hairy vetch is a treat, and it starts with seed dropped straight into the ground in late summer to fall, about 30 to 45 days before the killing frost, so it can dig in before winter. Coat 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 teamed with cereal rye for support. The stand roots in fall, bides its time through winter, and then explodes back to life in spring once the warmth rolls in.
Myths
Vetches and legume cover crops are harmless grazing, just like clover.
Vetch might look like easy pasture, but it does not graze the way clover does. Hairy vetch shines as a nitrogen-fixing cover crop, yet its seeds carry L-canavanine and, in some vetch seed, cyanogenic compounds, and heavy grazing can cause hairy vetch toxicosis, a systemic granulomatous disease, along with bloat in cattle and horses. Run it as a soil crop, not safe pasture.