Ornamental · Fabaceae
Hairy Vetch
Vicia villosa
Tuck it into the ground in fall and this forgiving nitrogen-fixing cover crop quietly feeds your soil all the way to spring.
Full sun
Every 7–14 days
180–240 days
USDA 4–8
Overview
If you are new to cover crops, hairy vetch is a kind place to start. It is a cool-season legume grown mostly as a cover crop and green manure rather than for show, and it forgives a lot. It sprawls into a soft, vine-like mat of fine, feathery leaves and reaches out to climb whatever it can find, which is exactly why so many growers give it cereal rye to lean on. When spring arrives it lifts up violet-purple to blue-purple flowers before the stand is cut back.
The magic really happens down in the soil, and you do not have to do much for it. Being a legume, hairy vetch teams up with Rhizobium bacteria to draw nitrogen from the air and tuck it away in root nodules, then hands that nitrogen back once the plant is terminated and begins to break down. A healthy stand can carry much of the nitrogen a following corn crop wants, which feels like a real win.
This plant gives generously, and it asks only that you keep two things in mind. It is hard-seeded and reseeds freely, so it can turn into a weedy volunteer if you let it set seed. And unlike easygoing clover, heavy grazing can poison cattle and horses, so treat it as a soil crop first and a forage only a distant second, and you will get along with it just fine.
Care
The short version: give it full sun, well-drained ground, and seed inoculated with the right Rhizobium. Sow in fall, let it fix nitrogen all winter, and cut it down at flowering before it sets seed. Mistakes here are easy to recover from.
Light
Hairy vetch is happiest in full sun, and it will take partial sun without much fuss. More light gives you a denser stand and more nitrogen fixed, so pick an open spot whenever you can.
Water
Once it settles in, it shrugs off dry, well-drained soil and leans on fall, winter and spring moisture, so you will rarely need to water it outdoors. The one thing it cannot forgive is waterlogging, which opens the door to crown and root rot.
Soil
It grows happily on well-drained sandy to loam soils and puts up with low fertility and a bit of acidity, preferring a pH of 6.0 to 7.5. It asks for very little nitrogen but does like enough phosphorus, potassium and sulfur to thrive.
Temperature
This is a wonderfully tough cool-season plant, hardy through cold from about -20°F to 75°F (-29°C to 24°C). That winter hardiness is just why it makes such a dependable overwintering cover crop across zones 4 to 8.
Humidity
Everyday outdoor humidity suits it fine, so there is no number to chase. Air movement matters more than moisture in the air, since a crowded, damp stand is what lets crown rots settle in.
Feeding
As a legume it feeds itself, fixing its own nitrogen through Rhizobium nodules, so you can skip the nitrogen fertilizer altogether. Just inoculate the seed well and make sure the soil holds enough phosphorus, potassium and sulfur.
Pruning
Grown as an ornamental it needs no pruning at all. As a cover crop the matching step is termination, mowing, rolling or crimping at flowering, or tilling it in, before the plant sets mature seed, so it hands over its nitrogen and does not reseed.
Repotting
none
Size & spacing
A stand climbs 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. Sown thickly as a cover crop, it weaves into a soft, dense mat instead of standing as separate plants.
When to plant
Hairy vetch keeps a gentle fall-to-spring rhythm, and it is hard to get badly wrong. Sow it about 30 to 45 days before the killing frost so it roots before winter, let it rest through the cold, and simply terminate the stand when it flowers in spring to release its nitrogen and head off any 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
Almost every hairy vetch hiccup comes down to one of three friendly-to-fix things: seed that reseeds, a stand that never quite got going, or wet-soil rots and spring aphids. Read the signs below and you will be able to treat the cause rather than chase the symptom, and get back on track.
Your vetch keeps returning as a weed in later plantings
Take heart, this is a common and manageable pattern called hard-seed reseeding, and it only happens when a stand is left to mature. Around 10% to 20% of the seed wears a hard coat that can rest quietly in the soil for a season or longer, then wake up in your next grain or vegetable crop and drift into field edges. You can stay ahead of it by cutting the stand down at flowering before any seed forms, and gently cultivating or spot-treating the few seedlings that slip through, well 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 thin, pale stand that gives back little nitrogen
Do not worry, this almost always traces back to failed inoculation, and it is easy to put right next time. Without the right Rhizobium riding along on the seed, few nitrogen-fixing nodules form, and the plants simply stay yellow and tired. Sowing too late, loose seed-to-soil contact, soggy ground, or thin phosphorus, potassium and sulfur can all pile on. Gently dig a few roots to look for pink, active nodules, then inoculate with fresh vetch or pea Rhizobium, settle the seed in 30 to 45 days before killing frost, and ease any drainage trouble.
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, soft rotted crowns, or aphids gathering on shoots
Wet, heavy ground is what usually opens the door to root and crown rots like Sclerotinia, which you will notice as soft, discolored tissue and white fuzzy growth low on the plant. The other spring visitor is aphids, which bunch up on the tenderest new shoots and the undersides of leaves. None of this needs to spoil your season: plant on well-drained ground, rotate away from legumes if rots start to build, and let the lady beetles vetch invites do the aphid work for you.
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
You can breathe easy around cats, dogs and people, for whom the growing plant is low risk, and the leafy foliage suits rabbits and birds in moderation. The seeds hold mild toxins, so simply keep them out of reach. The one firm 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
Here is where you do want to be careful. Horses grazing heavy vetch can develop hairy vetch toxicosis, bringing fever, skin sores, hair loss and weight loss, and a lush legume stand can also set off bloat.
Livestock Caution
Cattle share the same worry as horses, so this one needs real care. A diet leaning heavily on hairy vetch can bring on fatal granulomatous toxicosis, with fever, dermatitis, alopecia and weight loss, on top of everyday legume bloat, so never turn stock onto pure or thick stands.
Cats Safe
You can relax about the growing foliage, since it is low risk. If a curious cat nibbles a lot of plant or, more often, gets into the seeds, the worst you might see is a passing tummy upset, nothing to fear.
Dogs Safe
Dogs are in much the same happy position as cats. A mouthful of leaves usually just moves on through, though a dog that swallows a pile of seeds may have a little vomiting or a loose stool.
Rabbits Safe
A little of the leafy growth mixed into varied forage is perfectly fine. Just tuck the seeds out of reach, since those carry the plant's mild toxins.
Birds Safe
Foraging birds take the foliage in stride without any trouble. The seeds do hold mild toxins, so they are not something to set out for them on purpose.
People Safe
Rest easy, this is a field crop rather than food. Handling the plant poses no real hazard, though the raw seeds and sprouts contain L-canavanine and simply are not to be eaten.
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, and they were mostly bred to give you better winter survival and an earlier spring maturity.
'Purple Bounty'
You will find this cold-hardy release was bred to shrug off northern winters and flower early, which kindly lets you terminate the stand sooner in spring.
'Purple Prosperity'
A friendly companion to 'Purple Bounty', it overwinters dependably and matures early too, so you get that same welcome head start on spring termination.
Common vetch (Vicia sativa)
This related cover crop carries a larger seed and less cold tolerance than hairy vetch, and its seeds share the same vetch toxicity concerns to keep in mind.
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
There is really just one way to grow hairy vetch, from seed sown straight into the ground, and the right inoculant is the small step 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 could not be much simpler: sow the seed right into the ground in late summer to fall, about 30 to 45 days before the killing frost, giving it time to settle in ahead of 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 alongside cereal rye for support. The stand roots in fall, rests through winter, and wakes up again in spring as the days warm, so you will see the real growth then.
Myths
Vetches and legume cover crops make harmless grazing, just like clover.
It is easy to assume vetch grazes as gently as clover, but that is not quite the case. Hairy vetch is a wonderful nitrogen-fixing cover crop, yet its seeds carry L-canavanine 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. Think of it as a soil crop, not safe pasture.