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Hairy What - Hairy vetch that's what

© Arzeena Hamir

There are very few things that I like to plant in my garden that carry the name "hairy" but vetch is definitely one of them. Hairy vetch, Vicia villosa, is an annual legume that when planted as a cover crop, creates a lush layer of feathery leaves. It tolerates a wide soil pH range, from 4.9 to 8.2 but does best when pH is from 6.0 to 7.0.

The seeds are not very common so why do I go out of my way to plant it? In ideal conditions, hairy vetch can fix up to 100 lbs of nitrogen per acre and the soft leaves break down extremely fast, providing a boost to whatever crop is grown after it. If left on the surface during the growing season, the vetch will smother out any competing weeds and help to conserve moisture.

Hairy vetch grows well on most soil types, but is most adapted to loamy or sandy soils. Each plant produces from 3-10 stems, which vine their way over the soil, usually growing to 3ft in length. It is hardy up to Zone 4 and produces a purple flower that attracts many beneficial insects such as Seven-spotted lady beetles and big-eyed bugs.

Planting Directions

Most often, hairy vetch is planted as an overwintering cover crop and is seeded between July and mid-September. The earlier the seeding date, the more time the vetch has to establish a cover. Once temperatures drop below 50 degrees F, very little Nitrogen is fixed by the soil Rhizobia and it normally takes 3 weeks after planting for the nodules to form on the vetch roots. To ensure that the maximum amount of nitrogen is fixed, the seed should be coated with a pea/vetch inoculant prior to planting.

In states like Ohio & Minnesota where vetch will winter kill, it can either be planted as an early fall crop or seeding in the spring for a summer cover crop. When seeded in May, the plants will flower by July and can then be incorporated. When seeded in the spring, care does need to be taken around heat-loving crops since the cover that the vetch provides will actually cool the soil, slowing down growth for plants like cucumbers & peppers.

Here in the Pacific Northwest, a common practice is to mix hairy vetch with fall rye or oats. The cereal plants establish quickly and absorb any residual nitrogen that would otherwise be leached away during winter rains. In the springtime, the hairy vetch takes off and uses the rye or oat stems as a support to climb on. When both are turned over into the soil, the soft leaves of the vetch help to break down the more fibrous stalks of the cereals and allow nutrients to become available much faster. Research has shown that a combination of hairy vetch and rye or wheat would provide more winter soil cover and a larger yield of organic material than hairy vetch alone.