Hairy vetch is a plant that falls under the category of legume. Legumes are useful plants for many reasons. The main one is that they add beneficial nitrogen to your soil. Nitrogen is the most important element in soil in terms of gardening. You must have enough nitrogen or your plants simply won’t grow. It is used in the chlorophyll molecule, which makes plants green and takes in carbon dioxide and light to make food. There are many other elements that are important to have in your soil, many in trace amounts and others in larger quantities, but nitrogen is the number one, most crucial element.
In addition to enriching the nitrogen in your soil, hairy vetch can help stabilize banks and prevent erosion in unstable areas. It can be used as a winter cover crop and as pasture grazing for animals. It is used to smother summer weeds. It is grown with grains like rye, wheat, and oats to enrich the forage. Vetch and rye grown together is most common and produces a hay of good quality. When compared to other vetches, hairy vetch tolerates poor soil conditions and cold weather the best. It can even be used as a companion plant in your smaller garden plot.
Nitrogen is needed by your plants more than any other element. All of the proteins and other large molecules in the plant require nitrogen, so without it, you have no plant. Soils can often be depleted in nitrogen. This can happen when too much carbon is added to the soil. Organisms in the soil like earthworms use nitrogen to break down carbon compounds, leaving a nitrogen deficiency for the plants. A deficiency can also occur when a plot of land is used to grow plants over and over without a break or without an input of nitrogen.
You can correct a nitrogen deficiency in soil by using fertilizers or natural materials like manure, guano, compost, and fishmeal. This is often adequate for a small garden or plot, but if you are growing a field of crops for harvesting or for foraging, it is not feasible to mix in these materials. You also may prefer a natural solution to spraying on commercial fertilizers.
Hairy vetch can enrich your soil through a natural process called nitrogen fixation. There is plenty of nitrogen available around your soil, but not in a useable form. The air is made up of nearly 78 percent nitrogen, so there is enough for everyone. The problem is that the nitrogen in the air is not in the right form for your plants to use. Something has to happen between the air and the soil to make nitrogen ready for plants, and that is nitrogen fixation.
Enter legumes like hairy vetch, which have tumor-like structures growing on their roots called nodules. Rhizobia bacteria live in the nodules and turn nitrogen in the air into a form that is useable by plants. The nitrogen in the air is in the form of the nitrogen molecule, which is simply two atoms of nitrogen. The bacteria process this molecule and change it to ammonia and ammonium by adding hydrogen. This symbiotic relationship benefits the bacteria too. They get food from the plants’ roots.
There are many different kinds of legumes, and many of them are great for increasing the amount of useable nitrogen in the soil. Hairy vetch is a winter annual legume and one of the most productive at nitrogen fixation. There are other types of vetch plants, but hairy vetch is most widely used in farming. It grows slowly in the fall, but its roots grow throughout the winter and by spring, hairy vetch quickly grows into twelve-foot long vines. It will grow to about three feet tall unless it can be supported, and then it will climb. It can be a lot of biomass to deal with, but it is often worth the effort.
As a cover crop, hairy vetch can help to prevent erosion. Any amount of slope in a field can result in erosion when water flows down it. The damage can be serious, and a cover crop can minimize the losses significantly by holding the soil in place. Hairy vetch will also protect a field from erosion by wind by covering the soil and keeping it from being blown away.
Of course, if you have nitrogen-poor soil, this might be the main reason for you to plant hairy vetch for cover. To use as a cover crop in a field, plant it between the rows of crops. It will fix nitrogen in early spring. When you are ready to plant a summer crop, turn the vetch under to enrich the soil. You can even let animals graze on the vetch before turning it under and still expect to get a good amount of nitrogen into the soil.
In addition to improving the nitrogen content of your soil, hairy vetch will suppress the growth of weeds in the early part of the season. It grows so vigorously that it easily out-competes weeds. As the vetch dies back, this effect wears off, but it can give you a fighting chance against weeds at the beginning of the growing season. If you want to extend that weed control timeline, you can mix the vetch with crimson clover or rye.
If you need forage for your livestock, hairy vetch mixed with other plants is a great option. It grows quickly and well and is very hardy in cold weather. It improves your soil by enriching it with nitrogen while your animals forage. Hairy vetch also stands up well to trampling by the animals. For forage, hairy vetch is most often mixed with rye.
If you are a small-time gardener rather than a farmer or homesteader, hairy vetch can still be useful. It can act as a companion plant in your garden. For instance, some gardeners use hairy vetch with tomatoes. It makes a good alternative to rotating crops throughout the space in your small plot. Plant hairy vetch in the fall and let it take root over the winter. In early spring, it fixes nitrogen and adds the element to the soil and also keeps down weed growth. When the time to plant tomatoes comes, cut the vetch down to the ground and put the tomato plants in holes that you dig around the vetch residue. The remaining vetch helps to retain water in the soil.
While there are other plants that can offer many of the benefits that hairy vetch does, however the vetch has several advantages over these. It has more phosphorous than other types of winter cover. Phosphorous, like nitrogen, is an essential element for plant growth. Hairy vetch grows well in poor soils, partly thanks to its ability to fix nitrogen for itself. It grows quickly and vigorously, will tolerate a variety of conditions, develops roots over the winter, and remains hardy through cold weather.
Sow your hairy vetch seeds at the end of the summer or in early fall in soil that is moist. If the soil is loose or has grain stubble, it need not be plowed before sowing. Plow or cultivate if you are starting with a new, grassy field or have soil that is very heavy and firmly packed. There are many fungal infections that can attack hairy vetch, so consider getting seeds of a variety that is resistant.