World of Weeds: Vexing Vetch

Originally published in Rural Delivery

One day last summer a friend was trying to describe a weed to me that was plaguing her garden. “It’s got purple flowers, and grows on long stringing stems, and tangled around all sorts of other plants in the garden,” she told me. I was mystified until she said that it sort of reminded her of tiny lupines, and then in a flash, I knew what she was talking about.

Vetch. Specifically, tufted vetch, also known as Vicia cracca according to our old friend Linneus, who made it his business to classify and name many many plants of our world. This wildflower with its needle-like compound leaves and blue-purple flowers on twining creeping stems is actually the first plant that I can remember from my childhood, having been fascinated with the pods of tiny black “peas” (seeds) that it produces after the flowers are spent. I distinctly remember eating the peas to see if they tasted good. d (they didn’t particularly, but they weren’t poisonous either. Despite the fact that I was maybe five or six when I tried this, I don’t recommend it to others as a way to launch into a career as an amateur botanist. Learn what plants are before you try dining on them!)

Vetch is a perennial weed grows in meadows, fields, along roadsides and in waste places, and also in gardens. Flowering time is from June until late August, although sometimes in mild autumns it continues to flower until frost.

It’s kind of neat that my friend should compare the flowers of vetch to those of lupines, because in actuality, they are related. Both are legumes, members of the pea family, and as a result both do something particularly useful to soil. Legumes, including peas and beans, clovers, birdsfoot trefoil and several garden perennials such as lupines, have little nodules on their roots which fix nitrogen, making it available in the soil for other plants to use. Nitrogen, as any gardener can tell you, is probably the most important element for plant growth, as it encourages the growth and development of vegetative parts of plants (leaves, stems, etc).

However, not every gardener or farmer appreciates the various vetches even though they do improve soil fertility. The problem with vetch is its growth habit. Give it an inch and it will take miles (never mind that tiresome metric conversion!) because it has spreading root systems that swarm eagerly throughout the soil. You may cut off the visible stems of a plant, and think you’ve got it all, only to find a week or so later several new shoots enthusiastically twining and winding their way through your perennial bed. Although it’s not considered a noxious weed in Atlantic Canada, there are certainly parts of North America where it is considered highly invasive. It can be problematic because it takes hold readily in disturbed soil, and can thus crowd out other species that are slower to germinate.

If you have vetch growing in your hayfield or pastures, don’t despair; it’s actually used as a forage crop in some areas, and it won’t hurt livestock. It’s also a plant that attracts both bees and butterflies, or, as I learned at a website on Russian Wild Nature, “This plant is fodder and nectariferous.” Certainly we see a fair number of fat, happy bees and flamboyant butterflies landing on the vetch around our property.

The key to control of vetch is to be rigourous in rooting it out—IF you don’t want it in your garden, that is. We’ve already talked about the role it plays in adding nutrients to the soil, and if your garden soil tends to be a bit on the poor side, some extra nutrients won’t hurt. You can even chop the plants up and dig them in, provided they’re not in flower—and don’t dig the roots in, nor put them in your compost heap! Vetch is actually considered a desirable plant in wildflower meadows, and there’s no denying it can be a charmingly pretty plant. In the perennial bed, where it wears out its welcome quickly, you need to dig out roots and all from the plant, and also mulch heavily in areas where you’ve had invasions of vetch, to prevent seeds from germinating. I have to confess that I’m not terribly diligent, however; I pull it out of the perennial bed when I see it, but leave it growing by the pasture and alongside the pond, where we let nature take its course.