Vetch belongs to the genus Vicia, which includes approximately 140 different species. When Vetch is intentionally planted, it is a highly beneficial agricultural tool, but when it appears uninvited, its rapid, sprawling habit makes it a challenging weed. The difference between a valuable cover crop and a problematic invader is determined by where it grows and how it is managed.
Understanding Vetch Species
The term “Vetch” typically refers to two main types encountered in North America: Hairy Vetch (Vicia villosa) and Common Vetch (Vicia sativa). Both are legumes characterized by weak, sprawling, or climbing stems that rely on adjacent structures for support. They utilize specialized, branched tendrils located at the tips of their compound leaves to cling to other plants or objects.
Hairy Vetch is identifiable by the dense, long hairs covering its stems and leaves. It produces clustered, pea-like flowers that are violet-blue. Common Vetch has a more vigorous spring growth habit and produces purple flowers. Both species develop pods that resemble small pea pods, which dry out and release numerous seeds.
Vetch as a Valuable Soil Builder
Vetch is highly valued as a leguminous cover crop, primarily for its exceptional ability to fix atmospheric nitrogen. The plant forms a symbiotic relationship with Rhizobia bacteria, which colonize root nodules and convert atmospheric nitrogen gas into plant-available forms, enriching the soil for subsequent crops.
Hairy Vetch, in particular, is one of the most effective legumes for this purpose, capable of fixing significant amounts of nitrogen annually. This fixed nitrogen reduces the need for synthetic fertilizer applications, benefiting high-nitrogen-demand crops like corn. When terminated, the Vetch biomass decomposes quickly due to its low carbon-to-nitrogen (C:N) ratio, rapidly releasing nutrients back into the soil.
The dense canopy of Vetch also serves as an effective form of weed suppression. When planted as a cover crop, it outcompetes early-season weeds for sunlight and water, and the resulting residue mulch smothers new growth. Vetch is also used as a high-protein forage crop for livestock.
When Vetch Invades Agricultural Land or Gardens
Vetch becomes a problem when its vigorous, vining growth habit enables it to climb and sprawl over neighboring vegetation, effectively smothering and shading out cash crops like small grains or strawberries. This competition reduces available light and nutrients, leading to decreased crop yields.
In agricultural systems, Vetch can volunteer from the previous year’s seed, creating an unwanted stand that competes directly with the planted crop. The plant produces a large number of seeds, often called “hard seeds,” which can remain viable and dormant in the soil for one or more seasons. This persistent seed bank and self-reseeding capacity is the primary mechanism by which Vetch transforms into a problematic, recurring weed.
Controlling Unwanted Vetch
Controlling Vetch requires interrupting its life cycle by preventing seed production.
Garden and Lawn Control
In small garden areas, hand-pulling is effective, especially when the soil is moist to ensure the entire taproot is removed. Mulching with materials like sawdust or black plastic can inhibit seed germination and suppress seedling growth.
In lawn settings, frequent mowing helps stunt the plant and prevent flowering and seed set. For more widespread infestations, a selective broadleaf herbicide containing active ingredients like 2,4-D can be used, as it targets the Vetch while sparing the surrounding grass. Applications of pre-emergent herbicides in the fall can prevent the germination of new Vetch seeds, which typically occur as a cool-season annual.
Agricultural Control
For larger agricultural fields, the most common management strategy is mechanical tillage before the plants flower in the spring. Turning the Vetch under the soil prevents the replenishment of the seed bank. Integrating Vetch control into a comprehensive crop rotation plan also helps manage its presence, ensuring it is terminated before it becomes an issue.