The term “tares” is an ambiguous name used to describe weedy plants that grow among cultivated crops, making them difficult to separate during harvest. Historically, the name referred to two distinct species: Common Vetch (Vicia sativa) and Darnel (Lolium temulentum). Correct identification is important for agricultural management, as these species have different growth habits and toxicity profiles. This guide focuses primarily on Common Vetch.
Identifying Common Tares: Physical Characteristics of Vetch
Common Vetch is a scrambling, annual legume identifiable by its unique leaf structure. Its leaves are pinnately compound, divided into multiple pairs of narrow, oblong, or lance-shaped leaflets growing opposite each other on a central stalk. A distinguishing feature is the presence of slender, branched tendrils that form at the tip of each compound leaf, allowing the vetch to climb and cling to surrounding vegetation for support.
The plant produces classic pea-shaped flowers, a defining trait of the Fabaceae family. These flowers are typically a vibrant pink to dark reddish-purple, though lighter or whitish variations can occur. Unlike some other legumes, Common Vetch flowers usually appear solitary or in pairs directly from the leaf axils, the point where the leaf joins the main stem. After pollination, the flowers yield small, flattened seed pods that resemble miniature pea pods, generally measuring between one and three inches in length. These pods transition from green to dark brown or black as they mature, eventually splitting open to release their rounded, dark-colored seeds.
Growth Habits and Habitat
Common Vetch is typically a winter annual, meaning it germinates in the fall, grows slowly through the winter, and produces seed before dying off in the late spring or early summer. Due to its vining nature, the plant exhibits a sprawling or clambering growth habit, often forming dense, tangled mats when it lacks vertical support. Its tendrils allow it to climb up cereal grains or other tall plants, which is why it frequently appears as a weed in fields of wheat or oats.
As a member of the legume family, Common Vetch forms a symbiotic relationship with soil bacteria, enabling the fixation of atmospheric nitrogen. This process naturally enriches the soil, which is why it is often deliberately planted as a cover crop or “green manure” in agricultural settings. Beyond cultivated fields, this resilient plant is commonly found growing in disturbed soils, along roadsides, in pastures, and in waste areas worldwide. Its dual role as both a beneficial cover crop and a persistent weed highlights its adaptability.
Distinguishing Tares from Look-Alikes
Accurately identifying Common Vetch requires differentiating it from other plants in the pea family, such as cultivated peas and clover. Garden peas (Pisum sativum) also have compound leaves and tendrils, but their leaflets are significantly larger and fewer in number compared to the numerous, smaller leaflets of Common Vetch. Cultivated peas generally produce larger flowers held further away from the main stem on longer stalks.
Distinguishing Vetch from Clover (Trifolium species) is easier by examining the leaves. Clover species are defined by their characteristic trifoliate leaves (composed of only three leaflets) and lack the grasping tendrils found on Vetch. Clover flowers also look entirely different, presenting as dense, rounded, or cone-shaped heads, rather than the separate, pea-shaped blooms of Vetch. Other Vetch varieties, such as Hairy Vetch (Vicia villosa), are look-alikes, but they are covered in much more hair and produce their flowers in long, dense, one-sided clusters called racemes, a clear contrast to the solitary or paired flowers of Common Vetch.
The Historical Context: Darnel
The name “tares” carries historical weight because in ancient texts, particularly the biblical Parable of the Tares, it referred to Darnel (Lolium temulentum). Darnel is a type of grass that evolved as a “Vavilovian mimic” of wheat, meaning it looks nearly identical to the cereal grain during its early growth stages. This close resemblance made it almost impossible for farmers to weed out the Darnel until the plants reached maturity.
The danger of Darnel came from its toxicity, as its seeds often contained alkaloids produced by an endophytic fungus living within the plant. Consumption of these contaminated seeds could lead to symptoms like dizziness, nausea, and visual impairment; the Latin name temulentum translates to “drunk.” While the term “tares” in modern agriculture refers to the non-toxic Common Vetch, the historical association with the poisonous Darnel provides context for the name’s original use as a symbol of dangerous impurity in a crop.