Alfalfa, scientifically known as Medicago sativa, is a perennial flowering plant belonging to the legume family. It is widely cultivated across the globe, primarily for use as highly nutritious forage for livestock and as a source of hay. Identifying this plant in the field requires attention to several distinct physical characteristics that set it apart from similar species, particularly various clovers. This guide provides a detailed visual description of the plant’s structure, growth pattern, and reproductive features, assisting in clear identification.
The Distinctive Leaf Structure
The most immediate identifying feature of alfalfa is its unique leaf structure, which is classified as trifoliate, meaning each leaf comprises three separate small leaflets. These leaflets are typically oblong to ovate in shape, appearing slightly wider toward the tip than near the base. The leaflets are attached to the main petiole, but unlike many other trifoliate plants, the two lower leaflets are attached directly to the stem, while the third leaflet is slightly elevated on a short stalk.
A closer inspection of the leaflet margins reveals a specific pattern that helps differentiate alfalfa from true clovers. The edges are smooth along the lower two-thirds of the leaflet, exhibiting fine serrations or teeth only near the apex. At the very tip of the leaflet, there is often a short, distinct spur or tooth.
The leaflets usually display a uniform dark green color on the upper surface, often appearing slightly lighter underneath. The venation pattern is pinnate, with veins branching out from a central midrib and running toward the margins.
Alfalfa’s Growth Habit and Stems
Alfalfa plants exhibit an erect growth habit, rising vertically from a woody crown near the soil surface that facilitates regrowth after cutting. The stems are typically slender, somewhat hollow, and smooth, often branching out multiple times from the base as the plant matures. When fully grown, the plant usually reaches a height range of approximately one to three feet, depending on environmental conditions.
In a cultivated field, the dense stand of upright stems gives the plant a notably bushy appearance, maximizing light capture. This perennial persistence is supported by an extensive taproot system that can penetrate the soil deeply, sometimes reaching depths of 15 to 25 feet. The deep taproot allows the plant to access moisture and nutrients that are unavailable to many shallow-rooted annual plants, contributing to its drought tolerance.
The branching pattern and the rigidity of the stems allow the plant to stand upright in dense plantings without lodging. This structure is a direct result of its adaptation as a highly productive forage crop, designed to maximize light absorption and above-ground biomass production.
Flowers and Seed Pods
When alfalfa enters its reproductive phase, it produces small, clustered flowers that are distinctly pea-like in structure. These individual flowers are typically a vibrant purplish-blue color, though variations of white, cream, or pale yellow can occasionally be observed in certain specialized cultivars. The small blossoms are grouped tightly together on a short auxiliary stalk, forming an elongated cluster called a raceme.
Following successful pollination, the flower withers and develops into a distinctive seed pod. This pod is characterized by its small, tightly coiled or spiral shape, often completing two or three full turns. The pod’s appearance is often described as resembling a small, dry, tightly wound spring.
These spiral pods contain several small, kidney-shaped seeds, which are typically yellowish-brown when fully mature and dry. The unique twisting of the seed pod immediately distinguishes alfalfa from many other forage legumes that produce straight or slightly curved pods, such as clover. Identifying the combination of the purple raceme and the coiled pod confirms the plant’s identity.