Alfalfa (Medicago sativa) is frequently mistaken for a type of grass, but it is correctly classified as a perennial flowering plant belonging to the Fabaceae, or legume, family. It is more closely related to peas and beans than to true grasses. Alfalfa is one of the world’s most widely cultivated forage crops, valued for its resilience and high nutritional content.
Defining the Key Visual Components
The most identifiable structure of the alfalfa plant is its leaves, which are arranged alternately along the stem. Each leaf is compound and trifoliate, consisting of three small leaflets. These leaflets are typically lance-shaped, oblong, or ovate and measure up to one inch in length. Small serrations appear only near the tip of each leaflet. The leaves are olive to blue-green, with some varieties exhibiting a subtle chevron pattern of lighter green lines on the upper surface.
The stems of alfalfa are numerous, slender, erect, and branching. They are generally hairless or covered with fine hairs and can reach a mature height of up to 36 inches (one meter). These stems originate from the crown, the base of the plant near the soil surface.
Alfalfa produces small, pea-shaped flowers that bloom in dense, short clusters called racemes, typically containing between five and 30 blossoms. The flowers are most commonly purple or blue-violet, though certain cultivars may display white or yellow. Each flower measures only about 0.2 to 0.4 inches long.
Following pollination, the plant develops the seed pod. These pods are small, coiled, and spiral-shaped, often twisting two or three times. They turn brown upon maturity and house several small, kidney-shaped seeds.
Growth Habit and Environmental Preferences
As a perennial, alfalfa regrows each season from its crown, allowing it to maintain fields for several years. The plant is supported by an extensive and deep taproot system. This singular, thick root can penetrate the soil to depths exceeding 20 feet, providing exceptional resistance to drought by accessing deep moisture. The taproot also stores carbohydrates used to fuel regrowth after cutting and ensure winter survival.
Alfalfa grows best in areas that receive full sun. It requires deep, well-drained soil; standing water or poorly draining soils can promote diseases. The soil should be near neutral in pH, with a range between 6.5 and 7.0 being ideal. This pH range supports symbiotic bacteria in the root nodules, which convert atmospheric nitrogen into a usable form for the plant.
Identifying Alfalfa Versus Common Field Plants
The common search term “alfalfa grass” highlights the frequent confusion between this legume and true grasses or clover. True grasses have narrow, parallel-veined leaves and inconspicuous flowers, contrasting sharply with alfalfa’s broad, trifoliate leaves and showy purple blossoms. Alfalfa lacks the narrow, hollow stems and fibrous root systems characteristic of grasses.
Distinguishing alfalfa from clover requires a closer look at the leaf structure. While both plants have three leaflets, alfalfa’s central leaflet is set on a slightly longer stalk (petiole) than the two side leaflets. Many common clovers, such as white clover, often have a distinct V-shaped watermark on the surface of each leaflet. Alfalfa leaves typically lack this marking, presenting a more uniform color. When fully mature, alfalfa grows significantly taller than many clovers, often reaching three feet, while clover remains low to the ground.