Alfalfa (Medicago sativa) is a perennial legume highly valued globally as the most important forage crop. Primarily cultivated for hay and silage production, its nutrient-rich profile makes it a staple feed source for high-producing livestock, particularly dairy cattle. The plant’s ability to fix atmospheric nitrogen and its deep root system make it a significant component of sustainable agricultural systems. Understanding the typical size it reaches is central to effective cultivation and harvest management.
Typical Height Range and Maximum Potential
Under normal agricultural cultivation, alfalfa typically reaches a mature height between 2 and 3.5 feet (60 to 107 centimeters). This height represents the standing crop just before harvest. The plants grow upright, developing multiple stems from a crown near the soil surface.
The maximum potential height for alfalfa can sometimes exceed 4 feet (122 cm) if allowed to grow indefinitely. This maximum height is rarely seen in commercial fields because the plant is cut for hay long before reaching its full botanical potential. Growers often target 28 to 30 inches (71 to 76 cm) during the first cutting to balance biomass yield with nutritional quality. The height achieved is a direct result of environmental conditions and management decisions.
Environmental Factors Driving Alfalfa Growth
The specific height alfalfa achieves is highly dependent on environmental variables, with soil health being a primary factor. The plant develops an extensive taproot system that can penetrate the soil 4 to 5 feet, sometimes reaching over 15 feet in search of water and nutrients. This deep rooting requires well-drained, fertile soil, and alfalfa thrives best in a surface pH range of 6.5 to 7.0. Poor soil conditions or low pH inhibit root development, directly limiting the plant’s ability to grow tall.
Water availability is another regulating factor, as drought conditions severely stunt vertical growth. Inadequate rainfall forces the plant to mature at a shorter height because the lack of soil water limits cell expansion and biomass accumulation. Temperature and sunlight also influence the rate of growth and final height. With adequate moisture, alfalfa grows taller in cooler environments compared to warmer ones before flowering, which is why the first cutting is often the tallest. Sufficient solar radiation drives the photosynthesis needed for rapid vertical stem elongation.
Height in Relation to Cutting Schedules
In commercial production, alfalfa height serves as a practical indicator for determining the optimal time for harvest. The plant is rarely allowed to reach its maximum potential because its nutritional quality declines as it matures and grows taller. Taller alfalfa plants, even at the same maturity stage, contain a lower Relative Feed Value (RFV) due to a higher proportion of fibrous stem material relative to leaves.
Consequently, growers manage height to balance maximizing forage yield (which increases with height) and maintaining high digestibility and protein content. For a high-quality product, the first cutting of the season might be harvested when it reaches 28 inches. Later, warmer-season cuttings may be shorter, sometimes only 21 inches, at the equivalent stage of maturity. The frequency of these cutting events throughout the season affects the average height observed in the field. Shorter, more frequent cutting cycles result in consistently lower-statured plants across the growing season.