Alfalfa (Medicago sativa) is a perennial legume crop prized for its high protein content and use as livestock forage, hay, and silage. The deep-rooted plant can remain productive for several years under good management. Determining how long alfalfa takes to grow is complex because its timeline shifts significantly based on the plant’s stage of development and local environmental conditions. The growth rate changes dramatically between the initial establishment phase and the subsequent, regular harvest cycles.
Establishing the Stand: Time to First Harvest
The time from planting to the first major harvest is a distinct, lengthy period focused on developing a healthy, persistent root system rather than maximizing initial yield. This initial growth phase typically requires 60 to 90 days following seedling emergence, though it can extend up to 120 days depending on the planting season and climate. Planting in the early spring often allows for a faster initial growth rate than late summer or fall planting.
The main objective before the first cut is ensuring the seedling develops a deep taproot and a strong crown. Cutting the crop too early depletes limited carbohydrate reserves, weakening the stand and reducing its longevity. For optimal stand health, managers wait until the plants are at the late bud to early bloom stage. This practice ensures enough energy is stored in the roots to support vigorous regrowth and winter survival.
The Cutting Cycle: Regrowth and Subsequent Harvests
Once the alfalfa stand is well-established, the subsequent cutting cycle is significantly shorter, focusing on maximizing forage quality and yield. Established stands typically reach harvest maturity faster, usually within a 28 to 40-day interval. The speed of regrowth is less about calendar days and more about the accumulation of heat, quantified using Growing Degree Days (GDD).
Using Growing Degree Days
The GDD model uses a base temperature to calculate the daily heat available for plant growth, providing a more accurate prediction of maturity than a fixed time frame. Faster accumulation of heat units in mid-summer leads to quicker regrowth and shorter intervals between cuts. Cooler spring and fall periods slow the process considerably.
Stubble Management and Winter Dormancy
Proper management of the stubble height is important for fast regrowth, as leaving adequate height ensures new shoots from the crown are protected. This also provides the plant with sufficient photosynthetic material to quickly restart energy production. A final consideration is the timing of the last cut before winter dormancy. This cut must either allow for six weeks of regrowth to replenish root reserves or occur so late that the plant does not deplete its stored energy on futile regrowth.
Environmental and Management Factors Influencing Growth Rate
The timelines for both stand establishment and subsequent cutting cycles are highly sensitive to external variables, which can either accelerate or severely stunt the alfalfa’s growth. Temperature plays a dominant role, with optimal growth occurring when daytime temperatures are in the range of 68° to 85°F. Growth slows significantly below 41°F, and prolonged periods above 90°F can limit growth and reduce the nutritional quality of the forage.
Soil and Water Requirements
Soil conditions are a major determinant of growth speed. Alfalfa requires a well-drained soil structure to prevent root disease and a neutral pH, ideally between 6.5 and 7.5, for efficient nutrient uptake. The availability of water is the most immediate factor influencing the cutting cycle, as alfalfa has a high water requirement due to its fast growth rate. Drought conditions severely limit the plant’s ability to regrow, forcing longer intervals between harvests, while irrigation can maintain a consistent, faster cutting schedule.
Pests and Diseases
The presence of pests and diseases, such as the alfalfa weevil or various root rots, can damage foliage and roots. This forces the plant to divert energy toward recovery, thus delaying the time it takes to reach harvest maturity.