Alfalfa, also known as lucerne, is a globally recognized forage crop used extensively for hay and silage due to its high protein and mineral content. While the plant is biologically capable of producing viable seeds, reliable self-reseeding rarely sustains a productive stand under typical agricultural cultivation. This perennial plant is managed for its foliage, meaning the biological cycle that would lead to reseeding is intentionally interrupted by routine harvesting practices.
Understanding Alfalfa Stand Longevity
Alfalfa is classified as a perennial plant, meaning its survival over multiple seasons is not dependent on annual seed production. The plant’s long-term persistence is rooted in its specialized subterranean structures: the taproot and the crown. The crown is a compressed stem structure located just below or at the soil surface, from which new shoots emerge each spring and after each harvest.
The plant develops a deep, extensive taproot system that can penetrate the soil to depths of 15 to 20 feet or more. This deep root allows the plant to access soil moisture and nutrients unavailable to shallower-rooted crops, providing resilience against drought. The taproot also serves as a storage organ, accumulating large reserves of carbohydrates used to fuel winter survival and vigorous regrowth after dormancy or cutting.
This mechanism of survival and regrowth from the established crown maintains a productive alfalfa stand for multiple years, often six years or longer under ideal management. When the plant is harvested, the energy stored in the taproot is mobilized to produce new shoots from the crown buds. Factors that reduce these carbohydrate reserves, such as untimely or frequent harvesting, weaken the crown and shorten the stand’s lifespan.
The Biological Potential for Natural Reseeding
Despite being maintained as a perennial, alfalfa is a flowering plant that produces fruit in the form of spiraled seed pods, each containing 10 to 20 seeds. If a stand is allowed to complete its reproductive cycle without being harvested, it can produce a large number of viable seeds. Successful natural reseeding requires delaying harvest until the seed pods are fully mature and ripe, typically around the Stage 9: Ripe Seedpod stage.
Once on the soil, the seeds face “hard seed” dormancy, where the seed coat is impermeable to water. This natural defense mechanism prevents all seeds from germinating at once and requires scarification—such as physical abrasion or freeze-thaw cycles—to break the tough outer coat. Adequate soil moisture and a soil temperature above 40°F are necessary for the newly scarified seeds to germinate.
Natural reseeding can be observed in unmanaged areas or along field edges where plants are permitted to flower and drop their seeds. However, the resulting stand is often patchy and unevenly distributed. This biological potential demonstrates the plant’s ability to propagate itself, but it rarely translates into a reliable method for commercial field maintenance.
Factors Preventing Reliable Self-Seeding in Cultivation
Commercial agricultural practices are designed to maximize forage quality and yield, which directly interferes with the plant’s ability to produce mature seeds. Alfalfa is typically harvested at the bud stage or early bloom stage, well before the plant has developed or ripened any seeds. This early, frequent cutting eliminates the seed source, preventing significant self-reseeding across the field.
Another significant obstacle is autotoxicity, where established alfalfa plants release chemical compounds into the soil that inhibit the germination and growth of new alfalfa seedlings. This chemical self-defense is potent in established stands that are two years old or older, making it difficult for new alfalfa plants to survive even if a seed successfully germinates. For this reason, farmers are advised against overseeding an existing alfalfa stand with more alfalfa.
Furthermore, natural reseeding rarely achieves the uniform stand density required for profitable hay production, which is typically established with a high initial density aiming for 25 to 35 plants per square foot. As the stand ages and plant populations decline, open areas are quickly invaded by weeds that outcompete new alfalfa seedlings. Therefore, when a stand’s productivity declines, rotating to a different crop before replanting alfalfa is the standard management strategy.