Alfalfa seeds, derived from the flowering legume Medicago sativa, are used for sprouting as a nutritious food source or for planting as a high-protein forage crop, cover crop, or green manure. Seeds can be obtained through two primary methods: purchasing from commercial vendors or harvesting them directly from an established alfalfa stand. Both avenues require attention to detail to ensure the seeds are of the appropriate quality for the intended use.
Commercial Sources for Alfalfa Seeds
Purchasing alfalfa seeds requires careful consideration of the seed’s grade, which directly relates to its quality and intended purpose. Specialty seed companies, local farm supply stores, and feed stores are the most common vendors, while online specialty seed suppliers typically offer a wider range of certified varieties suitable for planting.
A major distinction exists between planting-grade and feed-grade alfalfa seeds, primarily concerning purity and germination standards. Planting-grade seed must meet stringent requirements, often labeled as “Certified” or “Proprietary Variety.” This certification ensures the seed’s genetic identity, a high percentage of purity, and minimal contamination from noxious weed seeds.
Feed-grade seeds are intended for animal consumption and are unsuitable for establishing a new crop stand due to lack of purity or germination guarantees. When purchasing for planting, examining the seed tag is paramount, as it details the percentage of pure seed, germination rate, and the presence of any weed or other crop seeds. The Pure Live Seed (PLS) calculation accounts for both purity and germination, providing the true measure of viable seed in the bag.
Harvesting Alfalfa Seeds from Your Own Crop
Producing alfalfa seeds from an existing crop stand requires specific timing and management that differs significantly from harvesting for hay. Instead of cutting the plants at the early bloom stage for forage, the alfalfa must be allowed to fully mature to allow for seed set. Seed production often occurs on the second or third cutting of the season, when conditions are typically drier and more favorable for pollination.
The appropriate harvest time is determined by the maturity of the seed pods. Pods start as green coils but must be fully dry and dark brown or black before cutting. Harvesting too early results in shrunken, immature seeds, while waiting too long can lead to shattering and significant seed loss in the field. After cutting, the plants are left to cure, or dry further, in the field to ensure the seed moisture content is low enough for proper threshing and storage.
For small-scale harvesting, the process involves three distinct steps: threshing, separating, and cleaning. Threshing involves physically breaking the dried pods to release the small, kidney-shaped seeds, which can be done manually by beating the dried material against a surface or by walking over it on a tarp. Winnowing is the traditional method of cleaning, where the mixture is tossed into the air, allowing a gentle breeze to carry away the lighter debris (chaff) while the heavier seeds fall back down.
Post-Acquisition Handling and Storage
Once the alfalfa seeds are acquired, whether purchased or harvested, proper handling is necessary to maximize their viability and ensure successful planting. Two key preparation steps for planting are scarification and inoculation. Alfalfa seeds are characterized by a hard seed coat, which can be impermeable to water, leading to a condition known as “hard seed” that prevents immediate germination.
Scarification is the process of physically or chemically breaking this hard outer layer to allow moisture uptake and initiate germination. Commercially purchased seeds are often mechanically scarified, but if a high percentage of hard seed remains, a home grower may use abrasive methods, such as lightly rubbing the seeds with sandpaper.
The second preparation step is inoculation, which involves coating the seeds with a specific strain of Rhizobium bacteria, typically Sinorhizobium meliloti. These bacteria form nodules on the alfalfa roots, allowing the plant to fix atmospheric nitrogen into a usable form, thus eliminating the need for nitrogen fertilizer.
While many commercial seeds come pre-inoculated, the bacteria can lose viability over time or with improper storage. Applying fresh inoculant just before planting is a recommended safeguard, especially for carryover seed.
For long-term preservation of any seed, storage conditions should prioritize low humidity and cool, stable temperatures, ideally below 50°F. Storing seeds in airtight containers in a cool, dark environment helps maintain their viability for several years, slowing the natural decline in germination rate over time.