Crimson clover (Trifolium incarnatum) is a popular cool-season annual known for its rapid growth, ability to fix nitrogen, and distinctive scarlet-red flowers. Often used as a cover crop or high-quality forage, this plant is valued for its contribution to soil health and livestock feed. A frequent question among those considering its use is whether this plant can reliably return year after year without being replanted. The answer is yes, crimson clover has a strong natural ability to regenerate itself, a trait that is highly dependent on both its internal biology and external environmental factors.
The Annual Cycle and Reseeding Capability
Crimson clover is classified as a winter annual. It germinates in the fall, grows through winter, matures in the spring, sets seed, and dies by early summer. Since the individual plant does not survive multiple seasons, producing new seed is its only mechanism for returning the following year. This regeneration relies on a biological strategy called “hard seed” production, which is the key to its self-reseeding potential.
Hard seed refers to seeds with a water-impermeable seed coat that prevents immediate germination, even when conditions are favorable. The percentage of hard seed can vary significantly among varieties, often ranging from 30% to 75%, creating a “seed bank” in the soil. This dormancy ensures that only a portion of the fallen seed germinates right away, while the rest remains viable through the hot, dry summer months. The hard seed coat slowly breaks down over time through natural weathering, allowing the seed to become permeable and germinate once the cool, moist conditions of the following fall return.
Optimizing Conditions for Natural Reseeding
Successful natural reseeding of crimson clover is not guaranteed and requires careful management to ensure a sufficient number of seeds are produced and successfully establish. The first step involves allowing the clover to complete its reproductive cycle, which means permitting the spring growth to flower fully and mature seed. Flowering is typically triggered when day length exceeds 12 hours, and seeds generally mature within about 30 days of pollination. Premature mowing or grazing during this period can prevent the necessary seed drop, eliminating the next generation’s stand.
After the seeds have matured and dropped, ensuring good seed-to-soil contact is the next factor influencing the success of the volunteer crop. Light disturbance, such as minor disking or the action of livestock hooves, can help press the seeds into the soil surface, protecting them from drying out or being washed away. Crimson clover seeds should ideally be covered with no more than a quarter-inch of soil, as deeper burial can prevent successful emergence. The final requirement is sufficient moisture during the late summer and fall to facilitate the germination of the now-softened seeds. While the hard seed trait protects against premature germination during summer, the new seedlings are highly dependent on adequate soil moisture in the fall to establish before the first frost.
Managing Reseeding for Different Uses
The management strategy for reseeding must be tailored to the clover’s specific use, as maximizing forage yield often conflicts with maximizing seed production. For hay or grazing, the goal is high biomass, encouraging early cutting or heavy grazing before the plant sets seed. To manage a field for reseeding, livestock must be removed or grazing pressure reduced when the clover begins to bloom (late March or early April), allowing the plant to allocate energy toward seed development. Once the seed heads are dry and the seeds are mature, grazing can resume, as livestock can help press the fallen seeds into the soil.
For its role as a self-sustaining cover crop, especially in no-till systems or perennial orchards, the reseeding ability is a significant cost-saving advantage. Farmers can allow the clover to set seed in the late spring, and the resulting volunteer crop will germinate in the fall. This provides season-long erosion control and nitrogen fixation without the annual cost of seeding. Conversely, if reseeding is not desired in a rotation, the plant must be terminated before the seeds mature, typically by mowing at the early bud stage or using herbicides. Using soft-seeded varieties, which lack the long-term dormancy of hard seed types, also helps prevent unwanted reseeding in subsequent cash crops.