Crown vetch (Coronilla varia) is a perennial legume valued for its ability to create a dense, low-maintenance groundcover. Its aggressive spreading habit and robust root system make it effective for stabilizing slopes, controlling erosion, and enriching soil through nitrogen fixation.
Preparing Crown Vetch Seeds
Crown vetch seeds have a hard outer coat that inhibits germination. Scarification is necessary to break down this coat, allowing water absorption. Mechanical scarification involves physically abrading the seed, such as by rubbing it with sandpaper or carefully nicking it with a knife.
Another method is hot water scarification, where seeds are soaked in hot, but not boiling, water. Pouring hot water over the seeds and allowing them to cool and soak for 12 to 24 hours can soften the seed coat. After treatment, seeds that have swollen indicate successful scarification and are ready for planting.
Beyond scarification, inoculating crown vetch seeds with a specific Rhizobium inoculant is beneficial. This introduces bacteria that enable nitrogen fixation, enriching the soil and promoting healthier plant growth, reducing the need for external nitrogen fertilizers. To apply the inoculant, moisten the scarified seeds with a small amount of water, or a sticking agent like a sugar solution, then thoroughly mix them with the powdered inoculant until each seed is coated. Plant these inoculated seeds within 24 hours to ensure the bacteria remain viable.
Site Selection and Soil Preparation
Crown vetch thrives in full sun but can tolerate partial shade, though flowering may be more abundant in sunnier conditions. Crown vetch adapts to a wide range of soil types, including low-fertility sites and those with a pH between 5.0 and 7.5, but it performs best in well-drained soil. Proper drainage is important, as soggy conditions can lead to root rot.
Preparing the soil involves clearing the planting area of existing weeds and debris. This step helps to reduce competition for the young crown vetch seedlings. While crown vetch tolerates poor soils, light tilling or raking the surface creates a loose seedbed that facilitates better seed-to-soil contact. If the soil pH is below 5.5, applying lime can help raise it to a more favorable range.
Planting Crown Vetch Seeds
Early spring, after the last frost, is generally suitable for planting crown vetch seeds. Alternatively, seeds can be sown in late fall, allowing them to remain dormant over winter and germinate in the spring through a process known as frost seeding. For fall planting, it is advisable to plant at least 10 weeks before the first hard frost to allow for some establishment.
Broadcast the prepared seeds evenly over the surface of the tilled soil. For general groundcover, a seeding rate of about 1 pound per 1,000 square feet is recommended. For erosion control, a slightly higher rate of 5 to 15 pounds per acre can be used. After broadcasting, lightly rake the seeds into the soil, aiming for a shallow depth of approximately 1/8 to 1/4 inch. Ensuring good seed-to-soil contact is important for germination.
After sowing, gently water the newly planted area. Use a fine spray to avoid washing away the seeds or disturbing the shallowly planted bed. This initial watering helps settle the seeds into the soil and provides the moisture needed for germination. Maintaining consistent moisture is important during this early phase.
Initial Care for Crown Vetch Seedlings
Consistent moisture is important for crown vetch germination and seedling establishment. The seedbed should be kept moist but not waterlogged through regular, light watering. Once the seedlings emerge and begin to establish a root system, the frequency of watering can be reduced.
Control weeds during the early growth of crown vetch. Weeds can outcompete young crown vetch seedlings for light, water, and nutrients. Hand-pulling weeds around the emerging plants can help minimize competition without disturbing the delicate seedlings.
Crown vetch germination typically ranges from 3 to 5 weeks. Monitoring the planted area for signs of germination and initial growth is helpful. Although crown vetch can be slow to establish from seed, its aggressive growth once mature helps it form a robust groundcover.