Red clover (Trifolium pratense) is a short-lived perennial that is hardy in U.S. Department of Agriculture plant hardiness zones 5 through 9. It can potentially return year after year in those zones, but it often dies on its own in its second growing season, causing it to perform like a biennial.
The plant has compound leaves, each made up of three oval-shaped leaflets, and it grows to a height of about 2 feet. It produces flower heads made up of many flowers, each about 1/2 inch long and pink-purple or white in color.
Red clover grows best when planted in areas with moist but well-drained soil. It is able to grow in most soil types, including sandy, loam and clay soils, and it does well in nutrient-deficient soils. It prefers full sun and does not grow well when planted in shady locations.
Red clover is a legume, which means that is able to contribute nitrogen to the soil as it grows, and that nitrogen can be used by other plants that are subsequently grown in the same place that red clover was grown. To take advantage of that benefit, gardeners can grow red clover as a cover crop, sowing its seeds in the garden in early spring then till the clover into the soil later in spring before planting vegetables or ornamentals.
Besides their contribution of nitrogen, cover crops also help to prevent erosion, loosen garden soil and increase the soil's organic content when they're tilled into the ground. To encourage clover to die back in spring, mow it close to the ground before it flowers, and then till it under the soil surface.
The young leaves and flowers of red clover are edible and are sometimes used in salads or cooked like spinach (Spinacia oleracea). The plant's sprouted seeds also are used in salads, and its leaves are dried and used as herbal flavoring in baked goods and as an infusion in tea. According to Plants for a Future, use caution when harvesting clover for ingesting because diseased plants, even those that show no symptoms can contain toxic alkaloids.
Weediness and Invasiveness
If allowed to grow too long in spring when planted as a cover crop, red clover can become problematic because it pulls nitrogen and moisture from the soil, resulting in unfavorable growing conditions for subsequent crops.
Red clover also sometimes invades lawn turf, where it competes for resources with turf grasses. Proper maintenance of the turf, including watering adequately and mowing the turf grass to its appropriate height, can reduce the chance that red clover becomes established in the lawn.