White clover (Trifolium repens L.) is a perennial that is commonly used in lawns and as a pasture feed. The plant enjoys moist, cool growing conditions in soil that is well-draining. White clover spreads from stolons and its root system is quite shallow so it cannot withstand drought conditions. In order for seed production of white clover to be successful the the plant must be forced to produce less foliage and more stolons.
Stolon Production and Grazing
Producers of white clover seeds will plant the clover plants in rows that are a minimum of 20 inches wide to allow the stolons to readily form. Seed production is believed to be increased when white clover is grown in full sunlight. The top growth of the white clover is subjected to heavy grazing by sheep to place the plant into a state of perpetual stress. Grazing should take place after the fall harvest and for a month in the early spring.
Every growing year is different with white clover. For a few years the plants will often flourish despite heavy grazing and the seed production is poor. On years where the plant exhibits abundant stress from heavy grazing it begins to form abundant stolons and the seed harvest in August is excellent. The stress that the plant suffers greatly influences the seed production rates. The more stress, the more seeds.
Seed producers regularly rotate white clover every two to four years to maximize seed yields. A few growers have been experimenting with using herbicides to make the clover stands last longer. They apply it using a shrouded sprayer that has a unique design with coulters along the sides close to the spray nozzles. The coulters (large blade cutting instruments affixed to a disk) cut through stolons and help prevent the rows of white clover from uptaking the herbicide to protect the clover plants according to the Oregon Clover Seed Industry.
Seed production of white clover is difficult because weeds need to be kept at bay in order that the weed seeds do not become mixed with the clover seeds. Herbicides are commonly used but most seed farm producers utilize hand weeding to maintain control of the fields.
Pollination For Seed Production
Bees are the best pollinators for white clover when heavy seed production is desired. White clover is commonly considered to be self fertile but fertility is drastically increased when bees are utilized in the fields.