Text Box: Sweet Clover is a European native that was brought to the United States in the 1600’s as a forage crop. Today, it invades and degrades Iowa’s grasslands by shading out native plants and reducing diversity. Sweet clover is a sweet-smelling biennial legume (in the pea or bean family), with green clover-leaves and white or yellow flowers. Second-year plants grow 3 to 5 feet high and are wide and bushy. The flowers bloom in June through August, and each flower produces one or two small, hard seeds. These seeds can remain viable in the soil for thirty years or more. Sweet clover is typically found in open areas; fields, roadsides, upland prairies and savannas. To control this persistent invasive, an integrated approach of depleting the existing seed bank and preventing seed production is required. The best management requires a combination of burning, pulling, and spraying. Prescribed burning for two consecutive years or more can help to reduce populations. Burns should be held in late-fall or early-spring the first year and late-spring the second year. Initially, burning will stimulate the seed bank, and must be used in conjunction with pulling, mowing, or spraying. This will prevent new plants from setting seed, eventually exhausting the seed bank and reducing Text Box: the population. Pulling plants is most effective if second-year plants are pulled in late spring (May) before they set seed. The complete plant, including the root must be pulled to avoid re-sprouting. Herbicide can be very effective at controlling sweet clover. Effective herbicides include glyphosate (e.g. Round-up, Glyphos X-tra, etc.) or 2, 4-D; although these herbicides are not species-specific and will harm adjacent vegetation. Clopyralid (e.g. Transline) is specific to legumes (such as sweet clover), asters, nightshades, and smartweeds and will not kill grasses. Spraying is especially effective if done in the spring, following a fall burn. Mowing can be effective if done in mid to late August, followed by a burn in mid to late September. Mowing repeatedly in late spring/ early summer will also help to reduce seed production but will not eradicate the population. Monitoring your property for new populations of sweet clover is essential, as much less time and money is required to control a patch that does not have an extensively established seed bank. Seeds are easily tracked by people, turkey, deer, and other wildlife and are easily transferred on the tires of mowers, tractors, and other equipment.

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Text Box: Sweet Clover Control

 Loess Hills Conservation