Clovers originated in southeastern Europe and southwestern Asia Minor. They were once believed to be a curative for heart disease because of their heart-shaped leaves. Modern medicine has extracted a chemical, coumarin, from clover which is used as a blood thinner.

White or Dutch clover (Trifolium repens) has three-part green, heart-shaped leaves with white crescents and pink or white flowers. It grows about 6"-8" high. It is a perennial plant that tolerates dry soils but thrives during wet, cool summers. Clover is more competitive in fertile, poorly drained soils, due to its ability to make use of atmospheric nitrogen. It has a shallow root system and spreads by runners. It also grows from seed.

Until the 1950s, clover was included in lawn seed mixes as it was regarded as a prestigious lawn plant. It may be considered an attractive, low-maintenance ground cover that is soft to walk on, mows well and will fill in thin spots in a yard. Or it may be considered a weed which does not readily withstand heavy foot traffic.

Clover can become invasive in thin lawns. Its flowers attract bees which may sting children playing in it. Clover will easily stain children's clothing. Its flowers become unattractive when they turn brown so the plant looks best when mowed frequently.

Planting Clover
Clover does best when planted in spring and summer. If you wish to add clover to your lawn, power rake or otherwise scruff the soil surface to provide good soil to seed contact. Seed at a rate of 2 to 8 oz. per 1,000 square feet, depending on the amount of clover desired in the lawn. At 8 oz. per 1,000 square feet, clover will become the dominant plant.

Since clover seeds are small, uniform distribution may be difficult. Mix sawdust or Milorganite, a low analysis organic fertilizer, with the seed prior to spreading to simplify distribution. Keep soil moist until clover has become established. Clover will not thrive under a program of heavy fertilization.

White clover is not reliably hardy in Minnesota. Plant populations fluctuate depending on the severity of the winter. If the clover stand is thin one year, it usually recovers in following years, so over-seeding should not be necessary.

Controlling Clover
If you consider clover a weed, and want to control it, spray with MCPP in spring or fall, when temperatures are expected to remain cool. Do not use it when temperatures are predicted to reach 80 to 85 degrees within 24 hours. MCPP, (short for 2-(2-methyl-4-chlorophenoxy) propionic acid), may be listed as mecoprop and is the active ingredient in clover and chickweed killer. It is also found in some general purpose broad-leaf weed killers. Wait 3 to 4 weeks before reseeding after using MCPP. Don't reapply MCPP if clover appears unaffected. Usually it takes 6 to 8 weeks for the clover to disappear.

Clover is invasive only when conditions exist that are unfavorable for grass growth, such as low soil fertility, compaction and poor soil aeration. Maintaining healthy grass keeps clover from spreading aggressively.

To improve your lawn, water the grass thoroughly every week to week and a half to encourage deep roots. Rainfall and irrigation should equal an inch per week. Frequent light watering encourages clover, which is shallow-rooted. Mowing your lawn no shorter than 2½ to 3 inches also encourages deeper grass roots.

Aerate lawns in early fall to promote better drainage in heavy, compact soils. Have your soil tested to determine soil fertility and fertilize accordingly.

The other clover commonly found in Minnesota is red clover (Trifolium pratense). It tolerates acidic or poorly drained soil, and is commonly used as a forage crop for animals. It grows best in unmowed, unmaintained sites where it reaches a height of 14"-18". Red clover is not suitable as a groundcover because it is a biennial, meaning it lives for only two years. It is unsuitable for lawns because it has coarse stems which look awful when they're mowed. It also attracts bees which may be unwanted in a home yard.