Clover crops up when fertility is low

White clover indicates low soil fertility. Black medic, a weed with leaves similar to clover, sports yellow flowers in the foreground. © Jo Ellen Meyers Sharp

Driving around town it’s hard not to miss what seems to be a bumper crop of clover. Seemingly overnight, white balls of flowers have popped up in patches or spread throughout the lawn.

Back in the days when all we wanted was a lawn that was green, clover (Trifolium repens) was part of the grass seed mix. A member of the pea family, it originated in Europe and is the most widely distributed legume in the world, according to the U.S. Department of Agriculture Natural Resources Conservation Service.

A low-growing perennial, clover spreads by stolons, or stems, which creep slightly below the soil surface. Legumes are important because they fix, or hold, nitrogen, which moves quickly through the soil, especially with a lot of rain. Clover also is nutritious forage for cattle and wildlife. Pollinating insects, such as bees, favor it, as do deer.

As lawn-weed killers became more widely available in the 1950s and 1960s and pressure for suburban weed-free lawns grew, clover landed on the undesirable list with dandelions and crabgrass.

Clover appears in lawns where the soil is low in nitrogen. The remedy is to apply a nitrogen fertilizer, according to label directions. Fall aeration also will help beef up the soil with nutrients to help fend off the clover.

For more information, check out Purdue University’s Plant & Pest Diagnostic Laboratory’s publication on white clover.

Red clover. Photo courtesy National Park Service.

Red clover (Trifolium pratense) is another perennial that comes from Europe, Asia and Africa. It is much larger than white clover and has a pink flower. It, too, has naturalized throughout the country, is a forage plant for cattle and wildlife, and a nectar plant for insects.

There are two invasive weedy perennials that resemble clovers. Black medic (Medicago lupulina), has clover like leaves, but produces a yellow flower ball.

Sorrel (Oxalis), also has clover like leaves, but a yellow star flower. Some oxalis species are grown as ornamental plants in pots for summer.

Wood sorrel. Photo courtesy University of Arkansas