Weeds are the undesired plants in lawns that damage grass by competing for nutrients, water and space. Lawns infested with weeds grow less vigorously and gradually start to thin. Weeds often are easily identifiable by distinct features such as those with yellow flowers.
Yellow lawn weeds include birdsfoot trefoil (Lotus corniculatus), creeping woodsorrel (Oxalis corniculata) and dandelion.
Birdsfoot trefoil is a perennial broadleaved that often grows alongside black medic and white clover. The plant produces large, yellow flowers in late June. Creeping woodsorrel has reddish purple, heart-shaped foliage with contrasting yellow flowers. Dandelion has deep taproots with lobed foliage and bright yellow flowers on leafless stems. The plant produces puffy, globular seed heads that are dispersed by mowing and wind.
Dandelion is the most common lawn weed, according to the Michigan State University Extension. The plant adapts to a range of soil and growing conditions. Birdsfoot trefoil is more common in warm, under fertilised soil and generally sprouts along sidewalks and curbs. Creeping woodsorrel is highly invasive and grows in all soil types. Established plants are very hard to control.