For example, creeping bentgrass plants can invade a Kentucky bluegrass lawn and cause unsightly patches. On a golf green, however, creeping bentgrass is highly desirable as the predominant plant. Weeds detract from the beauty of lawns due to the contrast in color and texture between the desired grass plants and the weeds. In addition, weeds compete with the desired grass plants for available water and nutrients, usually resulting in thinning of desirable plant cover. Identification and Characteristics Lawn weeds may conveniently be divided into two classes based on the way in which they emerge from the seed.
Monocots emerge with a single seed leaf whereas dicots emerge with two seed leaves.
Most monocot weeds found in turfgrass are from the family Gramineae and are termed weedy grasses . Examples include crabgrass, annual bluegrass, tall fescue, and quackgrass. Dicots, on the other hand, are termed broadleaf weeds and include such plants as dandelion, clover, ground ivy, knotweed, and plantain. Weedy grasses and broadleaf weeds are further divided into groups according to the plants' length of life. Perennial weeds have a life of more than two years, though new seeds may be produced every year.