The aggressive nature of weeds and their prolific reproductive capacity enable them to invade thin, weak turf areas. Cultural practices should always be viewed as the first step to effective weed control. Always determine why weeds established a foothold and correct those deficiencies. If the basic problem is not corrected, weeds will continue to occur. An effective weed control program also requires identification of the undesirable species as to its classification as a grassy weed, a broadleaf weed, an annual or a perennial.
Most turf weeds belong to two principal categories - grasses and broadleaf plants.
Chemical controls for these two categories of plants frequently differ. Another group of turf weeds, sedges, have grass-like characteristics, but require a different group of chemicals for control. Weeds can be further grouped according to their life span - annual or perennial. From the standpoint of chemical control, the grouping is most important because preemerge herbicides are only effective for control of annual weeds. Crabgrass and henbit are examples of annual weeds - crabgrass being a summer annual and henbit being a winter annual.