Weeds are described as plants growing where they are not wanted. They can disrupt the appearance and use of lawns, recreational areas, and other turfs. In addition, they compete with desired turfgrasses for space, water, nutrients, and light. Turf weeds may be grasses, grass-like plants (rushes and sedges), or broadleaf plants with annual, biennial, and/or perennial life cycles.
Turf professionals should become familiar with weed characteristics, growth habits, and life cycles. These factors play an important role in weed identification and control. A weed management program is based upon identifying the desired turfgrasses and existing weeds, including knowledge of other weeds that may potentially germinate. However, an effective program begins with a vigorous turf; one that has been correctly fertilized, watered, and mowed. Weeds can quickly invade thin turf. Cultural and management practices that enhance turfgrass growth generally reduce weed competition and encroachment. When selecting a herbicide, consider the weeds present, those that will potentially germinate, and the tolerance of the turfgrass.
Selection of adapted turfgrass species and cultivars and the use of cultural practices are important in minimizing weed encroachment and competition. Management practices include:
(1) mowing at the recommended height for the selected turfgrass species and removing clippings when seedheads of grassy weeds are present
(2) applying the proper amount of nitrogen at the correct time according to the turfgrass present;
(3) using soil tests to determine needed nutrients and lime; and
(4) properly identifying the weed species, then applying appropriate herbicides either before weeds germinate (preemergence) or when weeds are small and actively growing (postemergence).
From the extremely helpful resource: Turf Files, NCSU: