A dense stand of healthy grass provides the best weed control. All cultural practices such as mowing, fertilizing and watering should be done in a manner and time that will favor the grass rather than the weeds. Height of mowing influences competition against weeds such as crabgrass - the higher the cut, the lower the infestation. Frequent light sprinkling encourages shallow-rooted weeds and seed germination. Temperature, light, soil moisture and other factors determine the time and extent of weed germination and development.
Some weeds germinate in early spring while others sprout in summer or fall.
If conditions are favorable, a weed may be particularly abundant in a given year, but under different conditions the next year, it may be little in evidence. Although most herbicides are formulated with reliable safety factors, application rates higher than those recommended may cause injury to turf and other ornamental plants. Many people over apply herbicides, especially when using fertilizer-herbicide combinations. The user needs to follow instructions on containers carefully to avoid overdoses. Apply two to four weeks ahead of germination.