Lawns require lots of water and fertilizer in addition to lots of sun, in order for them to grow thick and lush. Unfortunately, lawn weeds also grow thick and lush in well-watered and well-fertilized lawns. The best way to get rid of lawn weeds is to grow healthy grass--the grass will eventually crowd out the weeds. Spend a growing season or two consciously attacking your lawn weeds and chances are very good that they will be eradicated.
Change the frequency with which you mow your lawn. Mow lawns that have a lot of weeds more often to reduce the leaf surface area of weeds and prevent them from producing flowers and going to seed. Cool-season grasses will require more frequent mowing during cool weather and less frequent mowing during warm weather. Conversely, warm-season grasses require more frequent mowing during warm weather and less frequent mowing during cool weather.
Change the frequency of watering--more often or less frequent. Generally speaking, warm-season grasses need a thorough watering only once per week during times when they are in active growth. Cool-season grasses need to be watered two or even three times per week during their active growth period. Areas is shade need less watering than lawns in sunny areas. Clay soil will retain water more readily than sandy soils and consequently will need less frequent watering.
Apply pre-emergent herbicide in early spring to kill seeds of annual weeds before they germinate. Apply post-emergent herbicide in mid-spring to kill broad-leaf, perennial weeds after they emerge from their roots. These types of herbicides are most often applied in granulated form using either a hand spreader or a drop spreader. A drop spreader is pushed in front of the operator across the lawn, first in one direction and then in another. A hand spreader is held at waist height and a crank is turned, which distributes the herbicide through holes in the bottom. Place the herbicide in the spreader, following the herbicide manufacturer's recommended rates of application. Follow the operating instructions of the manufacturer of the hand or drop spreader for best results.
Hand-pull weeds as they develop. Adhering to this practice consistently throughout an entire growing season will reduce the number of annual and perennial weeds in your lawn this season and dramatically reduce the number that grow next year.