Controlling lawn weeds can seem like a constant battle -- but the war can be won, says Tammy Algood, home garden expert with the University of Tennessee Agricultural Extension Service.

The main culprit is weed seeds and roots in the soil. As the lawn is worked on, these seeds and roots are pulled to the surface and germinate. Weeds are also carried into the lawn by wind, birds and mowers -- even by walking across it.

The best way to eliminate weeds is to pull them by hand as they appear. Make a daily inspection of the turf, with weeding tools in hand. Weeding is easiest when the soil is wet from irrigation or rain. When the soil is moist, even tough weeds such as dandelions just slip out of the ground. The roots on some weeds become quite large after the foliage has been mowed down a few times, so get them while they're young.

Dead nettle, a low-growing invasive annual weed, enjoys the same kinds of growing conditions favored by turf grasses. It has a square-shaped stem and produces purple flowers. Henbit, another weed, looks very similar. Chickweed, another annual, is low-growing, with tiny bright-green leaves.

Perennial weeds such as wild strawberry are more difficult to control because they spread by underground runners or stems. White, or Dutch, clover can often be eliminated with regular applications of fertilizer. Dandelion, a perennial weed, grows in all zones. Pull dandelions by hand, making sure to get the entire thick root. A fish-tailed hand-weeding knife is an effective tool.

Wild garlic is difficult to control by hand. In order to eliminate it, all of the tiny bulbs in the soil must be pulled up. Probably the best hand remedy for a severe infestation of this weed is to solarize (cover the affected area with plastic for at least eight weeks to kill all vegetation), then start the lawn all over again. If a chemical control is preferred, use a selective herbicide containing dicamba. Chemical control is only partly effective against wild garlic, even with repeated sprayings.
Chemical control with herbicides may be necessary for a large lawn or a lot of weeds. Pre-emergent herbicides prevent weeds from germinating by creating a barrier of gas in the top few inches of soil that weed seeds can't penetrate. After applying a pre-emergent herbicide, it's necessary to water in order to activate the gas.

Post-emergent herbicides kill weeds after they have germinated. Some are selective, killing only broadleaf, clover or grassy weeds; others kill plants indiscriminately. Round-Up and Finale are examples of common nonselective herbicides.

Read the label carefully to make sure the product selected will do the job, and follow the manufacturer's instructions to the letter. Always wear long-sleeved shirts, pants, eye protection and neoprene gloves when spraying herbicides. Plain rubber gloves may not protect skin from absorbing the harmful chemicals.

Never spray herbicides on a windy day. The fine chemical particles will drift in the wind and may harm garden plants. When cleaning the sprayer, work over soil, never over concrete, from which the pesticide may be washed into storm drains and eventually waterways. Even small amounts of pesticides may kill aquatic life, including fish and amphibians.

A healthy lawn is the best defense against invasion by weeds. Keep the lawn healthy by removing thatch as needed, mowing at the correct height and fertilizing and watering correctly, so that weeds will have a harder time becoming established.