You can get rid of weeds in your Tennessee lawn and optimize the growth of the grass, whether you have warm season or cool season grass. Warm season grass includes common Bermudagrass, hybrid Bermuda, centipedegrass and zoysia. Cool season grass includes fine fescue, Kentucky bluegrass, perennial ryegrass and tall fescue.
It is important to know the mowing height for the type of grass you have. Keeping the grass at a certain height discourages weed growth by blocking sun that the weeds need to germinate and grow. Warm season grasses should be mowed at a minimum of 3/4 inch to 1 inch in height, depending on the type of grass. Cool season grasses should be mowed at a minimum of 1-1/2 to 2 inches in height, depending on the type of grass.
Lawn grass needs an inch to an inch and a half of water weekly. Tennessee does not get enough rain to provide enough water for lawns. Tennessee lawns should be watered between 5 a.m. and 10 a.m., with at least an inch of water weekly. An inch to an inch and a half of water should moisten the soil to a depth of 4 to 6 inches. Giving the lawn enough moisture reduces disease, keeping the lawn's strength up. The stronger that the lawn is, the fewer weeds that can get enough sun to grow and take over the lawn. Do not water during the afternoon, as the sun evaporates too much of the water. Watering in the evening allows the moisture to stay on the grass for a longer period of time, which encourages disease.
In Tennessee, the soil is often on the acidic side, and needs to be limed. During the spring, test for soil pH and for lacking nutrients (pH kits and nutrient kits are available at a nursery or big-box gardening store). Lawns need nitrogen, phosphorus and potassium. If the nutrient test shows that the soil is not lacking in nutrients, use a low-nutrient fertilizer, such as 5-5-5. If the lawn is lacking in one particular nutrient, choose a fertilizer that is higher in the missing nutrient. Nitrogen is the first number, so if the lawn is lacking nitrogen, choose a fertilizer that is 10-5-5.