You have a great looking lawn. The grass is cut regularly. It gets fertilized a few times a year. It gets watered during a drought. The weed control takes care of most of the weeds, but there are a few problems that persist. In both Baton Rouge and New Orleans, nutsedge and lespedeza can be a hard weed to get rid of from your yard. We'll go through a little bit about each weed here and some tips on weed control.
How to Identify Sedge Weeds
Sedge is a general name for a group of weeds that includes purple nutsedge, yellow nutsedge, and kyllinga. We tend to have a problem with purple nutsedge and kyllinga in south Louisiana. You can identify sedge weeds easily since they are a lighter green than the surrounding grass and they grow taller than grass in a much shorter time. Sedges have a triangular stem, meaning they have three points on the base growing from the ground. Sedges look like thin grass blades until they form a group of three leaves on top which then spouts a flower.
Sedges maintain a root system of rhizomes that average a full foot or more below the ground. The root systems can spread into a patch of sedge measuring between eight and twelve feet. These rhizomes extend to what appear to be new sedge plants growing close to one another, but are actually the same plant. The root system is also attached to starchy "nutlets" that provide plenty of food when the weed is cut. These plants are perennial, meaning you will see them during the summer every year until you get rid of the weed for good.
How to Get Rid of Sedge Weeds
First, you should manage the environmental conditions of your yard. Sedges like poorly drained soil that stays moist. If you have a problem with sedges, try filling in low spots or using aeration and top dressing with sand. Second, you may be mowing your grass too low. The lowest setting on your mower should not be used to cut grass except for maybe bermudagrass. Try raising your mower setting up to one of the higher settings. The grass should thicken up and look healthier, which will crowd out the weeds. Surprisingly, your grass will actually grow more slowly since it will not have to grow as aggressively each week to gather sunlight.
How to kill the sedge in your grass? Visit a local hardware store or nursery. Seek a "sedge killer" product that is labelled as safe to use on your grass variety. Most sedge control products require at least two applications spaced a few weeks apart. You will most likely need to do the same treatment again the following year to get full control of the weed. We use products like Certainty and Sedgehammer.
How to Identify Lespedeza Weeds
Lespedeza grows into thick sections called mats. It branches out into leaves of three along the ground. Lespedeza is a summer annual. It grows leaflets out of veins which tend to grow at right angles from the main stem along the ground. If confused by the description, just compare your weed to the one pictured above.
How to Get Rid of Lespedeza Weeds
Cultural control of lespedeza involves aerating compact soils and not cutting your grass too low. Lespedeza thrives in compact soils. It also grows lower to the ground than grass, so it suffers when the grass makes shade over it. If you have a persistent lespedeza problem, check your soil pH. This weed will out perform grass if the soil pH is off balance.
Control products can be found in your local hardware store for use when controlling lespedeza. Carefully read the product label for heat restrictions. Certain products, like three-way herbicides, work well at eliminating weeds, but can burn your grass if used in the middle of summer in Louisiana. These product's results will vary. Products containing Metsulfuron are very effective in getting rid of lespedeza in St. Augustine, Centipede, and Bermuda lawns. A professionally available product called Celsius WG also controls lespedeza with impressive results. Always read and follow the label when dealing with herbicides.