1. A thick, healthy lawn is the first step. All steps can be done simultaneously, but if you're on a limited budget, attend to the lawn (the grass, not the weeds) first. At Olive Nursery we know that healthy soil grows healthy grass, and poor soil leads to weeds, disease and insect problems. Our West Texas soil can be improved rather quickly, with encouraging results. (Please see our "Organic Lawn Care Program") The following is a list of area grasses and their perspective ability to choke out weeds: St. Augustine, Fescue, Bermuda, Zoysia, and Buffalo.
2. Pre-emergent Herbicides are the next step. These products do not get inside the seed and prevent it from starting to grow. Applied properly, these herbicides settle in the top half inch of soil, waiting on the first root to emerge from germination. If the herbicide is active and strong enough, the root will be damaged beyond repair and the germination process is failed. Pre-emergents generally last for two to six months; however, they are much more effective in the first weeks than in the last weeks. This is why timing is emphasized. Another important consideration is the target weed. Some weeds begin to germinate when it gets warm; others when it begins to get cool. Some do in January - February and others never till after mid-March. So if you apply a two-month pre-emergent in January to control Sandbur that begins to germinate in April, you probably wasted your time and money. Also weeds are generally grassy weeds or broadleafs (monocots or dicots). The veins in the grassy weeds' leaves run parallel. Broadleafs usually have a center vein with offshoot "tributaries" and the leaves are more rounded. This is important because not all pre-emergents control both. (Ask about Barricade, Team, and Dimension)
3. Post-emergent control occurs after the weed is growing in you lawn. Selective herbicides have been developed to kill target weeds without hurting your lawn. Round-Up is an example of a non-selective herbicide (it will kill grass and weeds). These products only work if they get inside the target plants. This is most often the biggest challenge to effective weed control. Almost all are designed to enter into the leaves. This happens easiest when the plants are growing, usually in the morning (and dew is great), and if the herbicide spreads out and sticks to the leaf (as opposed to rolling off the leaf onto to ground). Spreader-Sticker greatly improves effectiveness. Some herbicides target grassy weeds, others broadleafs, and some do both. Also the type of sprayer makes a difference. A tiny homogeneous droplet is best able to stay on the leaf. These droplets are best produced by pressure or tank sprayers. Hose end sprayers do work, but produce large droplets of questionable concentration. (Ask about Weed-Free Zone.)