There's something soothing about seeing an even expanse of green grass that just seems to lower our blood-pressure a bit. And to some people, when that expanse is broken up by something growing where it shouldn't be growing, it also seems to raise it a notch or two.
Weeds are really just one type of plant that we have decided shouldn't be growing in one particular place. Wild orchids growing in Hawaii are considered weeds. It's just your point of view as to what makes a weed a weed. Some weed-type plants are invasive and fast growing. Their growth habit overtakes our cultivated turf plants, depriving them of food and water. Other weeds are extremely noxious and cause problems for humans if they get close them.
In the lawn, the most common weeds are just a nuisance. Most don't cause skin reactions or breathing difficulties, they just don't look good. What they're also telling us is that the lawn isn't as healthy as it should be. Turfgrasses today are so adept at growing into thick masses, that if maintained properly, weeds are not a problem. It is when the lawn isn't as healthy as it could be that we see weeds becoming a problem for the lawn.
Some common lawn weeds are annuals. Sprouting from seeds, they develop, blossom and form new seeds, then die in the fall, repeating the process each year. Crabgrass is one such weed. Once these types of weeds take root, they are difficult to remove without harming the lawn. The ideal control prevents them from developing in the first place.
Applying a Pre-emergent Control in the spring does this. The soil's surface is covered with a microscopic protective layer that prevents any germinating seeds from taking hold, including crabgrass. If left undisturbed, this protective layer will maintain its defensive qualities throughout the prime germinating period. This is when most weed seeds will normally start developing. Of course, there is no 100% guarantee that additional seeds won't be carried in by winds, birds, or any number of other methods.
Thoroughly read, understand, and follow all information on herbicide labels. Avoid windy days, as these materials can damage many landscape and garden plants if they drift (spray droplets land off the lawn). Also avoid hot days (over 85 degrees F). It's best to have adequate soil moisture, but no rain for 24 hours after application. Don't mow for a few days before and after application. Consider spot treating weeds rather than broadcasting weed killer over the entire area. Use caution on newly seeded areas; wait four mowing's before treating newly seeded lawns and 30 days before seeding areas treated with broadleaf herbicides. Read the label regarding potential tree damage when used on lawns growing over tree root zones.
To treat for weeds in your lawn, you have to understand the type of weed that you have. Since different type weeds require different types of treatment. Below is a link to help you better identify your weed.
Don't fertilize lawns in the spring for cool season grasses. Don't fertilize warm season grasses in the winter.
Mow cool season grasses high in the spring and warm season grass high in both the winter and spring.
Rake the lawn in early spring with a metal garden rake to raise the creeping weed stems
Mow the grass low after raking
Collect and dispose of the clippings to remove the weed stems to prevent them from re-rooting.
Don't fertilize lawns in the summer
Mow at recommended height, but use a bagger to collect clippings while weed seed heads are present.
These are mostly grassy weeds that spread quickly when cool-season turfgrasses are stressed and struggling with the heat of the summer. They include nimbleweed and some warm-season grasses growing in cool-season lawns.
Remove clumps of these weeds, root, rhizome and all.
Mow high to reduce the stress on desirable grasses.