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Grass is highly competitive and can grow thick enough to out compete weeds. Healthy soil and over-seeding in September will give your grass an edge over weeds. You can also give grass an advantage by mowing or removing weed plants before they get too big or set seed. Be sure to sprinkle grass seed in the bare areas after weeding, since newly exposed weed seeds will begin to grow otherwise.

Manual Methods
Corn Gluten Meal
Contact Herbicides
Borax
Solarizing
Smothering

Manual methods
Most weeds can be successfully hand weeded after a rain when the soil is loose and moist. Weeding is most effective in the spring (April or May) when the plant's food reserves are at their lowest. Because of this, root remants are less likely to grow back.

If visions of hand weeding bring to mind back-breaking hours spent on hand and knee, think again. Better tools make weeding easier. Weeds with taproots, such as the dandelion, can be attacked with a waist-high pronged grabber tool, such as the "Speedy Weedy" or "Grab It Weeder." No bending is required. With one of these tools and moist soil, you can extract 4-8 dandelions per minute, or more than 100 in half an hour. It's easier to do if you tackle small areas at a time. Make a game out of flicking the roots into a pail and the time goes quickly. These pronged grabber tools have another advantage: they are able to pull out the root without disturbing much of the surrounding grass. That means less over-seeding, less work and less expense in grass seed.

Creeping Charlie, with its low growing mat of rooted horizontal stems, requires special manual weeding methods. Hand weeding can be effective if the weed has not taken over a large area; if it has, consider smothering or solarizing. Weed Creeping Charlie when the soil is moist, as the multitude of tiny rootlets will lift more easily out of the soil. One strategy is to rake it out of your lawn with a stiff rake such as a bow rake, or use a small metal kid's rake. Rake in two directions and remove the bits of stems. Some people use a hammer-type dethatching rake. Others use a garden hand "fork" to hook the runners and pull it up.

Spring is the optimal time to rake Creeping Charlie, especially early May when it is in bloom. If you weed it in the fall, the remaining root fragments have enough carbohydrate reserves to carry the plant through spring. Creeping Charlie is relentless, and quick to re-establish itself. Once you are rid of it, be sure to prevent this weed from entering your yard again. Maintain a weed-free mulched area around the perimeter of your yard, or create some other barrier. Walk the lawn periodically looking for new runners and remove them before they take over.

Once you've extracted weeds from your lawn, compost them. If you have a good "hot" compost pile, weed seeds will be cooked to oblivion. But if your compost pile tends to be on the cool side, be aware that the finished compost will contain some weed seeds. Some plants even set seed from bloom after they are weeded. If this is a special concern, or if you don't have a compost pile, you can bag your weeds and set them out with the trash.

Corn Gluten Meal
Corn gluten meal is a safe, organic product that kills germinating weeds and adds nitrogen to soil. While it will not hurt established weeds or grass, it is a very effective pre-emergent herbicide for crabgrass. Continued research on this relatively new product shows that corn gluten meal also inhibits the seedlings of barnyard grass, foxtails, dandelion, lambsquarter, pigweed, purslane, and smartweed. Expect 50-60% control over weed seedlings the first year you use corn gluten meal; continued use in subsequent years insures you are reducing future generations of seed-producing weeds.

Timing is critical when using corn gluten meal. Because it stops root formation, it's important to apply this product just as seeds are germinating. In southern Wisconsin, the timing will vary from year to year, depending on weather. Typically, weed seeds will germinate in mid to late April. Another factor in the effectiveness of corn gluten meal is soil moisture. If the soil stays moist during the narrow window of time that corn gluten is effective, then seedlings can grow a second set of roots and weed control fails. Worse yet, the additional nitrogen in the corn gluten then helps boost weed growth.

Apply corn gluten meal at the rate of 12 lbs/1000 ft2 with a spreader in the early spring. Some experts suggest the best time is when forsythia bushes are blooming. If you still have crabgrass by summer, make a second application in early to mid-August, after crabgrass has set seed.

Each 12 lb./1000 ft2 application supplies one pound of nitrogen. Two corn gluten applications along with the practice of leaving grass clippings on your lawn, should supply about 2-3 lbs./1000 ft. of nitrogen. That's all the nitrogen your lawn should need. Remember, too much nitrogen can harm your lawn, and our groundwater. One other caveat about corn gluten meal: never use it on newly seeded lawns. It will stunt germinating grass seedlings.




Contact Herbicides
Boiling water, soap solutions and vinegar can kill many weeds on contact. These contact herbicides are non-selective. They kill the good along with the bad, so use them only for spot treatments.

Boiling water kills plants by "cooking" them. It works well on shallow-rooted weeds, but tap-rooted plants such as dandelions, may require repeated applications.

Vinegar and herbicidal soaps kill plants by destroying the plant above the surface, ending its ability to photosynthesize. Keep vinegar and soaps away from surrounding plants by coating it on the leaves with a sponge or a foam paintbrush, or by protecting the neighboring plants with plastic or cardboard while you direct a spray with a hand held bottle.

When using vinegar, choose a solution with 5-20% acetic acid. Kitchen vinegar is 5% and is adequate for sidewalk crack weeds. A stronger solution of acetic acid is a more effective weed killer, but may also cause injury if splashed into the eyes. Use good judgment when handling vinegar or any acidic substance. Also keep in mind that repeated applications of vinegar can lower the pH level of your soil. If the pH of your soil drops below 6.0, you can restore it by adding agricultural lime.

To make your own herbicidal soap, use use a concentration of 4 ounces of liquid dishwashing soap in 2 gallons of water applied to 1000 ft2 . This concentration will not harm grass.



Borax
Long ago, in the days before washing machines but after the invasion of Creeping Charlie, people discovered that wash water dumped on lawns killed this ground ivy. Modern research, however, show that this weed control method is inconsistent at best. Soil moisture and temperature are critical. Studies at Iowa State University showed that Borax reduced a Creeping Charlie infestation in turf grass, but results were weather-dependent. The Iowa studies also found that borax can injure turf and other plants as well, causing stunting and yellowing. Studies in Wisconsin, however, showed Borax was not an effective control of this weed due to soil conditions.

Creeping Charlie is extremely sensitive to boron. A little too much in the soil will kill the plant. However, the availability of boron in the soil depends on soil type and pH. These factors affect the outcome of applying borax, as in the Wisconsin trials. Too much boron, and you could kill your grass as well as Creeping Charlie. Worse yet, boron does not break down or dissipate. It may persist in the soil for years. If you try once and fail, you can't try again. There is little room for error with borax applications.

One recipe calls for spraying boron at a rate of 10 ounces of Mule Team Borax to 2.5 gallons of water. But other recipes call for more or less borax. These conflicting recipes and the risk of damaging your turf makes borax a risky endeavor.




Solarizing
The easiest way to deal with severely weed-infested turf may be to start over by "solarizing." Solarizing captures heat from the sun to "cook" all plants and weed seeds in the top layer of soil. Consequently solarizing offers more long-term control than herbicides. Herbicides mainly control germinating seedlings and growing plants. They do not necessarily keep dormant weed seeds from germinating in the future.

Solarizing will only work in an area that receives at least 4 hours of direct, mid-day sunlight. For shady areas, see the section on smothering. When solarizing, be patient: allow two to four weeks, depending on the weather. Your staying power will pay off with a weed-free base on which to plant.

The basic solarizing technique is simple: