Dandelion multiplies rapidly
image by DRW & Associates Inc
A weed may be just a plant that's out of place but, when the place is in your lawn, you'd probably rather it moved on. Unfortunately, most weeds are not good guests; they stubbornly hang around and bring relatives to keep them company. They can be a nuisance, or they can choke a lawn in a season. The answer is not always found in chemical treatments. Getting rid of them requires patience, some ruthless strategies and a commitment to consistent methodology.
Pull weeds when they start to appear. Quack grass, unlike crabgrass cannot be "done in" with chemicals; it grows by trailing roots called rhizomes and must be dug out and replaced with dirt and new seed or sod. One dandelion rooted out before flowering prevents thousands of summer weeds. Keeping ahead of weeds takes energy and persistence, but if your problem is small, these efforts keep it from becoming major. Remove your lawn's competition as it sprouts.
Mow properly. Mow high--2.5 to 3 inches--particularly during the heat of summer. Weeds hate shade, and lush grasses shade seedlings. Mow frequently; never remove more than one-third the length of a blade at a time. Keep lawn mower blades sharp, sharpening several times during the season if needed. Sharp blades make clean cuts, and grass heals faster, loses less water and is less likely to develop diseases or succumb to funguses.
The best way to discourage weeds is to have a thick, green lawn. Water thoroughly but infrequently to make sure your grass gets one inch of water in rain or irrigation every week. If water sits in puddles, you may have a clay soil that needs aeration---a process that pulls little plugs of topsoil out---and a top-dressing of manure or peat moss to help develop the "friability," or ability to drain water, of the topsoil.
Use the right fertilizer and herbicide blend. A nitrogen-heavy fertilizer feeds your grass, but it does not need extra phosphorus. On the other hand, weeds thrive on phosphorus. If you must use herbicides, make sure you've got the right type. Pre-emergent crabgrass herbicide should only be applied before the grass greens up in the spring and only on summer annual grasses. Broad-leaf, or post-emergent control kills a wide variety of weeds like dandelions, plantain and chicory. It should be used only before or after the gardening season because it vaporizes easily at temperatures above 80 degrees and can drift into gardens.
If your soil seems more hospitable to weeds than grass, get it tested at a local university agricultural extension to make sure that your lawn grass has what it needs to thrive and that you're growing the right variety of lawn grass for your area. Add lime or sulfur to balance your soil's pH. Plant a different variety of grass---Kentucky bluegrass is not a "grass for all seasons" and neither is fine fescue. Each has its strengths and weaknesses.