Apply a Preemergent Herbicide
The easiest way to stop crabgrass is to nail it before it starts growing. Apply a preemergent herbicide after your second mowing in the spring. Crabgrass grows from seeds scattered in previous years. The herbicide keeps those seeds from germinating. The seeds may remain viable for several years, so it's best to apply herbicide every spring. One springtime application will vastly reduce the need to attack crabgrass later in the year once it has sprouted.
Save Your Lawn Products
Leave a bag of fertilizer or weed killer open for long and it'll soak up moisture from the air and won't go through a spreader. Even grass seed could use an extra layer of protection from a moisture-wicking concrete floor. Place opened bags of lawn products in large resealable plastic bags ($1 at discount stores). The products will be free of clumps or pests when you need them.
Set Your Blade at the Right Height to Control Weeds
Cutting grass too short weakens it. Longer grass grows stronger and thicker and crowds out weeds. Weed seeds can't germinate easily since they don't get much light. Established weeds have a tougher time competing with the surrounding turf.
Each type of grass has an ideal mowing height to maintain its health and thickness. It's about 2-1/2 in. for most cold-climate species. Cut most warm-climate grasses a bit shorter: 1-1/2 to 2 in. If you're not sure of your grass type, take a sample to a local nursery. Or type 'identify grass' into an online search engine for help. Although most lawns contain a mix of grass types, they should have similar ideal cutting heights.
For Healthy Grass, Adjust Your Soil pH
Soil pH (acidity level) is very important, and just because your dirt looks rich and black doesn't mean it's the right pH for grass. Take samples around the yard and get them tested. If the pH is too low (acidic) or too high (alkaline), the grass isn't happy to be there. But you can fix the problem by adding lime to raise the pH or iron to lower it. Most grasses prefer a pH of 6.0 to 7.2.
Note: Lawn and garden centers sell do-it-yourself pH testers; more accurate tests can be performed by extension services.
Healthy Grass Is the Best Weed Preventer
Lawns that are nutrient-stressed are a breeding ground for weeds, so the best defense is a healthy lawn.
Test the soil to see what type and quantity of fertilizer is needed to help your lawn. Proper fertilization improves lawn health, so grass can compete better and crowd out weeds— without a lot of weed killer.
The Best Lawn Advice is Locally Grown
One-size-fits-all doesn't work for fertilizer, weed killer and grass seed, even though that's what the chain stores sell. Lawn products that work great in Georgia clay may not be good for Kansas or Oregon. The best way to find out about growing conditions in your area and what to put on your lawn, and when, is to talk to a local garden center or your agricultural extension service.
Broadcast Spreader Technique
Broadcast spreaders do a great job of spreading grass seed, fertilizer and weed killer on larger lawns because they throw the material out more consistently over a wide area. However, unless you know how much area they cover for each type of product, you can end up spreading too much or too little and get bad results.
The best way to find out the actual dispersal pattern for your broadcast spreader is to do a test run on your driveway and then measure the results. Clean off a 12 x 20-ft. section of the driveway. Close the flow lever on your spreader and set the controls for the product you're using. Fill the spreader—do this on the driveway or sidewalk to avoid spills on the grass—then open the flow lever and push the spreader several feet down the center of the driveway at your normal pace, continuing for a few steps after you close the hopper.
Measure the average dispersal pattern to the sides and front. (Note: The right side of the dispersal pattern for spreaders is wider than the left side.)
Sweep up the test material and dump it back into the spreader, then apply the material to your lawn, walking back and forth in the long direction on your lawn (Figure A). Overlap each course 6 to 12 in., but close off the flow when you make tight turns.
Walk the spreader up the center of the driveway, then measure the total width and the width on each side.
Apply a 'header strip' around the perimeter of the yard, then fill in the middle. Shut off the spreader when you turn.
Feed Shady Areas Less
People tend to overapply fertilizer to shady areas because the grass is struggling. But that just kills it faster!
Many people really have two lawns—a lawn that gets full sun for most of the day, and a shaded lawn that may get only two to four hours of direct sun—and their water and fertilizer needs are different. The grass in shady areas needs less water because less evaporates, and it needs less fertilizer because with less sun it doesn't grow as much. When you go into shade, shift the controls on the spreader so you're spreading about half the amount.
Reseed Bare Patches
Late summer and early fall are the best times to reseed any dead areas. Summer is just too hot for the seed to thrive. Water the new seed a couple of times a day until the grass is about 1-1/2 in. high. Don't use normal fertilizers, however. Use a product like Scotts Starter Fertilizer, which is formulated for new grass. Spread the seed so that you have about 15 seeds per square inch. Don't overdo it or the grass won't thrive due to overcrowding.
Fertilize in the Fall
If you want the best lawn in town, fertilize four times a year. But you can keep it simple and still have a great lawn if you only fertilize once—in the fall. Choose a fertilizer that's labeled 4-1-2. (Those numbers refer to the percentages of nitrogen, phosphorus and potassium in the fertilizer.) Better yet, ask an expert at a garden center for advice about the best fertilizer blend for your grass type and local soil conditions.
Apply the fertilizer about three weeks before the last mowing of the season. Fertilizing in the fall provides energy and nutrients for the grass roots as they multiply in cooler weather before the grass goes dormant. The roots store food for the winter as well, which gives the grass an initial growth spurt when it emerges from dormancy in the spring.