If you'd like your lawn to look as well groomed as a PGA golf course, fall is the time to take corrective measures. Before you do, though, walk across the street, turn around, and view your lawn from your neighbors' perspective. It probably looks better than you expected. A little distance disguises a lawn's minor flaws, says Oregon State University extension turf specialist Tom Cook. "A good lawn is one that looks good from across the street," he says, "because that's how most of the world sees it." If yours looks healthy, your only chore right now is fertilizing it to keep it strong. On the other hand, if your lawn is the scourge of the neighborhood, get moving.
• FERTILIZE ALL LAWNS. Both cool- and warm-season grasses benefit from feeding in early fall. Combination lawn fertilizers are a good choice, since they contain a small amount of fast-release nitrogen, which provides a quick green-up, and a larger portion of slow-release nitrogen, which continues feeding the lawn slowly and gently. Apply fertilizer as recommended on the label.
Another way to fertilize is by leaving your grass clippings on the lawn. As the clippings decompose, they release nitrogen into the turf. Cutting grass with a mulching mower, which chops the blades into finer pieces than a conventional mower, speeds up the process. By doing this regularly, you can eliminate one lawn feeding or more.
• PATCH DEAD OR DAMAGED SPOTS. Always patch with the same type of grass as the existing lawn. Remove and discard the old turf, then loosen the top 3 to 6 inches of soil in the bare section, work in compost to improve the soil, and level the surface. Then either seed, plant new plugs, or insert a fresh piece of sod cut to fit the damaged area.
• OVERSEED IF DESIRED. In mild areas of Arizona and Southern California, it is common practice in mid-fall to overseed winter-dormant grasses such as Bermuda and St. Augustine with ryegrass. Overseeding should take place when daytime highs range from 78° to 83° and nighttime lows are 55° or colder, typically between mid-October and mid-November.
Before overseeding, mow the grass very short. Mow in stages, taking off 1/4 inch or so with each of three or four passes, until you've removed 60 to 70 percent of the blades' original height.
Apply seed generously: 14 to 18 pounds per 1,000 square feet. Top-dress with composted steer manure or other weed-free mulch and keep soil moist until seeds germinate. Don't mow until the ryegrass is 2 inches tall.
• AERATE IF NEEDED. When your lawn gets heavy foot traffic, the soil underneath can become compacted, making it difficult for water, fertilizer, and especially oxygen to reach grass roots. If you can't easily push a screwdriver up to its handle into the turf, the soil is compacted and needs aeration. The remedy is to punch cylindrical holes into the soil so that the grass can breathe again and moisture and nutrients can penetrate more easily. Though manual aerating devices are available, for anything but a very small lawn you'll probably want to rent a power core aerator or hire a professional lawn care firm to do the job. Aeration works best on a moist lawn on a cool day.
• CONTROL WEEDS. If you have lots of chickweed, dock, dandelion, plantain, or other broad-leafed perennial weeds in your lawn, apply a postemergence systemic herbicide to control them (systemic herbicides circulate throughout the plant, killing all parts, including the roots). To identify weeds, take samples of your problem weeds to a nursery, where an experienced staff member can suggest appropriate chemical controls. Read labels carefully and follow directions.
For prevention of winter weeds like annual bluegrass, apply a preemergence herbicide to stop their seeds from sprouting.
Nonchemical weed controls are described below.
• WAIT TO DETHATCH. Turf experts no longer recommend dethatching lawns in early fall. Thatch is the tough fibrous layer of dead stems, rhizomes, and debris that builds up between the soil surface and the grass blades above it. When this layer gets thicker than about 1/2 inch, some of the thatch should be removed, preferably in early spring. For cool-season grasses, like Kentucky bluegrass, do this in early spring; for warm-season grasses such as Bermuda, wait until summer. Grasses recover from dethatching trauma more quickly in warmer weather.
Nonchemical weed control methods
Chemical herbicides can help you reestablish control over a lawn where weeds have gained the upper hand. But if you prefer not to use chemicals, here are some alternative measures.
• Fill bare spots as soon as they appear. If there's an empty space in your lawn, weeds will find and fill it. Don't give them the opportunity. Keep grass seed on hand and sow as thin spots appear.
• Mow high and often. The simple step of mowing high can eliminate a lot of weeds. To begin with, tall lawns are healthier. They have more leaf surface to collect sunlight and promote growth, and their roots tend to be deeper, with more access to water and nutrients. Over time, taller grass will crowd out and shade out many weeds. Cut tall fescue such as Marathon to 21/2 inches tall; annual ryegrass, buffalo grass, fine fescue, and Kentucky bluegrass to 2 inches; St. Augustine 1 to 2 inches; Bermuda and zoysia 1/2 to 1 inch. In summer, allow even more height. When you mow, never take off more than a third of the grass height at any one time; instead, mow often. Mowing frequently also helps reduce weeds by cutting off flowers before they can spread seeds.
• Off with their heads. You can kill many weeds by repeatedly cutting off their stems and leaves as close to the ground as you can. It may take a half-dozen decapitations, but eventually the weed will use up its reserves and die.
• Hand-weed. There are many weeding devices on the market, including some designed to pry out the monstrous taproots of dandelions.