An Organic Lawn
There's more to mowing
The lawn mower is your most important turf-maintenance tool. Mowing not only cuts the grass down to size, but done properly, it also helps grass grow thicker. It can reduce the weed population, too, and even feed the turf.
Every type of grass has its own preferred height. Table 20-2 lists how high to set your mower blades. For best results, mow when the grass is no more than 50 percent taller than its optimal height (see Figure 20-3). If your grass should grow to 3 inches, for example, mow it when it reaches 4>2 inches tall. In general, mow at the bottom end of the range when the grass is actively growing and at the top end of the range during times of stress or slow growth.
Table 20-2
Best Mowing Heights
Table 20-2
|
Cool-Season Grasses |
Warm-Season Grasses | ||
|
Bent grass |
14 to 3/4 inch |
2 to 3 inches | |
|
Chewings fescue |
1 to 2 inches |
Bermuda grass |
to 1 inch |
|
Hard fescue |
1 to 2 inches |
Blue grama grass |
2 to 3 inches |
|
Kentucky bluegrass |
2 to 3 inches |
Buffalo grass |
2 to 3 inches |
|
Perennial ryegrass |
1/2 to 2/2 inches |
Carpet grass |
1 to 2 inches |
|
Red fescue |
1/2 to 2 inches |
Centipede grass |
1 to 2 inches |
|
Sheep fescue |
2 to 4 inches |
St. Augustine grass |
1 to 3 inches |
|
Tall fescue |
2/2 to 3 inches |
to 1 inch |
Here's how to get the best cut from your mower:
- Make sure the blade is sharp (sharpen it at least twice per season).
- Vary the mowing direction once a month to avoid soil compaction.
- Don't mow when the grass is wet.
- Overlap by about one-third of the width of the mower deck with each pass.
- Clean the grass off the mower after each mowing.
One of the best things to happen to the organic lawn is the mulching mower, which pulverizes grass clippings into smaller pieces than a conventional mower does. Grass clippings are probably the best fertilizer your lawn can get because they provide free and natural nitrogen. When chopped into little bits, the clippings begin to break down into useful nitrogen almost as soon as they hit the ground.
Figure 20-3:
Mow when grass reaches 50 percent taller than the recommended height.
Watering awg/
People spend a lot of time, effort, and money keeping their lawns watered. In many parts of the country, that effort is wasted, because the lawn can survive the summer without any supplemental water. To withstand periods of drought, many types of turfgrass enter dormancy. They stop growing and turn brown. But when the rains return, the grass springs back to life. Sometimes, raising an organic lawn means putting up with an unattractive lawn for a while instead of using precious water resources. If and when you do irrigate your lawn, you must water deeply and slowly. Follow these tips:
✓ Water long enough to moisten the soil to a depth of 6 to 12 inches.
The amount of time it takes to achieve this goal depends not only on the sprinkler, but also on the type of soil under the lawn.
Standing out on the front lawn in the evening with a hose in hand does more harm than good. You'd have to stand out there for hours and hours to apply an adequate amount of water. Plus shallow sprinkling makes the roots lazy; if they get a little bit of water regularly, they become conditioned to staying near the surface of the soil. If you stop watering, your lawn will die of drought because the roots haven't grown deep enough to forage for their own water.
✓ Apply water slowly enough so that it doesn't puddle or run off your lawn. Look for a sprinkler with a low flow rate of less than % inch of water per hour, especially if you have clay soil. On such heavy soil, you may need to cycle your watering by turning the water on for 15 minutes, off for 15 minutes, on again, and so on.
In general, high-quality oscillating and impulse sprinklers offer the most uniform coverage and cover the most ground.
The best time of day to water your lawn is early morning, which features cooler temperatures. You'll lose less water to evaporation than at midday, and the grass blades will dry quickly, minimizing disease problems.
Feeding the lawn
Grass needs more nitrogen than any other nutrient for strong growth, and because it grows almost continuously, it needs a constant supply. Grass clippings themselves provide some natural fertilizer, but you can use several other organic materials to feed your lawn as well.
Natural fertilizers contain nitrogen that doesn't dissolve readily in water but ' " needs a little help from soil microorganisms to become available for plants.
That's good. It means that the nitrogen is released slowly, and consequently, the lawn grows slowly and steadily. Synthetic chemical lawn fertilizers, on the other hand, tend to release lots of nitrogen all at once, which makes the lawn grow fast at first, adding to your mowing chores. Also, chemical lawn fertilizers are among the largest sources of water pollution in the country.
Figuring out how much fertilizer you need
Your lawn probably needs less nitrogen than you think. You can figure out how much nitrogen to apply by using the following steps:
1. Find the amount of actual nitrogen required by the type of grass in your lawn.
Cool-season fescues need 1 to 3 pounds of nitrogen per year per 1,000 square feet. Kentucky bluegrass and perennial ryegrass need 2 to 3 pounds, and bent grasses prefer 2 to 6 pounds. Warm-season blue grama and buffalo grasses need only K to 1 pound of nitrogen; Bermuda and carpet grasses need 1 to 3 pounds; Bahia, centipede, and zoysia grasses need 2 to 3 pounds; and St. Augustine grass needs 3 to 6 pounds.
If you don't know the predominant type of grass in your lawn, dig up a sample and take it to your local extension office or a full-service nursery for identification. Or start with 1 pound of actual nitrogen per 1,000 square feet twice a year; that's a safe maintenance dose.
2. Find the percentage of actual nitrogen in the fertilizer you want to use.
See Chapter 6 for naturally nitrogen-rich fertilizers and the percentage of nitrogen they contain.
3. Plug those numbers into the following formula to determine exactly how much material you need to feed your lawn:
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Pounds of nitrogen that grass requires per year * percentage of nitrogen in the fertilizer = pounds of fertilizer required per year per 1,000 square feet.
Kentucky bluegrass, for example, requires 2 pounds of actual nitrogen per year, per 1,000 square feet. A bag of 10-6-4 organic lawn fertilizer contains 10 percent actual nitrogen, and 2 divided by .10 (10 percent converted to decimal) equals 20. So 1,000 square feet of Kentucky bluegrass would require 20 pounds of 10-6-4 fertilizer per year.
4. Divide the pounds of fertilizer required per year by the number of applications you plan to make.
If you plan to fertilize your lawn twice, for example, divide the answer you get in Step 3 by 2 to find the amount you need for each application.
Just by leaving the grass clippings on the lawn to decompose, you're adding the equivalent of about 1 pound of nitrogen per 1,000 square feet. Consider this fact in your fertilizer calculations.
Many homeowners think of their property in terms of acres rather than square feet. A %-acre lot is roughly 10,000 square feet. Subtract the square footage of nonlawn areas to get the approximate size of your lawn.
Knowing when to feed
Most folks go into a lawn-feeding frenzy at the first sign of spring, but for most of the country, that's not the best time to feed the grass. It's better to fertilize in autumn in cold climates. That practice helps the grass grow strong and packs away some nutrients for the following year. In warmer climates, the best time to feed is late spring, after the grass breaks out of dormancy and begins to grow again. Warm-season grasses need regular feeding to survive the stressful summer months. Cold-season grasses usually can get by with just one or two feedings per year.
If you want to green up your lawn quickly and naturally, use a hose-end sprayer to apply liquid seaweed. The iron in the seaweed encourages a rich green color.
Thinking about thatch
As grass plant parts die, they can form a tangled mat of undecomposed or partially decomposed organic matter on the surface of the soil called thatch. A little thatch is a good thing. If it's less than % to K inch thick, thatch helps cool and cushion the soil, as well as conserve moisture. Thick thatch may cause problems, however. A layer more than K inch thick keeps water and nutrients from reaching the soil and provides a cozy home for turf-destroying insects and diseases.
If thatch builds up on your lawn, remove it, or dethatch the lawn. For small areas, you can use a thatch rake (sometimes called a cavex rake) to scratch the thatch from the soil. This job is backbreaking work, however, so try it only on small lawns. For large areas, rent a dethatcher (also called a vertical mower). This gasoline-powered device cuts the thatch and lifts it to the surface, where you can easily rake it up.
Loosening the soil
The soil under a lawn takes a lot of abuse. You walk and run over it, stand on it, run a heavy mower over it regularly, and sometimes even drive over it. The result is compaction that slows the growth of the grass. With you can't turn and condition the soil every year for a lawn, there is a specialized way to cure lawn compaction and invigorate the soil: aeration.
Aeration is simply the process of creating holes in the turf. Done right, it removes cores of compacted soil, leaving room for air, water, and nutrients to penetrate. On small lawns, you can aerate by hand. For less than $20, you can buy a hand aerator that uses foot power to remove cores of soil. For large lawns, you can rent a power aerator from the local tool-rental shop. Steer it over the lawn like a lawn mower as it jams its tines into the turf, removing cores of soil in the process.
With either implement, the next step is to break up the cores and leave them on the surface of the lawn to decompose — or, if you find the waste too unsightly, rake it up and toss it into the compost heap. If you use your lawn heavily, aerate once a year, just like they do down at the ball field.
Top-dressing
Most lawn owners neglect one very important organic lawn-care practice: top-dressing, which is simply spreading a thin layer of organic matter over the lawn. No, it's not fertilizing per se, but it does improve the soil and can provide nutrients depending on the material used. Top-dressing is vital because you don't dig up the lawn every year; the only way to improve the soil is from the top down.
Top-dressing is a simple process. In autumn, spread a very thin (about % inch deep) layer of organic matter over the lawn. Use topsoil, shredded compost, or any other organic matter. The material works its way down through the sod, with the help of earthworms and other critters, to improve the texture of the soil. You can make the process even more effective by aerating the turf first (refer to "Loosening the soil," earlier in this chapter).
Weeding
The best way to defeat weeds is to grow a healthy, thick sod. Fertilizing, watering, and mowing properly all make the grass thicker, which makes it tougher for weeds to get a foothold. In fact, correct mowing alone can help control certain types of weeds. University experiments show that mowing a bluegrass lawn at a height of 2 inches helps reduce the amount of crabgrass in a lawn significantly. Mowing your lawn higher helps the grass outcompete low-growing weeds, such as crabgrass and creeping Charlie.
You can also use old-fashioned elbow grease. When you find weeds in your lawn, pull 'em or chop them out. Long-handled specialty weeding tools for the lawn, such as the Houn Dog Weeder and the Speedy Weeder, make a surprisingly fast and easy job of pulling dandelions, plantain, and other lawn weeds.
Recently, some natural herbicides have become available that give organic-lawn owners a lucky break. Corn gluten meal is a highly effective natural turf herbicide. It works as a pre-emergent to kill sprouting plantain, creeping bent grass, dandelion, and many other weed seeds. Apply 25 pounds per 1,250 square feet in spring before weeds begin to sprout. Don't apply it to newly seeded lawns, however. Corn gluten meal also contains about 10 percent nitrogen, so it serves double duty on the lawn. For already growing weeds, you can also try Sharpshooter, a broad-spectrum, soap-based organic herbicide that kills all vegetation on contact. Use it with caution, because it kills grass as well as weeds. For more on weeds and weeding, turn to Chapter 11.
Perhaps the best way to deal with weeds is to change your definition of them. Take clover, for example. Just because clover isn't a grass plant doesn't mean that it doesn't belong in the lawn. Clover stays green through tough weather, recovers nicely from mowing, and is soft and cushiony. Also, unlike grass, it increases the fertility of the soil by taking nitrogen from the air and making it available to plant roots in the soil. Other so-called weeds, such as yarrow and Roman chamomile, attract beneficial insects.
Managing pests
Although a long list of insects may chow down on grass, only a few pests really do serious damage to turfgrass, and organic treatments exist for all of them. The most notorious and damaging turf pest is the grub, which is an immature beetle that lives in the soil. Grubs, especially the larvae of Japanese beetles, can do a number on turf. They feast on grass roots and kill the plants in the process. Pull up a patch of sod, and if you see a dozen grubs per square foot, it's time to take action. Here are two biological controls for grubs:
- Milky spore disease: This bacteria species infects and kills grubs. Apply at a rate of 4 ounces per 1,000 square feet any time the grubs are active. It works best in areas where the soil temperature remains above 70 degrees Fahrenheit for several months a year.
- Beneficial nematodes: Spray these microscopic worms onto the soil, and they begin killing grubs within 48 hours and continue their grub-killing duty for months. In the process, they also eliminate cutworms and armyworms. Flip to Chapter 8 for more on milky spore disease, beneficial nematodes, and other safe pest controls.
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Intensive turfgrass breeding has yielded several new varieties of grass that actually resist damage from greenbugs, armyworms, billbugs, cutworms, and sob webworms. Look for the tall-fescue variety Apache and several perennial varieties, including Premier, All Star, Cowboy, Prelude, Sunrise, Pennant, Citation II, and Repell. Also look for endophyte-enhanced lawn seed mixes that minimize insect damage (refer to "Best grass for trouble spots," earlier in this chapter).
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