Turf Grass Care

A lawn is a crowd of living plants, and most lawn problems start with treating every lawn the same. The right height for one grass will kill another. Water at the wrong time invites disease. Fertilizer in the wrong season feeds weeds. Once you know what is growing, when it grows, and what it needs, most of the decisions make themselves. Everything else, including machines and irrigation, exists to support the plant.

What You Will Be Able to Do

• Tell cool-season from warm-season grasses and name common types
• Set a mowing height and use the one-third rule
• Plan watering, feeding, aeration, and overseeding around the season
• Recognize common weed, insect, and disease problems
• Apply products within the law and the label

Know the Grass

Grasses fall into two groups based on when they grow best.

Cool-season grasses grow most in spring and fall, when it is about 60 to 75 F. They slow down or go dormant in hot summers. They are common in the North.

Warm-season grasses grow most in summer, at about 80 to 95 F. They turn brown and go dormant in winter. They are common in the South.

The middle of the country is a transition zone where both can struggle.

Rhizomes are underground runners. Stolons are runners on the surface. Grasses with runners fill bare spots themselves. Bunch grasses do not, so bare spots need reseeding.

Hybrid bermudagrass is usually cut lower than common bermudagrass, as low as 0.5 to 1.5 inches.

Height and the One-Third Rule

Grass makes its food in its leaves. Taller grass means deeper roots and more shade on the soil, which holds moisture and blocks weed seeds.

Never remove more than one-third of the blade at one time. If the target height is 3 inches, cut when the grass reaches about 4.5 inches.

Worked example. A tall fescue lawn is held at 3.5 inches. One-third of the finished height is about 1.75 inches, so it should be mowed by 5.25 inches. If it has grown to 8 inches during a rainy spell, do not take it all down at once. Set the deck to 5.5 inches, then lower it over the next few cuts.

Cutting too much at once is called scalping. It exposes stems and soil and badly stresses the turf. Weeds move in next. In summer heat, raising cool-season grass by about 1/2 inch helps it cope.

Soil

Test soil every 2 to 3 years. A test shows pH, nutrients, and organic matter, and it tells you what to add so you do not have to guess. Most turf does well at a pH of about 6 to 7. Your local extension office can run a test.

Compacted soil squeezes out air, so roots struggle. Foot traffic and machines cause most compaction.

Aeration

Core aeration pulls small plugs of soil out of the ground. This relieves compaction and helps air, water, and roots get in. Spike aerators only push holes and can pack the soil more.

• Work when soil is moist but not soggy.
• Make two passes at right angles for even coverage and better relief.
• Cool-season turf is aerated in early fall or spring. Warm-season turf is aerated in late spring or early summer when it is growing.

Overseeding

Overseeding means adding seed to existing turf to thicken it. For cool-season lawns, early fall is the best time, because the soil is still warm and the air is cooling. Do it right after aeration so seed lands in the holes. A typical rate for a cool-season blend is about 4 to 6 pounds per 1,000 square feet, but check the seed bag. Keep the seedbed moist until the seed sprouts.

Watering

Most lawns need about 1 inch of water per week from rain and irrigation combined. Apply it in 1 or 2 deep sessions. Deep, infrequent watering pushes roots down and builds a lawn that can handle drought. Light daily watering keeps roots shallow.

Water in the early morning, around 4 to 8 AM. Less is lost to evaporation, and the grass dries during the day. Grass that stays wet at night is more likely to get disease.

To check moisture, push a screwdriver into the soil. If it goes in about 6 inches with little effort, the soil is moist.

Feeding

Fertilizer labels show three numbers: nitrogen, phosphorus, and potassium. Nitrogen drives growth and color. Rates are usually given in pounds of actual nitrogen per 1,000 square feet.

Worked example. You want to apply 1 pound of nitrogen per 1,000 square feet with a 24-0-6 fertilizer. That product is 24 percent nitrogen, so 1 divided by 0.24 gives about 4.2 pounds of product per 1,000 square feet. On a 5,000-square-foot lawn, you need about 21 pounds.

Timing for cool-season turf:

• Early spring: A light feeding with slow-release nitrogen. Heavy spring feeding pushes top growth at the expense of roots.
• Fall: The most important feeding, to build roots and stored food.

Warm-season turf is fed while it is actively growing, from late spring through summer.

Many states and cities restrict phosphorus in lawn fertilizer, limit fertilizer near water, or set dates when it cannot be used. Check the rules where you work. Sweep product off pavement so that it does not wash into storm drains.

Calibrate your spreader. Too much fertilizer burns turf and pollutes water. Overlap your wheel tracks, and shut the spreader off during turns.

Leaving clippings on the lawn, called grasscycling, returns nutrients to the soil and reduces how much fertilizer you need. Clippings do not cause thatch when you mow often enough.

Thatch

Thatch is a layer of dead and living stems and roots between the soil and the green blades. A thin layer is fine. Over about 1/2 inch, it blocks water and can harbor pests. Core aeration helps, and dethatching machines can remove heavy layers, but they are hard on turf. Time the work for when the grass is growing strongly.

Weeds, Insects, and Disease

Healthy, dense turf is the best way to prevent problems. Integrated Pest Management (IPM) is a science-based way to manage pests. You start with prevention, you monitor what is happening, and you use a targeted treatment only when needed. Chemicals are the last resort.

Weeds

• Pre-emergent herbicides stop seeds as they sprout. Crabgrass begins to sprout when soil at a 2-inch depth reaches about 55 F, which is around the time forsythia blooms. Apply it before then.
• Post-emergent herbicides kill weeds that are already growing. Selective products target weeds but not turf. Non-selective products kill everything.

Pre-emergent products can stop grass seed too, so read the label before you overseed. Spot treat when you can, instead of spraying a whole lawn.

Common Problems

Products and the Law

The label on a pesticide is the law. Using a product in a way the label does not allow can be a federal violation. That includes rate, target, site, and protective gear. Herbicides, insecticides, and fungicides are all pesticides.

States usually require a license or certification to apply pesticides to someone else's property for pay, often under an ornamental and turf category. Unlicensed workers may have to work under a licensed applicator, or may not be allowed to apply at all. Ask before you touch a product.

Warning: Wear the protective gear listed on the label, and follow its rules for wind, rain, and re-entry. Drift can injure people and damage plants next door.

Common Mistakes

Check Your Understanding

1. A shady lawn in Ohio needs seed. Which grass suits it best, and when should you plant it?

Fine fescue suits shade. Plant it in early fall, when the soil is warm and the air is cooling.

2. Blades on a lawn are folded and blue-gray in July. What is happening?

Drought stress. It needs water, and raising the mowing height can help.

3. How much 30-0-4 fertilizer do you need to apply 1 pound of nitrogen per 1,000 square feet on 3,000 square feet?

1 divided by 0.30 gives about 3.3 pounds per 1,000 square feet. Multiply by 3 to get about 10 pounds.

4. You pull back a brown patch of turf and it rolls up like carpet. What do you check for?

Grubs. Cut a 1-foot square and count them.

Key Takeaways

• Know whether you have cool-season or warm-season grass, and which type.
• Never cut off more than one-third of the blade at a time.
• About 1 inch of water per week, in 1 or 2 deep sessions, early in the morning.
• Test soil every 2 to 3 years. Feed based on the results and the season.
• Aerate compacted soil and overseed cool-season turf in early fall.
• Follow the label and your state's licensing rules on every product.