How to Winterize Your Lawn in Iowa

Most Iowa lawns are Kentucky bluegrass and other cool-season grasses, and Iowa State University (ISU) Extension says they grow best in spring and in late summer and early fall. That makes fall the season when a little work pays off the most. What you do between September and the first hard freeze decides how your lawn handles snow cover, salty slush along the driveway, and the first warm days of spring.

This guide follows ISU Extension's own fall calendar. Dates are typical for Iowa; your yard may run a week or two ahead or behind depending on weather.

Your Iowa fall lawn calendar

1. Lower the mower, but keep mowing

ISU says to lower the mowing height in mid- to late September from 3–3.5 inches to 2.5–3 inches, and to never remove more than one-third of the leaf area at one time. ISU's mowing-height FAQ recommends 2.5 to 3 inches in spring and fall and 3 to 3.5 inches in June, July and August.

Don't scalp the lawn for winter. ISU warns that mowing below the recommended range can scalp the turf and weaken it, while mowing too high can cause matted grass, which encourages disease.

When to stop: keep mowing until the grass stops growing. ISU says cool-season grass foliage stops growing when daytime highs are consistently below 50°F. Its fall lawn care page says that's usually late October or early November in Iowa, and its FAQ puts it at early to mid-November in central Iowa.

2. Fertilize at the right times

ISU Extension says Iowa cool-season lawns can be fertilized in spring (April or May), mid-September, and late October/early November, and that you shouldn't fertilize Kentucky bluegrass in June, July or August. How many of those you do depends on the lawn you want:

• Minimal: one application in late October/early November.
• Moderate: mid-September and late October/early November.
• High quality: all three (spring, mid-September, late October/early November).

Each application should be about one pound of actual nitrogen per 1,000 square feet, per ISU. Read the fertilizer bag to work out how much product that is for your lawn.

Snow mold connection: ISU's snow mold page lists avoiding excessive nitrogen in the fall as one way to reduce snow mold, so stick to the recommended rate.

3. Fall is weed season (for the weeds)

ISU says late September to early November is the best time to control perennial broadleaf weeds like dandelions with broadleaf herbicides. In fall, the weeds move food from their leaves to their roots for winter, and the herbicide goes along with it. ISU notes the most effective products contain a mix of two or three herbicides, and says to carefully read and follow label directions before applying anything.

If you hire it out: in Iowa, anyone in the business of applying pesticides (which includes weed and insect control products) to someone else's property must hold a commercial pesticide applicator license from the Iowa Department of Agriculture and Land Stewardship (IDALS). Our listings show what we could verify about that license for lawn companies that offer treatments.

4. Aerate and seed (if you're early enough)

These are late-summer jobs, so if you're reading this in late October, put them on next year's calendar:

• Aeration: ISU says early September is the best time to aerate Iowa lawns. Use a core aerator (not spikes), aim for 20 to 40 holes per square foot, and aerate when soil is moist, not dry or soggy.
• Seeding: ISU says mid-August to mid-September is the best time to seed a new lawn or overseed a thin one. Warm soil speeds germination, and few weeds sprout in fall.
• Watering: ISU says turfgrass needs about one inch of water a week to keep actively growing. If you water, water deeply and infrequently.

5. Deal with leaves before snow falls

ISU warns that a heavy layer of leaves blocks light and keeps grass from making and storing food before winter, which can leave dead, weedy patches. You can rake, blow or bag leaves, or mulch-mow them: chop them fine enough to fall between the grass blades so little debris is visible. ISU says mowing works best when the layer of leaves is thin and dry, so mow often during leaf drop.

Raking leaves is also on ISU's list of ways to prevent snow mold.

6. Get ahead of snow mold

ISU Extension says gray snow mold and pink snow mold both occur in Iowa. They show up as circular, straw-colored patches when snow melts in late winter or early spring, especially after long snow cover on ground that isn't fully frozen. The damage usually isn't serious; patches typically green up, just more slowly.

ISU's prevention list:

• Avoid excessive nitrogen fertilization in the fall.
• Mow at the recommended height throughout the fall.
• Keep thatch to 1/2 inch or less.
• Rake up fallen leaves.
• Prevent heavy snow buildup on problem areas: use snow fencing and spread out large snow piles so they melt faster.

In spring, ISU suggests gently raking affected areas to help them dry out, and overseeding any that don't recover.

7. Plan where the snow (and salt) will go

Before the first storm, decide where you'll pile snow from the driveway and walk. ISU Extension says turfgrasses are susceptible to salt damage, and recommends removing snow before using any de-icer, using only enough to loosen ice, and not piling salt-laden snow around plants. If a plow company clears your driveway, talk with them about where they'll push snow. Our salt damage guide covers this in detail.

Hiring fall lawn help

If you'd rather hand off fall fertilizing, weed control, aeration or leaf cleanup, many companies that plow snow in winter also offer lawn care. Ask which services are included, how many visits, and, for any weed or insect treatment, who holds the IDALS commercial applicator license. Below are lawn companies that name Waukee on their own websites; see the towns page for other cities.

Frequently asked questions

When should I stop mowing my lawn in Iowa?

Keep mowing until the grass stops growing, which ISU says happens when daytime highs are consistently below 50°F. That's usually late October to mid-November in Iowa.

What height should I leave my grass for winter in Iowa?

ISU recommends lowering the mowing height in mid- to late September from 3–3.5 inches to 2.5–3 inches, and never removing more than one-third of the leaf blade at a time.

Should I fertilize my lawn in late fall in Iowa?

ISU lists late October/early November as one of three good times to fertilize Iowa cool-season lawns, and says a single late-fall application is enough for a minimal fertilization program. Use about one pound of actual nitrogen per 1,000 square feet.

When is the best time to kill dandelions in Iowa?

ISU says late September to early November is the best time to control perennial broadleaf weeds with broadleaf herbicides. Read and follow the label.

How do I prevent snow mold?

ISU recommends avoiding excess nitrogen in fall, mowing at the recommended height through fall, keeping thatch to 1/2 inch or less, raking leaves, and spreading out large snow piles.