Every time you mow, you face the same question: mulch the clippings back into the lawn, or bag them up and haul them away?
For St. Charles County homeowners, the answer depends on your grass type, mowing frequency, time of year, and what kind of lawn you’re aiming for. Here’s the breakdown.
Mulching returns nutrients. Grass clippings are roughly 80-85% water and contain about 4% nitrogen, 0.5% phosphorus, and 2% potassium by dry weight. By leaving clippings on the lawn, you’re effectively applying a slow-release fertilizer — returning up to 25% of your lawn’s annual nitrogen needs.
It saves time and money. You skip the bagging, hauling, and disposal. No bags to buy (St. Charles County doesn’t require bagging for yard waste collection, but many homeowners use paper bags for curbside pickup).
It’s better for the soil. Decomposing clippings feed earthworms and soil microbes. Organic matter builds up, improving moisture retention — critical during Missouri’s July and August dry spells.
Bagging prevents thatch buildup. Despite what you’ve heard, clippings themselves don’t cause thatch (thatch is made of stems, roots, and rhizomes). But excessive clippings on an already stressed lawn can smother grass.
It gives a cleaner look. If you’re selling your home or hosting an outdoor event, bagged lawns look manicured. No stray clumps or clippings tracked into the house.
Essential for weed control. If you’re mowing a lawn with active seed heads from crabgrass, dandelions, or foxtail, bagging prevents spreading those seeds.
For tall fescue (by far the most common lawn grass in St. Charles County): Mulch 90% of the time. Fescue is a bunch-type grass that benefits from the nitrogen return. Only bag when:
For zoysia and Bermuda: Mulch during active growth, bag during spring green-up and fall transition.
For Kentucky bluegrass: Mulch is fine, but bag the first mow of spring and the last mow of fall.
Regardless of which method you choose, never cut more than one-third of the grass blade at once. If your fescue is 4 inches tall, mow to no lower than 2.5-2.75 inches. Taller clippings that exceed one-third won’t break down quickly and will smother the grass beneath.
You don’t need a special “mulching mower” to mulch effectively. Any standard rotary mower can mulch if you:
Dedicated mulching mowers use a specially designed deck and blade that circulate clippings for finer cutting. They’re worth the upgrade if you mow more than half an acre.
Mulch through spring and summer (May through August). The nitrogen return helps your fescue survive Missouri’s heat stress. Only bag when you’ve missed a mow and the clippings are excessive, or when treating an active disease or weed problem.
Get the free St. Charles County Lawn Care Seasonal Checklist for month-by-month guidance on mowing, mulching, watering, and the rest of your year-round lawn plan.