Can you just mow over weeds?

Table of Contents

Quick Answer

You can mow over weeds, but it may not always be the most effective way to control them. Mowing can temporarily reduce weed growth, but it does not kill the roots so weeds often grow back quickly. Using proper mowing technique, at the right height and frequency, can help discourage weeds. But for best control, using herbicides or manual removal may be needed in addition to mowing.

Mowing Height for Weed Control

Mowing height can impact weed growth. Keeping your lawn slightly taller, around 3-4 inches, can help reduce weed germination and growth. This is because:

Taller grass shades the soil, reducing light reaching weed seeds needed to germinate.

Thicker turfgrass crowds out space for weeds.
Taller mowing height reduces grass stress, increasing its competitiveness with weeds.

Mowing too short causes thin turfgrass growth, allowing more light to reach the soil surface which favors weed germination. It also stresses the desired grass, reducing its competitiveness with weeds.

Recommended Mowing Heights for Common Grass Types:

Grass Type	Mowing Height
Kentucky Bluegrass	2.5-4 inches
Perennial Ryegrass	2-3.5 inches
Tall Fescue	3-4 inches
Bermudagrass	1-2 inches
Zoysiagrass	2-3 inches

Adjust mowing height based on grass type and conditions. Mow at the highest recommended height for your grass to discourage weeds. Raise it even taller if the turf is stressed by drought, disease, or heavy traffic.

Mowing Frequency and Weed Control

In addition to height, mowing frequency also impacts weeds. Here are some tips:

Mow often enough that no more than 1/3 of the grass blade is removed each time.

This prevents scalping the turf and undue stress.
Grass types like Kentucky bluegrass may need mowed 3 times per week at peak growth.
For optimal turf health and density, mow at the frequency needed for your grass type and conditions.

Infrequent mowing allows excessive growth which shades and crowds out low-growing weeds.
But less frequent mowing risks scalping, thinning, and stressing the turf which can increase weeds.

Get to know your lawn’s optimal mowing height and frequency. Maintain proper mowing practices to encourage thick, healthy grass that resists weeds. Adjust mowing as needed to account for variations in growth rate through the seasons.

Does Mowing Actually Kill Weeds?

Mowing alone does not kill weeds or stop them from growing back. It only temporarily cuts off the weed stems and leaves. The root system remains intact underground, allowing the weeds to quickly regrow.

Some tips on mowing and weeds:

Do not let weeds go to seed. Mow to prevent seed production.

Certain weeds like dandelions will still go to seed even if cut by mowing.
For low-growing broadleaf weeds, mowing acts like pruning to encourage denser growth.
Never mow weeds after herbicide treatment. This reduces effectiveness.

Bag clippings from large weed infestations to prevent spread.
Clean under deck after mowing weedy areas to prevent seed spread.

While mowing removes visible weed growth for a short time, the roots remain alive and weeds will return. For most weeds, additional control methods are needed along with proper mowing technique.

Improving Weed Control when Mowing

Beyond just mowing, certain practices can enhance weed control:

Maintain sharp mower blades. This creates clean cuts that discourage regrowth.
Avoid mowing when weeds are wet. This prevents spreading seeds.

Use mulching or bagging attachments. Mulching leaves cut weeds on the lawn to dry out. Bagging removes clippings.
Adjust mowing patterns. Change direction each mow to prevent ruts and compacted soil.
Fill in bare spots. Weeds thrive in thin and bare areas. Overseed to choke out weeds.

Proper mowing technique creates turfgrass conditions that better compete with weeds. But mowing alone is not enough for most weed problems. Integrate other controls like herbicides, hand weeding, or soil improvements to boost weed management.

When Mowing Worsens Weed Problems

Certain mowing mistakes can make weed problems worse:

Mowing too low causes turf thinning and invites weeds.

Infrequent mowing allows weeds to go to seed.
Dull mower blades create ragged cuts that stress grass.
Mowing wet weeds spreads seeds and stems that root in soil.

Tall grass mown after herbicide application reduces chemical contact.
Failure to clean mowers spreads weeds from infested areas.
Compacted soil and ruts from repeated passes foster weeds.

Correct poor mowing practices that worsen weed growth. Keep mower blades sharp, mow at recommended heights for your turfgrass, and mow frequently enough to prevent scalping. Mowing properly will not control most weeds, but it makes your lawn less inviting to them.

When to Mow Weeds

Timing matters when mowing weeds:

Avoid mowing weeds after rain or irrigation. Let the foliage dry out to prevent spreading seeds and stems.

Mow cooler season annual weeds in late spring. This reaches them at a smaller growth stage for better control.
Mow perennial weeds repeatedly early in the season. Cutting off top growth repeatedly depletes root reserves.
Mow before weed flowers open. Prevent the production and spread of seeds.

Mow weeds separately from lawn mowing whenever possible. This avoids spreading seeds and stems between areas.

Timing mowing strategically based on weed growth cycles and seed production can improve control. Target small annual weeds early before they establish, and repeatedly mow out perennial weeds to drain their root systems.

When to Avoid Mowing Weeds

In some cases, holding off on mowing weeds is recommended:

Avoid mowing weeds after herbicide use. Mowing reduces contact and effectiveness.
Hold off if weed seeds are present. Mowing spreads seeds and propagates infestation.
Do not mow drought-stressed weeds. Let them desiccate and die to avoid regrowth when water returns.

Avoid mowing weeds during high pollen seasons. Prevents spreading allergy-triggering particles.
Delay mowing if weed stems are prone to regrowth from cuttings. Mowing would increase stem rooting and growth.

Sometimes withholding mowing avoids worsening the weed problem. Let weed growth desiccate and die back during droughts, or after herbicide treatment. Avoid mowing weeds with seed heads or that spread from cut stems.

Best Practices for Mowing Weeds

Follow these tips for optimal weed mowing practices:

Mow weed-infested areas last to prevent moving seeds and stems.
Clean the mower deck and undercarriage after mowing weeds.

Use bagging attachments to remove weed clippings.
Adjust mower height to recommended settings for your grass type.
Sharpen mower blades regularly for clean cuts.

Alter mowing patterns in different directions.
Mow weeds separately before they reach full seed production.
Time mowing to cut annual weeds early in establishment.

Mow repeatedly to gradually drain perennial weed root systems.

Proper practices reduce weed spread, prevent seed production, and stress growth. But also use additional control methods like herbicides, cultivation, or smothering for more effective and lasting weed management.

Limits of Mowing for Weed Control

While mowing can help reduce weed problems, its effectiveness has limits:

Mowing does not kill weeds or fully prevent regrowth.
It must be repeated frequently to suppress growth.
Low-growing weeds escape being cut by mower blades.

Some weeds spread or regenerate from cut stems.
Mowing can disperse seeds of weeds if timed improperly.
Adjusting mower height to deter weeds may compromise desired turfgrass.

Frequent mowing is labor intensive and uses fossil fuels.

For most lawn weeds, mowing alone provides temporary cosmetic suppression but does not provide lasting control. Integrate supplementary practices like soil improvements, proper fertilization, herbicide use, and manual weed removal for the best control results.

Weeds That Are Hard to Mow Down

Several common weeds prove difficult to control by mowing alone:

Dandelions

Low rosettes escape mower blades.
Taproots are deep and unaffected by cutting.

Plants readily regenerate from severed leaves and crowns.

Creeping Charlie

Low growth habit evades mower blades.

Can root where creeping stems contact soil.
Spreads rapidly by seed and stem fragments.

Wild violets

Leaves stay below mowing height.
Spread aggressively by rhizomes and seeds.
Regenerate from cut leaves and stems.

White clover

Low-growing leaves hide under grass blades.
Taproot is unharmed by mowing.

Spreads prolifically by aboveground stolons.

For low-growing, spreading weeds like these, mowing provides little control. Target them with selective herbicides, hand removal, smothering, or cultivation for better suppression.

Weeds That Can Be Managed by Mowing

Some weeds can be partially managed with proper mowing technique:

Crabgrass

Mowing regularly at recommended turf height helps compete with growth.
Cutting plants too low stresses desired grass.

Time summer mowing to prevent seed production.

Broadleaf plantain

Maintaining dense lawn cover crowds out growth.

Cutting leaves near the crown injures the plant.
Prevents vertical growth and seedhead formation.

Spotted spurge

Frequent mowing stresses root system.
Cutting stems near the crown can suppress regrowth.
Prevents flowering and seed spread.

For weeds with upright growth that rise into mower range, diligent mowing can help reduce spread and weaken plants. But combination with other controls is still needed for full suppression.

The Bottom Line

Mowing alone does not provide sufficient control for most lawn weeds. But proper mowing practices are an important part of an integrated weed management plan. Mow at heights and intervals ideal for your turfgrass to encourage dense, vigorous growth that competes with weeds. Time mowing to prevent weed seeds and reduce growth. Adjust mowing patterns and equipment to avoid spreading weeds. Combine mowing with other manual and chemical controls for optimal, lasting weed suppression.