does mowing spread weeds

Does Mowing Spread Weeds? (Tips For A Weed-Free Lawn)

In our battle against weeds, does mowing work for or against us? Mowing is an important part of a successful campaign for a weed-free lawn, but only if used correctly. Let’s see how mowing can help – or hurt – your efforts to control weed growth.

Frequent mowing helps control weeds, but it can also help them spread if done incorrectly. Clippings that contain weed seeds can spread further unless the mower’s exhaust is captured; mowers used on multiple lawns may transfer weeds. Clean the mower after use and safely discard the cuttings.

Overview of Weeds And Mowing

Looking across the smooth emerald carpet that rewards our lawn efforts, it’s jarring to see a discordant weed spoiling the scene. Neither is it satisfying to see the ragged outline of weeds resprouting in an unruly patch that was supposedly cleared.

We are sure to encounter weeds in our lawn. When it comes to plants, Nature has its own agenda, and it’s not to have a fertile field containing just one type of grass.

Grass will naturally keep weeds out once it’s well established and flourishing. Weeds don’t have a chance to prosper among tangled, interlocking grass roots and blades that block light and nutrients from stray seeds.

A thriving, weed-free lawn is the goal … but your grass needs help to achieve it.

Pulling weeds is the first defense, but it’s only effective if you get the whole root. Many weeds will grow back if even a small bit of their taproot breaks off in the soil. Pulling a single plant is useless if it’s just one of a patch of weeds with deep, interconnecting roots.

Mowing frequently at the proper grass height is a better method for combating (most) weeds in the long term. But … if mowing is part of the solution, can it be part of the problem, too?

How Mowing Can Spread Weeds

You’ve heard the nightmares and they are true. Lawnmowers can spread weeds.

There are two main ways it can happen:

  • If there is no bag to catch the cuttings, mowers can blow a ripe patch of weed seeds far and wide with the efficiency only automation can offer.
  • Seeds and weed cuttings are part of the green muck that gets stuck under a lawnmower after a cut. This material can easily fall into “clean” areas of a lawn and spread.

The first issue is easily solved by putting an exhaust-catcher bag on the mower before use. This keeps the cuttings contained until they can be safely discarded.

Note: It may be best to dispose of such clippings unless you compost it with a method that generates enough heat to kill the seeds. Otherwise expect to deal with a full, new crop of weeds anywhere you use it!

Weed contamination can be a problem if the mower is used on different lawns, especially poorly maintained properties that are essentially weed farms.

Because of this, mowing equipment used by a commercial lawn-mowing company can be a source of weed contagion. Some companies take the extra step of cleaning a mower between uses, but it isn’t standard practice.

This unsuspected spreading can happen within your own yard if you mow cleaner parts of the lawn together with areas overgrown with weeds. Watching a new crop of weeds emerge from your hard-won turf is no fun – if contamination is a potential issue, make sure the mower is cleaned between jobs.

Note: Leaving the grass clippings on the lawn can be great for building up fertility, improving texture, and lightly mulching the soil … it only becomes a problem if the clippings contain weed seeds or another spreadable contaminant. Once your lawn is relatively weed-free, you can take the bag off.

daisies in lawn

Weeds 101

Besides being unsightly, weeds aren’t good for your lawn’s health. They compete with your grass for nutrients and sunlight. Sturdy weeds often have deeper roots and more efficient absorption than your lawn’s grass. Once established, these unwanted plants can expand aggressively into their immediate vicinity and spread across your property.

Weeds are dedicated to propagation, and they’re smart. Some spread by the wind or are carried to new ground by you or your pets – or your mower. Others float and can spread themselves through runoff. Some of the more diabolical sort even shape their seeds into irresistible fairy balls to be puffed on and released to the world.

Seeds can stay dormant in the soil for years, too, just waiting for the right time to spring up and spoil the party. They often produce flowering stalks, or culms, that quickly ripen into countless seeds if not cut down in time.

Weeds can be either a cool- or warm-season species. Weeds popping up in your lawn very early in spring are usually cool-season plants that germinated the previous fall. These weeds are ready to sprout and restart their sinister cycle as soon as the weather begins to warms – rushing to get the jump on your grass.

How Mowing Can Control Weeds

Stray seeds won’t germinate and thrive if the turf is robust and well-established. A healthy, full lawn is the long-term solution to weeds, and mowing can help you get there.

There are three ways that mowing helps control weeds.

1. If done regularly, mowing cuts down weed stalks before they flower and pollinate. This keeps them from setting seed; if you eliminate the flower spikes, you eliminate the seeds.

2. Mowing kills weeds through physical attrition. After being mown down, a weed uses its resources to continue sending up new shoots and leaves … if you keep cutting them down, the weed’s reserves will eventually be exhausted and the plant will die.

Depending upon the weed, this may take more than one season. Weeds that grow close to the ground won’t be affected, but mowing is an effective way to manage sizeable species.

3. Mowing also helps reduce weeds by encouraging the grass to thicken and fill in its bare spots. Being cut triggers lateral growth: it’s part of your grass’s natural response to being grazed in the wild. This helps the grass become denser, which makes it more difficult for weeds to access the sunlight they need to grow.

One caveat is that you must keep up with your mowing schedule: if you stop mowing long enough for a weed to regrow, the plant will restore its reserves and the cycle is reset.

Though low-growing and creeping weeds have to be dealt with separately, mowing is an excellent way to control up to 60% of your weed population.

Mowing Your Way To a Weed-free Lawn

Reducing weeds requires a multi-pronged strategy that includes mowing along with healthy soil and good care. Proper mowing does more than keep the lawn looking good: it encourages denser turf and gradually eradicates larger weeds. 

To begin, make sure your mower is set to cut at the appropriate height for your particular grass species. Cut at the high end of the preferred range: being cut too close can weaken the grass and open up more space in the lawn for weeds to enter and germinate.

Another reason to cut grass as high as recommendations allow is to avoid exposing the lower levels of the lawn to more sunlight and warmth. This exposure can bring about a wave of weed growth. Keeping the grass higher blocks sunlight from the weeds and keeps the ground cooler, too.

To avoid spreading weeds when mowing, remember two things:

Bag the Clippings – Put the catcher bag on your mower when going over a weedy area.  Seeds are not the only problem: mown weeds are a collection of leaf cuttings just waiting for favorable conditions to spread.

Clean the Mower -If you mow more than one lawn, clean the green gunk out of the underside of the machine between uses. This is especially important if one of the lawns is better maintained than the other.

If part of your own lawn is out of control and staging a return to nature, avoid that area until after mowing the better parts of your yard; then clean the mower before you store it away.

Mowing on a schedule without missing sessions is the key to weed control. If you mow weekly, for example, even fast-growing weeds won’t have a chance to mature … a haphazard mowing schedule could give them time to spread.

Robot Mowers For The Win

This is where using a robot mower can be a real advantage. It offers a little extra to your anti-weed mowing campaign by making sure weeds unfailingly get regular, systematic attention.

Robot mowers can cut the lawn as frequently as the weeds require without additional effort from you. They are a great option if you find it a challenge to be as consistent with mowing as you need to be for weed control.

worx robot mower

Tips For Mowing Weeds Away

There isn’t a special skill to mowing for weed control, but there are a few tips to help the process:

  • If you plan to pull weeds, do it before mowing. It’s harder to see the weeds once they are cut short along with the surrounding grass.
  • If cool-season weeds are getting a head start on your warm-season lawn, don’t delay mowing until the grass needs a cut. Start regular mowing as soon as you see flower stalks or other signs of advancing weed growth.
  • Don’t be worried about a sudden upshoot of weed growth after you mow, which sometimes happens. As long as you mow regularly, the faster the weeds grow, the better! It will exhaust the plant sooner.
  • If the grass doesn’t need mowing but you see weeds racing ahead to tuft out or send up stalks, give the lawn a quick cut. Thwart the weed’s advantage.
  • One shortcoming of mowing for weed control is that it doesn’t reach low-growing plants. For these, hand pulling or even targeted herbicides may be needed.
  • To mow less frequently, consider cutting back on water. Both weeds and grass grow more quickly when they have more moisture.