Are Weeds Actually Bad For Your Lawn?

Whether you view weeds as beneficial or problematic depends on your perspective and the goals you set for your lawn. Many gardeners embrace biodiversity in turf areas to support pollinators, birds, and other wildlife while reducing the inputs needed for lawn maintenance. Other homeowners are not ready to turn their lawns over to weeds, even beneficial ones.

Whether your lawn goals include building natural diversity or maintaining a more traditional aesthetic, rethinking your approach to weeds and focusing on lawn health can save you time and money while protecting the environment.

Americans spend billions of dollars and countless hours managing pristine, weed-free lawns surrounding their homes. The modern approach to lawn care requires large inputs of chemicals, water, fuel, and labor. But lawn care has not always looked the way it does today and the broadleaf plants growing in lawns have not always been viewed as weeds. Lessons from earlier lawn management practices tell us our approach to weeds doesn’t have to be all or nothing. Maintaining a healthy and diverse lawn is a balancing act. One that can benefit the environment and meet our aesthetic goals. 

Beneficial Lawn Weeds

For decades, a pristine, weed-free lawn has served as the gold standard of the American landscape, but not all weeds are bad. Learning the benefits and challenges of different weed species is a good place to start when it comes to determining the need for management.

Many plants that we consider lawn weeds provide valuable environmental services. Like their grass companions, broadleaf weeds work to control erosion and sequester carbon. They also help shade the soil, keeping it cooler than grass alone, which prevents it from drying out so quickly and thus reduces irrigation needs.

Clover and other legumes (plants in the pea family) naturally fix atmospheric nitrogen, making it available to turfgrasses and replacing the need to apply fertilizers. In fact, the earliest lawn seed mixes brought to America included clover. It was not until the advent of broadleaf herbicides in
the 1950’s that clover came to be considered a weed, as these chemicals do not discriminate between beneficial “weeds” like clover and other, more problematic plants.   

Flowering lawn weeds like clover and self-heal provide a rich source of nectar for beneficial insects, including pollinators. Many lawn weeds serve as host to developing larvae of butterflies, moths, and other insects. These in turn support thriving bird populations. Lawns cover an estimated 40 million acres in the United States. That’s a lot of potential pollinator habitat that can be managed to include at least some beneficial weeds.

Gardeners seeking to increase the biodiversity of lawns might consider allowing weeds with certain traits to remain. Plants that tolerate mowing and still produce flowers will perform well in lawns while maintaining a desirable appearance. Plants that support pollinators also make good selections.

Beneficial weeds for Southern lawns include:

• White clover, Trifolium repens
• Frog fruit, Phyla nodiflora
• Self heal, Prunella vulgaris ssp. lanceolata
• Blue-eyed grass, Sisyrinchium angustifolia
• Saltmarsh (lawn) aster, Symphyotrichum divaricatum
• Lyre-leaf sage, Salvia lyrata
• Florida betony, Stachys floridana
• Yellow wood sorrel, Oxalis corniculate
• Blue violet, Viola sororia

Problematic Lawn Weeds

Not all lawn weeds fit within the biodiversity model. Some plants are simply problematic. There are weeds like nutsedge (Cyperus spp.) and West Indian chickweed (Drymaria cordata) that reproduce and spread quickly, competing with turfgrasses for nutrients, water, and sunlight. Such weeds crowd out turfgrasses and lead to patchy, unhealthy lawns. Other weeds simply detract from the visual or functional aspects of the lawn. Invasive species such as lesser celandine (Ficaria verna) and Japanese knotweed (Fallopia japonica) can also take hold in lawns and spread to nearby natural environments.  

These weeds require control to prevent upsetting the entire turf ecosystem. However, how we manage lawn weeds can be equally problematic. Conventional lawn service treatments typically carpet the entire lawn with pre-emergent herbicides to prevent lawn weeds. These products kill both beneficial weeds like clover along with the more problematic ones. Post-emergent herbicides can be used more selectively, but also pose environmental risks, including toxicity to birds, bees, and mammals that consume or contact them.  

A safer, more cost-effective approach to managing weeds is through maintaining healthy, vigorous lawns. This approach works for both traditional lawns and biodiverse lawns. 

Manage Lawn Weeds through Cultural Practices

Healthy, vigorous lawns are more resilient to weeds, drought, and insect and disease pests. You can promote a lush, dense lawn through regular and timely mowing, irrigation, and fertilization.  

Regardless of your lawn goals, it is best to start with healthy soil. Many weed problems begin because lawn grasses are stressed due to nutrient deficiencies. Conduct a soil test to determine soil pH and nutrition needs. Address any nutrient deficiencies by applying a slow-release fertilizer according to soil test results.

Take care not to over-fertilize the lawn. Fertilizer runoff from lawns is a major source of nutrient pollution in lakes and streams. Over fertilized lawns also require more water to maintain. Remember that lawns containing clover may not require supplemental fertilization thanks to the nitrogen-fixing properties of clover plants. Base any fertilizer applications on the results of soil tests.  

Taller turf stands tend to compete better against weeds and are more resilient to drought and other stresses. Apply the rule of one-third to establish your mowing routine. This rule tells us to never cut more than one-third of the grass height in a single mowing session. By following this rule, the height at which we maintain our lawn impacts how often we need to mow. In general, the taller you maintain your lawn, the less often you will need to mow.  

Water the lawn deeply only when needed to encourage plant health and combat weeds. Deep irrigation encourages deeper root growth and saves you water. Allow the top two inches of soil to dry between watering, which helps discourage water-hungry weeds like sedges. Sometimes, simply reducing irrigation frequency is enough to combat weed problems associated with excess soil moisture.  

A dense, healthy lawn out competes most grassy annual and perennial weeds as well as many broadleaf perennials. Of course, some weeds are inevitable. Hand removal is the safest method of weed management when protecting pollinators is a concern. Perennial weeds require deep digging to remove the complete root system. Hand removal is intensive but ensures only target species are impacted. Another option is to spot spray targeted weeds. Weeds are easiest to manage when plants are young. Monitor the lawn regularly to identify and treat weed infestations early. 

Weeds often take advantage of disturbances to invade lawns. Areas where the lawn is thin are most likely to sprout weeds. Overseed thin lawns and bare patches as needed to reestablish a dense turf cover. Bare patches are often left behind after removing large patches of weeds. These benefit from a sprinkling of grass seed to fill the gap. In cool season lawns, overseeding is part of the regular maintenance program to keep weeds out and promote a lush, beautiful lawn. 

Whether or not you decide to allow some beneficial weeds to flourish or strive to maintain a largely weed-free lawn is a matter of personal choice. Understanding the pros and cons associated with
different weed species and management strategies will help you develop a weed control plan for your lawn. And maintaining turf health, regardless of management style, is your best defense against weeds.