Clover, with its nitrogen pulling ability, is hugely beneficial for your lawn. However, when it invades turf grasses, it spreads rampantly and chokes out the desirable grass due to its extensive root system. Additionally, clover flowers also attract pollinators like bees, which can be a problem for those with bee sting allergies.
While you can prevent clover infestation by mowing high, using a slow-release fertilizer, and addressing soil compaction issues, infestation may still be inevitable. In case clover weeds take over your lawn, the safest ways to remove them include manually uprooting the clover, using vinegar, water, and dish soap mixture, or to increase nitrogen content in the soil.
Can clover take over a lawn?
Clover can invade and take over your lawn if the conditions are right. Favorable growing conditions for this type of weed include low nitrogen levels and compacted soil. When you skip fertilizing your lawn and nitrogen levels in the soil diminish, there’s a high possibility of clover taking over the lawn.
Clover can synthesize its own nitrogen with the help of symbiotic rhizobia bacteria in its roots. This nitrogen-fixation advantage helps clover stay green and grow faster than nitrogen-deprived turf grass, eventually crowding out the grass. Note that soil nitrogen deficiency may also occur due to soil compaction; as the grassroots are unable to penetrate the soil and draw essential nitrogen.
Clover is also a perennial broadleaf weed, which means that even if it disappears from your lawn, it’ll return sometime in the spring. This weed type has better drought resilience than most turfgrasses and is also tolerant of poor soil conditions.
Clover invasion is also more likely to happen in lawns with incorrect soil pH. If your lawn soil is too acidic, turfgrass growth will slow down while clover will thrive in such conditions and eventually choke out the grass.
Finally, clover takeover on lawns may also be encouraged by a low mowing height. Whenever you mow low to reduce the mowing frequency, you’re inadvertently giving clover the upper hand; as it can tolerate low mowing while turfgrass shows signs of stress when mowed too low. Turf grass should be mowed at a high height of about 3 inches to crowd out low-growing clover.
Note: Grasses with a low-growth profile are also more vulnerable to clover infestation. Clover, though a low-growing plant itself, grows slightly taller than the grass in such turfs and prevents sunlight from reaching the grass underneath. Eventually, the clover crowds out the grass and takes over the lawn.
Ways to Kill Clover in Grass
The best ways to get rid of clover in turfgrass include the application of chemical herbicides, manual removal, and smothering. Pre-emergent and post-emergent herbicides are also a good options if you wish to kill this pesky weed while minimizing your ecological impact.
Apply a selective, post-emergent herbicide
Selective, post-emergent weed killers are able to kill clover without harming the turfgrass. Such herbicides are formulated to kill broadleaves but won’t harm grasses. A great example is Weedol Concentrated Lawn Weed-killer, which is a liquid concentrate that kills many types of broadleaf weeds and woody plants, including clover.
The active ingredient in Weedol is MCPA, a selective, post-emergence herbicide. Other selective, post-emergent herbicides that are commonly used as active ingredients in selective weed killer products are 2, 4-D, triclopyr, and quinclorac.
Take note, though, that some types of selective post-emergent are only recommended for use on established turfs, as they can stifle growth in young grass seedlings. Check the manufacturer’s product labeling for instructions..
Apply a pre-emergent herbicide
Selective post-emergent herbicides will only kill clover plants that are already growing on your turf, but not the clover seeds lying in the soil. To prevent clover seeds in the soil from germinating, apply a pre-emergent herbicide.
The best time to apply a pre-emergent herbicide is when soil temperatures are between 50 and55 degrees Fahrenheit, usually in the spring. A good example of a pre-emergent weed killer that kills broadleaves like clover is Isoxaben 75WD. This product is sold in the form of water-dispersible granules and is safe for pets.
The active ingredient in the Isoxaben 75WD is isoxaben. Other pre-emergent herbicides that are commonly used as the primary active ingredient in pre-emergence weed killer products include dithiopyr, prodiamine, and benefin. Any product that contains these compounds as the active ingredient will effectively prevent clover seeds from germinating on your lawn.
Note: Just like post-emergents, pre-emergent herbicides may be either selective or non-selective. Assuming there’s only clover seeds in the soil during the application, you shouldn’t be too worried about harming grass seed.
Remove clover plants manually
If the clover invasion is still at the early stages and only a few clover plants are visible, you can get rid of them by hand. Ensure you pull out the clover plants from the roots, or else the clover will grow back. You can use a spade to gently loosen the soil around each clover plant before uprooting.
Smother the clover
You can smother the entire lawn if you plan on killing the clover and existing grass turf, and reseeding later for new grass. To smother the clover and turf grass, cover the turf with plastic sheeting and secure the edges with stones. The plastic sheeting works by depriving the clover and the turfgrass of oxygen and sunlight. In 14 days or so, all the grass and weeds in the lawn will have been smothered to death. The grass and clover should be smothered in about 14 days.
Apply corn gluten meal
Corn gluten meal is a type of organic pre-emergent herbicide. It releases organic peptides that prevent clover seeds from germinating. Corn gluten meal is non-selective and will suppress grass seed as well. Thus, you should avoid this option if you’ve recently overseeded/reseeded your turf.
A 20-pound application of corn gluten should dry out clover seed for up to 1000 square feet of lawn area. Ensure you water the lawn immediately after application to activate this natural herbicide.
Apply vinegar solution
While you can use corn gluten meal as a pre-emergent organic herbicide, you can also use vinegar solution as a post-emergent against clover. However, apply it via spot treatment to avoid killing your desirable turf grass as well.
To make vinegar solution, mix white vinegar with water in a 1:1 ratio. Add a drop or two of dish soap to enhance the solution sticks to the clover leaves. Next, shake up the solution and use a soft cloth to apply it to the clover leaves.
Note: Spot treatment of clover is only practical for small infestations. For severe clover invasion, spray the vinegar solution over the affected areas and later on reseed the patches of turfgrass that the vinegar solution burned..
Apply a slow-release fertilizer
Some homeowners prefer to use quick-release fertilizers to make their turfs grow and fill in faster. This practice may be detrimental to your lawn as the nitrogen nutrients in the fertilizer become depleted faster. It makes the clover thrive at the expense of turfgrass in the nitrogen-deprived lawn soil.
Applying a slow-release fertilizer allows the turfgrass to recover and stay healthier in the long term. After some time, the turf grows denser and crowds out the clover. Organic fertilizers are also slow-release, with good examples being compost, manure, bone meal, and chicken litter.
Apply Roundup or glyphosate-based herbicides
Only use Roundup and other glyphosate-based herbicides as a final option where the above methods of clover eradication have failed or when an infestation is severe. Glyphosate is a powerful, non-selective herbicide that will kill all plants that it comes into contact with, including your turfgrass. Thus, this option should only be used if you’re planning to establish a new turf from scratch.
Glyphosate is a systemic herbicide that seeps into plant cells via the foliage and roots before killing the entire plant by inhibiting protein synthesis. Clover weed plants, as well as the remaining turf grass, will die within 14-21 days of glyphosate exposure.
Common examples of glyphosate-based weed killer products include Roundup Pro Concentrate (50.2% glyphosate), Eraser Weed & Grass Killer Concentrate (41% glyphosate), and Alligare Glyphosate 5.4 Herbicide (53.8% glyphosate).
Note: Glufosinate-based herbicides are a less-powerful alternative to glyphosate-based products. They are contact herbicides that only kill the parts of the clover they come into contact with. On the bright side, though, they have an ecological advantage over glyphosate as the active ingredient (glufosinate) is broken down quicker in the soil by bacteria, leaving no residue.
What kills clover but not grass?
Selective herbicides that are known to kill broadleaves like clover without harming turfgrass include MCPA, quinclorac, triclopyr, isoxaben, clopyralid, and 2,4-D.
i. MCPA– a systemic weed killer used to control several types of broadleaf weeds, both perennials, and annuals. Common commercial herbicides containing MCPA include Agroxone 50 Weed Killer and Chiptox Sodium Salt herbicide.
ii. Quinclorac– though more commonly used on annual grassy weeds such as crabgrass, quinclorac will also kill clover without harming turf grass. Common quinclorac herbicide products include Quinclorac 75 DF and Prime Source Triad QC Select.
Iii. Triclopyr– a synthetic, selective herbicide that kills several species of woody plants and broadleaves such as clover. Herbicide products with triclopyr as the primary active ingredient include Altix 240 EC and Nomix Enviro Garlon Ultra.
iv. Isoxaben– a selective herbicide that can be used both as a pre-emergent and as a post-emergent herbicide against broadleaves, including clover.
v. Clopyralid– a selective post-emergent used on broadleaf weeds; poses minimal toxicity risk to humans and other mammals.
vi. 2,4-D– a selective, post-emergent weed killer that kills broadleaf weeds by disrupting cell growth processes. Popular 2,4-D herbicide products include Trimec Lawn Weed Killer and Endrun Turf Herbicide
i. Michelle Wiesbrook, University of Illinois Extension: Using Vinegar as a Herbicide
ii. National Pesticide Information Center (NPIC): Glyphosate- General Fact Sheet