White clover is an important food source for honeybees. Photo by Adobe Stock

This past year has been a year of firsts for me in Louisiana. Specifically, it is my first time experiencing each season in full and observing how turfgrasses and weed populations are affected by the changing of each season. One observation I made this spring was just how well we can grow white clover (Trifolium repens) in Louisiana, which I will refer to as clover for this article.

A few things must be discussed before we dive into controlling clover in your lawn. White clover can be a very polarizing topic in the green industry. It’s one of those plants that, like bermudagrass, can be either desirable or a nuisance, depending on the specific situation. Bermudagrass is desirable in Tiger Stadium on a Saturday night in the fall but not so much in our gardens and flower beds. A similar contrast exists with clover; clumps of clover can be undesirable, disrupting the uniform appearance of a well-manicured lawn. Additionally, too much clover can make a property look unkempt or unsightly. On the other hand, the abundantly produced small, white flowers provide nectar and pollen, essential food sources for various pollinators. We’ve all seen honeybees on clover, traveling from flower to flower on spring days. White clover also has a long blooming period, which makes it an important food source during the months when many other pollinator forage plants aren’t blooming. I’m not here to tell you to stop controlling the clover in your lawn. Instead, it’s my duty to provide you with the information necessary to make that decision for yourself. With that out of the way, let’s discuss control options.

Control Clover with Healthy Grass

Some things in the turfgrass/lawn industry will continue to be emphasized until the end of time or until we stop growing turfgrass altogether. One example of this is that the absolute best defense against weeds is a healthy, dense stand of turfgrass. Weeds don’t cause weak grass; weak grass is the cause of weed infestations. So how do we achieve a resilient, thick stand of grass? Focus on what you can control: grass species, mowing height and frequency, blade sharpness, fertility and water (somewhat controllable). These can be summed up quickly:

Plant proper species. Consider soil pH, shade and your ability to irrigate.

Mow at the recommended height. Grasses do best when not mowed too low or too high.

Adopt a growth-based mowing schedule vs. a calendar-based schedule. Just mowing once per week may not be frequent enough to avoid scalping turfgrasses that grow quickly during the warm season. You’d be surprised how much focusing on frequent mowing will improve the quality of your lawn. From observation and anecdotal evidence, the lawns I see with the most weeds are also the lawns I see getting mowed about once a month, with the mower set as low as it will go. This sort of mowing practice is not conducive to healthy turf.

Keep mower blades sharp. Wounds from sharp blades heal faster than those created with dull mower blades. Even just buying a new blade once a year won’t break the bank.

Provide proper fertility, specifically nitrogen fertilization. Clover can utilize atmospheric nitrogen that your lawn does not have access to and will out-compete your turf in infertile soil. Take care not to be heavy-handed with the nitrogen if you have centipedegrass (Eremochloa ophiuroides); it prefers much less fertility than other turfgrasses.

Provide about 1 inch of water per week (including rainfall). Overwatering leads to disease and poorly oxygenated soil, and droughty turf will be at a disadvantage.

Clover Identification and Timing

Next, we need to consider the lifecycle of clover. Clover is a perennial weed that can return year after year from the same plant. This is different from annual weeds, like crabgrass, that are established from newly germinated seeds every year. When controlling annual weeds, preemergence herbicides can be particularly effective. The weed seed germinates, immediately brings in herbicide, and control hopefully occurs without even noticing the weed was there. Some of these herbicides may work for controlling clover that is trying to establish from seed for the first time. However, previously established clover will not be affected by these products, meaning we must investigate postemergence herbicides for proper white clover control. But we don’t just want to pick a postemergence herbicide labeled for clover control and call it a day. We want to maximize the efficacy and efficiency of our herbicide application. This results in better long-term control and fewer trips to the store to spend our hard-earned money on weed killer.

Again, when it comes to maximizing clover control, we need to consider what we have control over and exercise that control to the best of our ability. This means properly identifying white clover, applying the product when clover is most easily controlled and choosing an efficacious product when control is deemed necessary.

I won’t discuss the morphological characteristics of white clover. Remember that there are look-alikes, such as yellow woodsorrel (Oxalis stricta) and black medic (Medicago lupulina). If the plant you’re spraying isn’t white clover, you may not get the results you were hoping for. Proper weed identification is paramount.

Another critical aspect of postemergence weed control is to remember that, within weed species, a younger, less developed weed is an easier weed to control than a well-established, mature weed. The earlier you can control the weed, the more success you will find. White clover is a cool-season perennial. Clover will wait out the sweltering Louisiana summers in a dormant state until soil temperatures cool in the fall and proper conditions for growth begin again. This means as soon as you see clover in the fall, it’s time to spray.

The idea is to hit the clover at its weakest time, either right after exiting dormancy or right as it begins entering dormancy in the late spring. Plants exiting dormancy are often less vigorous and hardy and are more easily compromised. Another good time to apply herbicide could potentially be in the spring as clover is entering its dormant state. However, this could coincide with the green-up of your lawn as it begins exiting dormancy. Herbicide injury is often observed when herbicides are applied during the lawn’s spring green-up period. This makes fall, or as soon as you see clover again once the weather cools, the safest time for control. If you do find clover has persisted throughout the winter and into the late spring, and you’re confident your lawn has had time to exit dormancy and resume growth, a springtime application can be safely made.

We know what class of products to buy and when to spray them; now, we need to examine specific active ingredients. Luckily, plenty of herbicide-active ingredients effectively control white clover when appropriately applied following the label directions (Table 1).

Table 1. Herbicide active ingredients used for control of white clover (Trifolium repens) and their safety on various commonly-planted lawn grasses in Louisiana.

Left: Yellow woodsorrel, left, and white clover look similar, but yellow woodsorrel has lobed or heart-shaped leaves and yellow flowers. Photos by Eric DeBoer. Right: Dull mower blades result in frayed grass blades that take longer to heal. Photo by Bob Mugas, University of Minnesota.

Be careful spraying atrazine near bodies of water or on sandy soils that are easily leached. Stay away from the bases of your trees with atrazine and metsulfuron. You’ll find a few different products at the home improvement store containing various mixtures of 2,4-D, mecoprop (mcpp) and dicamba. Use caution and reduced rates when spraying 2,4-D on centipedegrass and St. Augustinegrass. However, if the label states it is safe, applying 2,4-D-containing products to either grass shouldn’t be an issue. Quinclorac is an active ingredient typically used for crabgrass control, but this also has activity on clover. If you’re not purchasing a ready-to-use product and mixing the herbicide yourself, check the label for instructions regarding the use of nonionic surfactants or methylated seed oil. These can greatly increase herbicide efficacy.

Following all the previous steps will help you in your battle against clover infestation. Don’t forget that clover can be an important food source for pollinators during the late winter and early spring. Hey, maybe a little bit of clover isn’t so bad after all.