Beneficial Weeds – How Does White Clover Nitrogen-Fixation Benefit Grass

By Laura Miller | March 28, 2021
Image by Mark R Coons
by Laura Miller
March 28, 2021

Recent estimates indicate the average United States household spends over $500 annually on lawn care and gardening activities. This includes cutting the grass, trimming trees, and of course, ridding our lawns of weeds. Since World War II, the concept of a weed-free lawn has fueled the multi-billion dollar lawncare industry. Yet the question remains: Can weeds be beneficial?

What Are Beneficial Weeds

If you walk through my lawn, you will see weeds. What exactly is a weed? Often, what we call weeds are nothing more than native plants growing in the wrong place. By wrong place, I mean places where we don’t want native plants to grow. Mother Nature obviously has a different plan.

I bow to her wisdom and in lieu of chemical sprays; I prefer a more natural approach to lawn care. I cut the grass on the highest setting of my lawn mower, which aids in promoting a thick turf with deep roots. When necessary, I catch the clippings to prevent the dispersal of weed seeds. Most importantly, I encourage the growth of white clover “weeds.”

When we ask, “Can weeds be beneficial,” the answer is yes. When it comes to white clover, Mother Nature has provided us with the perfect solution for worry-free lawn fertilization. Like many legumes, white clover nitrogen fixation allows these beneficial weeds to pull nitrogen from the atmosphere and make it available for its neighboring turf grass plants to utilize. 

In fact, prior to World War II, white clover was a key component of lawn seed mixes. In addition to its nitrogen-fixation ability, these “weeds” are relatively drought-resistant. White clover weeds have a mature height of less than 6 inches (15 cm.). This corresponds nicely to the growth rate and recommended cutting height for most turf grass. 

White Clover Nitrogen Fixation 

In its simplest terms, white clover nitrogen fixation is the result of a symbiotic relationship between a legume plant and the Rhizobium spp. bacteria. Photosynthesis by the host plant provides the energy the bacteria needs to convert atmospheric nitrogen (N2) to ammonia (NH3). The latter being a form of nitrogen the white clover plant can utilize.

Like other legumes, white clover stores excess nitrogen in small nodules on their roots. In order for these beneficial weeds to release the nitrogen into the soil, the root or part of the root must die. While this may leave us scratching our heads as to how white clover can benefit lawn turf, the answer is quite simple.

Each time I mow my grass, I also cut back the white clover. Doing so results in the death of a small portion of the root. So basically, when I cut my grass, small amounts of nitrogen are released into the soil.  

This slow stream of nitrogen not only nourishes my turf grass, but it also has an added benefit. Since there’s no need to apply fertilizer or weed killer to the turf, I can have a luscious green lawn without the worry of environmental issues associated with chemical runoff. So whenever I see beneficial weeds growing in my lawn, I don’t reach for the weed killer. I smile instead.

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  • Bubba
    Comment added April 3, 2021Reply

    Yet another article on the “benefits” of leaving weeds in your lawn? I think this is just another load of fertilizer. Put your weedy lawn next to one managed by a professional lawn service and yours will be seen for what it is. Let me guess, you collect rainwater and have 3+ cats? Why does everyone need to do as you do? My beautiful lawn isn’t contributing to your weedy, “organically” fertilized creation. Yet I don’t feel the need to speak to you. Learn to live and let live. Your choice isn’t mine and mine isn’t yours.

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