Keeping a clean lawn free of weeds often involves regular mowing, but a new study suggests this common practice might be backfiring in the case of a particular weed.
Researchers from the University of Arkansas and the University of Texas Rio Grande Valley have recently found that frequently mowing Silverleaf Nightshade (Solanum elaeagnifolium), a weed common in many backyards, can turn it into a stronger, more resilient "superweed" (via Phys.org).
Frequent Mowing Can Turn Poisonous Weeds Into 'Superweeds'
The study, published in the journal Scientific Reports, investigated how mowing affects this invasive plant. Silverleaf Nightshade is easily identified by its purple flowers, sometimes white or light purple, and prickly spines.
Researchers led by Rupesh Kariyat and Alejandro Vasquez focused on how Silverleaf Nightshade reacts to different mowing frequencies. They observed mowed, unmowed, and frequently mowed patches of Silverleaf over several years. Their findings revealed some surprising adaptations by the weed in response to mowing.
Interesting Findings
One key change was in the flowers. Mowed Silverleaf Nightshade plants produced larger flowers, but these weighed less compared to unmowed plants.
Interestingly, even more frequent mowing resulted in even bigger and heavier flowers. This suggests that the plant is putting more resources into reproduction when it is under constant threat of mowing.
But the changes go beyond just flower size. Mowed Silverleaf Nightshade grew more spines, likely as a defense mechanism against herbivores like caterpillars.
The study also discovered that these spiny defenses were effective, as caterpillars fed on mowed Silverleaf Nightshade leaves grew significantly slower than those fed unmowed leaves. The mowed plants also developed deeper taproots, allowing them to get water and nutrients from deeper underground sources.
In a similar study from 2022, researchers discovered that shifting environmental conditions near the start of a plant's life can affect its ability to respond to changing conditions later on by altering adaptive responses.
Perhaps the most concerning adaptation is a change in seed germination. The weed seems to have developed a strategy of "staggered germination," where some seeds germinate quickly while others lie dormant for longer periods. This ensures that even if a mowing session wipes out some seedlings, others will emerge later, guaranteeing the plant's survival.
These findings raise important questions about weed management practices as other methods such as tilling the soil to remove Silverleaf Nightshade can even spread the problem due to the weed's ability to reproduce through its roots.
BERLIN, GERMANY - JUNE 15: A worker mows strips of grass in front of the Chancellery with a lawn mower on June 15, 2011 in Berlin, Germany. Photo by Sean Gallup/Getty Images
Should You Be Worried?
So, should you be worried about mowing your backyard? The answer isn't a simple yes or no. The study focused specifically on Silverleaf Nightshade, and other weeds might react differently to mowing.
"This should be something that we consider when we make management plans," says Rupesh Kariyat. "Management practices need to be better understood using the ecology and biology of the species and the other species which interact with them."
The researchers believe their findings can apply to anyone who deals with weeds, not just professional landscapers. As Alejandro Vasquez points out, "mowing is a concept the world at large can understand."
