Frequent Mowing May Transform Poisonous Weeds Into ‘Superweeds’

Frequent mowing in pursuit of a tidy lawn or garden can create stronger, more resilient toxic superweeds

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Silverleaf Nightshade (Solanum elaeagnifolium) has populations in both North and South America. (Credit: Dick Culbert / CC BY 2.0)

Keeping a lawn or garden tidy and free of weeds often involves regular mowing, but a new study suggests this common practice might be causing more problems than it solves with regards to one particular weed. A new study reports that frequent mowing of a common backyard weed, Silverleaf Nightshade, Solanum elaeagnifolium, can transform it into a resilient “superweed” that is more difficult to control.

Silverleaf Nightshade is easily identified from its purple flowers, which sometimes are white or violet, and its prickly spines. It is a New World plant that may have originated in North America before being accidentally introduced to South America or in the opposite direction. It is found from Kansas to Louisiana, down through Mexico, and further south into Uruguay, Argentina, and Chile. It is invasive, also being found in South Africa and in Greece where it infests fields and slurps up valuable nutrients intended to support the growth of cash crops. In return for the windfall, this plant grows poisonous berries and flowers, and prickly spines.

Silverleaf Nightshade has several close relatives that also produce toxic berries but some of its relatives include friendly plants such as tomatoes, peppers, potatoes, and eggplants.

Considering the toxic nature of Silverleaf Nightshade, it would seem prudent to prevent it from growing and spreading.

To that end, a team of researchers from the University of Arkansas and the University of Texas Rio Grande Valley investigated how Silverleaf Nightshade reacts to different mowing frequencies. They observed mowed, unmowed, and frequently mowed patches of these plants over several years in and around Edinburg, Texas (Figure 1).

F I G U R E 1 : Geographic map of field collection sites (A) of Solanum elaeagnifolium flowers in Hidalgo County, Texas, USA, and their coordinates (B). Unmowed and mowed areas were annotated by squares or stars respectively. Map from Google Maps, 2024, Map of Hidalgo County (Google Maps, Google, Mountain View, California, USA). The locations were added to the map using Microsoft Paint 11.2309. (doi:10.1038/s41598–024–58672-w)

Senior author of the study, Rupesh Kariyat, who now is an associate professor of entomology and plant pathology at the University of Arkansas and director of the Arkansas Agricultural Experiment…