In March 2018, researchers published a new study about the effects of lawn mowing frequency on bee populations in urban yards. Yards in the study were mowed at 1-, 2-, or 3-week intervals throughout the growing season. Before the yards were mowed, the number of dandelions, clovers, and other flowers growing wild in the yard were counted. Surveys were also conducted to determine the bee populations for each yard. The yards were then mowed to a height of 2.5 inches. No fertilizers or irrigation were applied to the yards during the two year study period.
The study found that yards mowed every 3 weeks had more flowers than yards mowed more frequently. However, yards mowed every 2 weeks had more bees than yards mowed either every week or every 3 weeks. The researchers suggested several possibilities for this surprising finding. One hypothesis is that the taller grass in the yards mowed every 3 weeks made it harder for the bees to get at the more abundant flowers. A second hypothesis is that the more abundant flowers in the yards mowed every 3 weeks made the traps less attractive to the bees, thus making it look like there were fewer bees even though that might not be the case. A third hypothesis is that cutting the grass from an average of 6 inches after 3 weeks of growth down to only 2.5 inches may have been too drastic of a change. It may have basically created a feast or famine regime for many of the small, native bee species with short foraging distances. Other hypothesis that could explain the surprising difference between bee abundance in yards mowed every 2 weeks compared to every 3 weeks were also discussed.
The researchers recognize that more research needs to be conducted on this topic and in many more locations. Like most good research projects, this one resulted in more questions than answers. However, at least one thing seems apparent from this study – mowing your yard every week is not good for bees. Even just reducing your mowing to every other week can help bee populations. This doesn’t even take into account the benefits to butterflies, songbirds, or other wildlife that might use your yard. I know just from personal observation from when we lived in town that we always had more birds foraging through our grass than our neighbors who kept their grass several inches shorter than ours. So if you want to do something super easy that requires absolutely no effort on your part to help pollinators, mow your yard less frequently and let your yard weeds bloom.
This article was part of Shannon’s original Kentucky Pollinators and Backyard Wildlife blog which evolved into the blog for Backyard Ecology.
Backyard Ecology: Exploring Nature in Your Backyard
Nature isn’t just “out there.” It’s all around us, including right outside our doors. Hi, my name is Shannon Trimboli, and I am the host of Backyard Ecology. I live in southcentral Kentucky and am a wildlife biologist, educator, author, beekeeper, and owner of a nursery specializing in plants for pollinators and wildlife conservation. I invite you to join me as we ignite our curiosity and natural wonder, explore our yards and communities, and improve our local pollinator and wildlife habitat. Learn more or subscribe to my email list at www.backyardecology.net.