The more diverse a farm’s plant population, the more beneficial it is for bee pollinators, and the more efficiently those pollinators work.
Those are the conclusions in a new paper published in the journal Ecology Letters by former Washington State University graduate student Elias Bloom.
Bloom and his co-authors, WSU entomology professors Tobin Northfield and David Crowder, looked at pollinator and plant populations on small farms (under 30 acres) and urban gardens in western Washington.
“Growing a wide variety of plants boosted the number of bee visits,” said Bloom, now a post-doctoral research associate in Michigan State University’s entomology department. “People want a silver bullet crop that they can plant that will bring in more pollinators, but that idea just wasn’t supported by our data. Having a variety, especially if they’re rare in a region, is the best way to increase pollinators.”
These rare plants, which could be anything that isn’t grown by other nearby farms, complement more traditional crops because they may flower at different times of year, or have beneficial traits that help pollinators vary their nutritional intake, he said.
Increasing that diversity also boosts pollinator efficiency by upping the number of visits a bee makes to crops at that farm.
“That means farmers can increase bee visits to their farm without adding more bees,” said Bloom, who earned his Ph.D. from WSU in entomology in 2019. “And we showed it works for both honey bees and wild pollinators. If a farmer is thinking about buying more bees, planting more diverse crops could be an alternative.”
A third finding of the paper is that giving bees a diversity of resources, like nesting habitat and flowers, in landscapes around a farm can also increase pollinator visits to a farm.
Bloom and his colleagues worked closely with 36 farms and urban gardens to look at the variety of plants each produces, and to measure pollinator visits. Among their partners were Hmong gardeners, originally from Southeast Asia, who now farm in the Seattle area.
“They brought a few plants with them when they immigrated here that you won’t find in other gardens,” Bloom said. “But they also grow staples found on most farms and gardens nearby, like tomatoes, peppers, or squash. Our research shows that this experimentation to introduce rare plant species may drive plant-pollinator interactions.”
That doesn’t mean farmers have to seek out rare produce from Asia or Africa, it just means they should consider a wider variety of plants from different plant families.
“You ideally want plants that flower at different times and with different flowers shapes and dimensions,” Bloom said. “Some flowers are very small and shallow, which is great for small wild bees. Taking those things into consideration helps boost pollinator visits to your farm or garden.”
Bloom’s research was part of his Ph.D. dissertation and was funded in part by the National Science Foundation, the USDA, Western Sustainable Agriculture Research and Education, and others.