How to recognize leafcutter bees in the garden
Look along the edge of a rose or redbud leaf. Several smooth half-circles can look as if someone used a hole punch. If you see the bee making a cut, watch what happens next. She uses her jaws to lift the piece and flies it back to a nesting tunnel.
A female can carry pollen on the hairs beneath her abdomen. Look from the side while she pauses on a blossom. The pollen may stand out more clearly than the stripes on her back. Even so, it takes more than a photo of a damaged leaf to tell which species visited.
Inside a leafcutter bee nest
Each female makes her own nest. First she finds a sheltered hollow, perhaps a hole in old wood or the open end of a stem. Then she fits pieces of leaf together inside to make a chamber. She gathers pollen and nectar, lays an egg on that food and closes the chamber. She repeats the process along the tunnel.
If you see several leafcutter bees using nearby holes, allow them room to fly. Each can tend her own young even when neighbors choose the same quiet patch. Leave an occupied stem standing so the young inside have time to develop and emerge.
Will the leaf cuts hurt my plants?
On an otherwise healthy shrub, a few cut edges are usually a cosmetic change. For example, a rose can keep flowering even after a bee has taken pieces from several leaves. There is usually no need to treat the plant. The University of California guide to leafcutting bees shows what the cuts look like.
Where to watch for pollination
Leafcutter bees visit flowers as well as foliage. For instance, watch clover or lupines for a bee moving from bloom to bloom. In agriculture, growers also use the introduced alfalfa leafcutting bee to pollinate alfalfa grown for seed. Other leafcutter species are native to North America.
Try keeping a simple field note. First record the plant you see the bee cutting. Next record the flowers she visits if you can follow her from a distance. The two plants can be different because leaves supply nesting material while flowers supply food. For more comparisons, see Utah State University’s native bee guide or explore our guide to mason bees.