Researchers found that before flowers were open, bees without other food sources started making small holes in plant leaves. Rather than eating the leaves, the insects did this so the flowers would bloom up to 30 days ahead of schedule. Initially, researchers at ETH Zürich, a public research university in Zürich, Switzerland, made the discovery by accident. They were observing how bees respond to different smells but began noticing tiny holes in the leaves of the plants in their study. At first, they thought the bees might be feeding on the leaves themselves, but the insects weren’t taking any pieces back to their colony or biting any leaf enough to get much food from it. Previously, scientists had found that lightly damaging plants can speed up the flowering process. Sometimes when plants in nature are stressed (such as by drought or plant disease), they’ll flower faster. That helps them produce seeds quicker and increases their chances of surviving. But until now, bees and other pollinators have never been known to intentionally speed up the blooming process to gain access to pollen and nectar sooner. To figure out what was happening, the scientists put hungry bees that hadn’t had any pollen in three days in mesh bags with 10 black mustard plants. The bees munched at least five holes in each plant, and, on average, the black mustard flowered 17 days later. Plants grown under similar conditions that weren’t nibbled on by the bees took an average of 33 days to flower. Researchers conducted a similar experiment with tomato plants and found that they bloomed up to 30 days early. The scientists also noted that bees that were hungrier and hadn’t had pollen in a few days cut more holes in the foliage than bees that were well-fed. However, they found that just damaging the leaves of a plant doesn’t speed up flowering as much as the bees’ method. When researchers cut holes in the plant leaves, the plants flowered quicker but not as quickly as the bees had nipped. This raises the possibility that there’s something in the bees’ saliva that helps speed up flowering even more than damaging the plant. The scientists also saw two wild bee species chewing holes in leaves outside the lab to speed up flowering, so the bees in your garden may be doing the same. If your flowers bloom earlier than you expected, check the leaves for tiny holes (they appear to have a half-moon shape); it could be a sign that the bees in your yard are nibbling them to get pollen sooner!
