Scientists recently discovered that these pollinators can actually make plants speed up flowering so that nectar becomes available sooner.

By Andrea Beck
May 28, 2020
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Have you ever noticed some of your flowers appearing a little bit earlier than you expected them to? There are a few different reasons why your garden might start blossoming early, including climate change (warmer weather speeds up plant growth in general), or even planting bulbs a little too shallowly. However, scientists recently discovered a new cause for flowers blooming earlier than usual: Hungry bees. 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 to cause the flowers to bloom up to 30 days ahead of schedule.

Credit: Albe84/Getty Images

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 a drought or plant disease), they’ll flower faster, which 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 going on, 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 leaves themselves, the plants flowered quicker but not as quickly as the ones the bees had nipped. This raises the possibility that there's something in the bees’ saliva that helps speed up flowering even more than just damaging the plant.

The scientists also saw two wild bee species chewing holes in leaves outside the lab to speed up flowering, so it’s possible that the bees in your garden are doing the same thing. If your flowers are blooming earlier than you expected them to, 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!

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