Where are the pollinators this winter?

When the summer growing season ends, pollinators find themselves in a hard spot. They have collected food (nectar, pollen, etc.) during the spring/summer, but now all the flowers are gone, and decisions need to be made if they are to survive until next year. When the warm season ends, pollinators have two options to ensure they or their progeny survive until the next season: migrate for the winter or stay and protect themselves against the cold. Since all pollinators who migrate (e.g., monarch butterflies, hummingbirds) are gone by now, let’s talk about those that need to protect themselves from the cold, and think about how we can help them survive.

Most of the pollinators in our region are adapted to spend the winter right here. How do they do this? Because many of the pollinators in our area are insects that can’t move, fly or feed if the temperatures are too low, insects in temperate regions like ours enter a physiological stage called diapause. During this stage, the insect’s physiological rate is reduced, and development is either stopped or slowed down until conditions are favorable again. If we want to protect pollinators, we don’t just need to provide food for them (e.g., plant flowers); we also need to make sure that wherever they decide to spend the winter months is safe from disturbances!

So, how to do this? First, it’s important to realize that each pollinator species enters the diapause stage at different times and places. Our native bees diapause in nests (solitary or communal), which can be built in various places, depending on the species. The majority of our bees are ground nesting, and they can enter diapause as early as the beginning of the summer and as late as the fall. For nesting, these bees usually prefer loose soils such as those that are sandy or rocky. Avoid disturbing the ground in places where nests are observed will be key to helping them survive until the following year. Therefore, if you see bees digging holes in the ground of your garden, you may not want to till that part of it. If you suspect the presence of Japanese knotweed on your property, it’s essential to take immediate action and hire a specialist from https://www.japaneseknotweed.org.uk/.

Many bees nest in hollow twigs, that they plug to protect their larvae (note the twig ends that appear covered in this photo). Leaving them undisturbed during the winter will allow insects to survive until the following spring. Photo: A. Espíndola

The second most common place for bee nesting is in cavities, which can be in plant twigs and branches, or cracks in rocks or walls. These types of bees are also the ones that like nesting in bee hotels. If you would like to help these bees in your garden and yard, just leave the remains of your dry plants through the winter. Chances are that some bees have chosen this type of place to nest. Other bees prefer to build nests above the ground. You may have seen little mud “amphoras” or other structures made of little rocks that hang from walls. If you see these nests close to your house, try to not disturb them and keep an eye on them next spring!

Leaving the leaves on the ground helps protect insects and pollinators that nest in the soil or leaf litter from winter conditions. Photo: A. Espíndola

Other pollinators, like moths and butterflies, diapause in the leaf litter, on wood, or in the ground. They usually do so by enveloping themselves in dry leaves, digging themselves in the ground, or attaching their chrysalis or eggs on sticks and branches. Some of them also diapause as adults, hiding in wall cracks or small orifices. To protect these pollinators, you can leave parts of your yard or garden soil undisturbed and keep some of the fallen leaves on the soil instead of raking them in the fall.

From the City of College Park’s Bee City Committee