Keeping Pollinators in Mind This Fall and Winter
I was outside a few days ago and started to see indications of the pending change of seasons. On several trees, leaves had started to shift color and a few floated to the ground as a breeze kicked up. A flock of geese flew overhead in their power “V” formation which made me start thinking about football. I also noticed several late-season plants in flower such as rabbit brush and asters that I know to push the limit for when the first real cold snap hits.
I panicked as I realized we would soon be entering fall with winter not far behind. How had I not accomplished all my summer adventures and summer chores? I was not ready to transition to preparing my home and landscape for winter. Just like the trees, geese, and flowers, many other tiny creatures around us are also cueing into the signs of change, shorter days, cooler temperatures, and their own lifecycle rhythms that will start preparing them for the less hospitable conditions that lie ahead.
Many insects that live in our yards, parks, and natural landscapes are well adapted and have varied strategies to persist through the cold winter and shoulder seasons since they require the sun’s warmth to be able to move and function. Where do the insects go and what happens to them during these colder months? Most seek sheltered locations, and we can help them by providing opportunities to find shelter as we go about fall yard chores. Most importantly, we can leave dead flower stalks in place and leaves on the ground. Before discussing these actions more in-depth, a little background first on the common life-forms of insects and how these forms help pollinators and other insects survive and cope with the long months of wind, chill, and snow.
Some insects take advantage of the egg stage, persisting through winter as a small, well-protected capsule, resilient to changing external conditions and requiring only minimal gas exchange with the outside world. Examples of insects that overwinter as eggs include the Melissa blue butterfly, a small blue butterfly with a red border of dots on its wings, praying mantids, and crickets.
Woolly Bear Caterpillar. Photo credit @ Christian Holland.
Other insects use the larval stage to overwinter. To make it through, the larvae halt or slow growth and go into a type of hibernation or diapause to wait out the winter and become active again once spring’s warm sun returns, plants begin to grow, and flowers bloom. The caterpillar of the viceroy butterfly (a monarch mimic) and the woolly bear caterpillar are examples. Many native bees also overwinter as larvae within their nests in protective holes in the ground or in wood to wait out the cold.
Butterflies and moths overwinter during the pupa stage, as the hardened outer pupal casing, more commonly called a chrysalis (butterflies) or cocoon (moths), helps protect the transforming insect within and provides a greater buttress from cold. Swallowtail butterflies, gray hairstreaks, and the silver-spotted skippers rely on this state to escape the cold.
Finally, some insects survive winter in the adult stage with the ability to be mobile and fly or move around as soon as conditions warm up enough enabling them to take advantage of early spring flowers and get a jump on starting the next generation. Butterflies such as the morning cloak and Milbert’s tortoise shell can be seen early in the spring as they escape from their well-protected shelter in a tree crevice, wood pile, or similar sheltered location. Queen bumble bees and some species of sweat bees overwinter as adults seeking holes in the ground to wait out the cold.
The key to survival in any of these stages is finding a suitably sheltered location to await spring as none of the forms are able to move in the chilly months. With this background in mind, let’s revisit the two important actions homeowners and gardeners can undertake to help provide winter shelter and habitat for pollinators and other insects: save the stems and leave the leaves.
Save the Stems
Leafcutter bees collage. Photo credit @ Sarah Morris, Xerces Society.
We often cut back and remove dried flowers and stems from our gardens in the fall to tidy up and prepare space for the following year’s flowers. However, leaving flower stalks with pithy centers such as sunflowers, golden rod, echinacea, beebalm (monarda), and raspberries through the winter provides a vital winter shelter for bees and other insects. Tunnel-nesting solitary bees such as small carpenter bees and leaf-cutter bees will create egg chambers within these hollowed out stems where the next generation of bees will grow and mature. The maturing bees will remain in their chambers overwinter, emerging the following spring to repeat the cycle of visiting flowers, finding mates, securing stems, and producing another generation that will again overwinter. While holding off on your fall pruning of flower stalks, leave the dried flowers as the seeds to provide beneficial food for an overwintering bird or other wildlife. Then in early to mid spring, cut off the flower heads leaving intact stalks at various heights from 8-24 inches for bees to find and use. These stalks will be the overwinter shelter that will house the following year’s brood of bees.
Leave the Leaves
Photo credit: Xerces Society, Suzanne Granahan.
Another fall clean up ritual is promptly raking up and removing the leaves that start amassing on the ground in our yards and gardens. However, many small critters and pollinators are dependent on fallen leaves for cover, shelter, and insulation from the elements. The western tiger swallowtail butterfly will overwinter in a chrysalis hidden on tree trunks or on the ground among the leaves as will the caterpillar of the hackberry emperor butterfly being rolled up in them. Leaves also provide shelter for spiders, beetles, lacewings, millipedes, mites, snails and many more of our yard’s tiny and useful residents. To help provide needed leaf resources and shelter, consider leaving some areas of your garden or yard with the leaves not cleaned up. If you are concerned about leaving thick piles or layers of leaves smothering the plants or grass below, remove some of the leaves to leave a thinner layer. The leaves can then either continue to stay in place into spring and become beneficial mulch or can be raked up and put in the compost. Raking or blowing the leaves provides better protection for invertebrates and pollinators than shredding the leaves with a mower or leaf shredder. If we resist the urge to pick up all the leaves, the invertebrates that benefit from that winter cover will make our gardens and yards livelier in spring and summer.
Pollinators are crucial to the future success of our gardens and natural spaces. Once you’ve become comfortable with leaving a little mess, then pass along what you’re doing and why to a neighbor. It may help them be less worried about what you’re not doing, and may even help them create better pollinator habitat too.
Photo credit @ Matthew Shepherd, Xerces Society.
The following sources were used to inform this blog and are helpful if you’re seeking more information:
The Xerces Society has helpful guidance and information about Nesting & Overwintering Habitat for pollinators and other beneficial insects
More about the importance of leaves as winter habitat from Xerces is available at:
