I understand the desire to clean up your garden after flowers fade and die. Shriveled brown leaves, blossoms and stems are not as appealing as the bright flowers that dominate summer and fall. However, they are beneficial to overwintering pollinators.
Plenty of beneficial pollinators overwinter in gardens, using plants and debris that are left behind to survive. If you have a pollinator garden or have a garden filled with native flowering species that help pollinators during the summer and fall, leave them standing to provide cover through the winter.
Which pollinators overwinter in garden debris?
Butterflies and moths. Various species of butterflies and moths can survive winter by hiding under garden debris, others are active during the winter months, some overwinter as a chrysalis and a few can survive as caterpillars.
These species hibernate under bark and dried leaves:
- Mourning cloak butterflies
- Comma butterflies
- Question mark butterflies
These species remain active:
- Winter moths are active between November and February.
- December moths are active in November and December.
These species overwinter as a chrysalis:
- Cabbage white butterflies
- Sulphurs butterflies
- Members of the swallowtail family
- Hawk moths spend the winter in warm cocoons underground.
- Cercropia moths hibernate in chrysalis form.
These species survive as caterpillars:
- Red-spotted purple butterflies
- Meadow fritillary butterflies
- Viceroy butterflies hibernate among the vegetation, in seed pods, in silken nests and in rolled-up leaves.
Bees. Although they are often overlooked because they don’t have colonies, solitary bees actually pollinate more efficiently than honeybees. During the winter, many of them hide in the hollow stems of bee balm or ornamental grasses. Others burrow into the ground to overwinter or make use of man-made bee hotels.
- Red mason bees spend the winter as young adults in an unanimated state inside their nest. They build nests in dry hollow stems, in holes in wood and in bee hotels.
- Leaf cutter bees. These bees are another cavity nester. They overwinter bee larvae in nesting holes until next summer.
- Wool carder bees. These bees are also cavity nesters. They overwinter in hollow reeds and stems with holes around 3/8-inch in diameter. they will also use nesting blocks, with the correct size holes and bee hotels.
Hoverflies. Hoverflies overwinter in two ways. Some hide in soil as full-grown larvae and others find shelter as adults. The overwintering adults appear on the first warm days of spring, searching for aphid-infested plants to lay their eggs on, as the larvae of most species feed on aphids.
Ladybugs. There are more than 400 ladybug beetles species in North America that feed on common garden pests — aphids, mites, white flies and scale insects. One ladybug can eat a dozen insects a day, so gardeners and farmers love them. Although invasive species, such as Asian lady beetles, often find their way into homes and become pests, native species only overwinter outside. They rely on cover under rocks, in hollow logs and beneath leaves to survive until spring.
Others. Wasps, ants and midges — a small two-winged fly — are other beneficial pollinators that overwinter.
Clean up your garden in the spring
Wait until April to rid your flower beds of wilted plants and debris. The pollinators that live there will thank you by ridding your garden of pests and ensuring beautiful blooms in the spring.
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Do you happen to know what percentage of the moth’s in Ohio are moths who overwinter in leaf debris?
I do not know the exact percentage of moths that overwinter in leaf debris. But I do know that many moth species overwinter as caterpillars in leaf debris. When you see woolly bears in the fall, crossing your yard, the street or a sidewalk a habitat of old leaf debris is what they’re looking for to hunker down for the winter.