November 28, 2021

McKenzielee Blog

Wicked Clever House Experts

Hold off cleaning up the garden and help beneficial insects

3 min read

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For insects such as this bumble bee, pollinator boxes or hotels aren’t as beneficial as a natural habitat.

Johnson County Extension

A decade or so ago, it was an easy decision on how to handle the garden at the end of the season. Previous recommendations were to remove frost-killed plant debris, eliminating potential insects and diseases before the next growing season.

With additional research, we now know it is better to wait. Not only were we removing harmful insects, but also the beneficial ones, which are the base for the web of life.

Beneficial insects come in all sizes and shapes. Butterflies, moths, bees, wasps, flies and beetles each have a slightly different life cycle and means of survival. Once spring arrives again, these insects emerge ready to pollinate our crops or feast on damaging pests.

Cleaning up the garden in the fall can remove their overwintering stages as they spend winter as eggs, larvae or even adults. Insects have developed sophisticated ways to protect themselves from harsh winters. Some burrow into the soil, snuggle into leaf litter on the ground, or drill into hollow stems of plants.

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A leaf cutter bee making a nest. Johnson County Extension

The former recommendation was to tidy up in the fall, leaving a well-manicured garden. Swooping in after a frost, the garden tasks included cutting back perennials and raking every leaf from the garden. Now we have learned these spaces are necessary to sustain life from one season to the next.

By removing every last stem and leaf, we take away the natural habitat for these beneficial insects. While we may not like the messy look over the winter, the pollinators prefer a little more unkempt manner.

Some butterflies, moths, beetles, bees and flies like to work their way into nooks and crannies of tree bark, leaf litter and other protected places to spend the winter. Once they are sheltered, butterflies such as the mourning cloak, comma and question mark develop an anti-freezing substance that stops the blood from freezing and keeps them alive until spring.

Hawkmoths burrow into the soil and form cocoons protected from the extremes of winter. Others, such as Cecropia moths, spin silken cocoons and hibernate in leaf litter on the ground or in rolled up leaves.

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A cocoon of a Cecropia moth. Johnson County Extension

Beneficial solitary mason bees prefer to work their way into dead hollow stems of perennials and grasses. The larvae stage pupates in late summer, and the young adults spend the winter in a state known as diapause. In this suspended state of survival, they wait for spring to arrive.

The use of pollinator bee boxes or hotels mimics these natural nesting cavities. Current research questions whether these bee boxes do more harm or good.

The concern is many of the insects using them are solitary. They don’t live together in colonies. Bee boxes force them to overwinter in proximity, which is not natural. There are also concerns that manufactured boxes harbor disease, reducing the chance of survival.

If we genuinely want to do all we can to protect beneficial insects, we must be tolerant and embrace a naturistic garden. Allow leaves, stems, and even woody debris to remain in the garden.

Then, once spring arrives, wait to clean up until consistently warm temperatures into the 50s arrive. These temperatures signal the insects have emerged, ready to get to work for another season of pollinating our plants.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Have a question for him or other university extension experts? Email them to [email protected]

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