Your Garden “Still Works” in the Winter

It’s hard for many gardeners to resist “cleaning up” their gardens in the fall or spring. But many moths and butterflies overwinter as caterpillars, pupae, and even adults in the soil surface, leaf litter, dead plants, twigs, and other hiding places in the garden. Other insects such as native bees, beetles, and more, need “messy” habitat to survive–year round.

The great spangled fritillary is just one example of a species of butterfly that depends on winter habitat. Its tiny caterpillars (larvae) hatch in early fall and nestle into plant litter to enter winter dormancy. In the spring, the caterpillars emerge and begin to eat and quickly grow. (Photo: courtesy of Dave Crawford)

Removing a garden’s protective layers means you may be unknowingly removing the very butterflies you are trying to attract (some pupae look exactly like leaf litter so you won’t even know you are removing them).

Even log piles provide the perfect spot for some moths and butterflies, as well as other insects, to lay eggs and hibernate.

Every yard should have a rotting log (or two!). Dead trees, rotting logs (also known as “snags”) are crucial habitat for a wide range of insects–the lifeblood of our ecosystem.

Many species of native bees lay their eggs in the cavities of stems or rotting wood: some excavate pith-filled stems while others make their home in pre-existing cavities in rotting wood. According to Heather Holm, in her excellent book Bees, An Identification and Native Plant Forage Guide, it is important to leave the garden alone in the fall and throughout winter. And because some native bees reuse these cavities in the spring, they should remain intact year round. Holm explains, “Then in the spring, cut off the top of the old stems about 15″ above the ground, leaving flower stalk stubble. No further maintenance is required. Within a few weeks new growth from the perennials hides the dry stems and within a year or two, the stems naturally breakdown.”

Stem stubble in the garden should be cut to around 15″ tall in late spring. Keep these stems intact 24/7. They will eventually break down and add nutrients to your garden soil.

The carpenter bee’s life cycle illustrates the need to keep natural nesting cavities standing year round. According to Heather Holm, “Small carpenter bees overwinter as adults and the following spring, may reuse the same stem that they hatched from for a new nest.” (from Bees, An Identification and Native Plant Forage Guide).

A small carpenter bee (Ceratina sp.) on Rosa blanda.  (Photo: courtesy of Heather Holm).
and excavating her nest in the end of a flower stalk stem. (Photo: courtesy of Heather Holm)
A pure green metallic sweat bee (Augochlora pura) nesting in a cavity in a decaying log. (Photo: courtesy of Heather Holm)

Lastly, as the life cycles of many insects take place underground at least part of the year, gardens and landscapes that use landscaping fabric (plastic or breathable) will eliminate a surprising amount of wildlife from the yard.

Keep your garden’s fallen leaves, plant stems, natural debris, and hiding places intact, not just in the fall, but throughout the year. Some insects require garden debris for more than just over-wintering habitat.  Your garden is one place where it’s OK to be messy! You will provide important habitat for bees and butterflies, and other beneficial insects (the lifeblood of our ecosystem) as well. A winter garden left intact will also provide winter seeds for birds, attract wildlife, and provide visual interest for you.

Thank you to Dave Crawford and Heather Holm for their contributions to this article.

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