Fall clean up: leave habitat for birds and bees

By early fall many perennials in our Central Kansas gardens begin looking very tired and ragged and many gardeners begin to wonder if it is time to give plants a hard pruning to clean things up. Here are some considerations to take to mind before you begin cutting plants back in the garden.

Consider native insects and birds

Native insects, pollinators, and birds rely heavily on plants in local gardens (especially native plants) for food and protection to survive the winter. Plants that provide food, habitat, or both should be left standing when possible to aid their survival.

These coneflowers seed heads have been heavily fed on by birds during the winter season

Birds often seek out dense evergreen shrubs and trees or even ornamental grasses as shelter for overwintering, while native insects overwinter in different life stages. Some insects overwinter as adults, while others as egg, larva, or pupa. Many insects also overwinter in a state called diapause which is a state of dormancy where body activity slows dramatically to conserve energy and allow winter survival. These insects seek out various sheltered locations in gardens to overwinter. They enter hollow plant stems, burrow under leaf litter or under tree bark flaps or crawl into the protected crown area of many perennial plants. Some also nest in the ground itself or in cavities in the wood of trees or shrubs.

Most native bees are solitary and many (around 1/3) nest in plant stems. They will lay eggs in the stem and provision each egg with a nutritious ball of pollen and nectar. Bees will develop from eggs into larvae and adults that hibernate through winter. Most bees won’t emerge from these stems until the season after they begin nesting.

Photo: Josh Fuder, University of Georgia–example of mason bee nesting cells and similar to many other solitary stem nesting native bees

Examples of plants that provide either shelter or food for native insects and birds and should be left standing include: serviceberry, viburnum, elderberry, raspberry or blackberry canes, sumac, ornamental grasses, bee balm, coneflower, black-eyed Susan, coreopsis, goldenrod, liatris, sunflower, zinnia, aster, sedum, Joe Pye weed, rose, globe thistles and many more.

A method to use

For those interested in supporting pollinators but still like a tidy looking garden, there is a method you can use to help leave enough plant stems in your garden each season and still do *some* clean up.

For this example we’ll use coneflower. One way to minimize mess and still preserve pollinators is to cut the coneflower stems down to 15 to 18 inches tall in late fall (year 1). Ideally, the stems you leave will then be utilized by native bees the year after (year 2). Don’t remove the stems the following spring in year 2, rather leave them and let new coneflowers grow up around them.

Example: new growth from this aster will grow up through the previous year’s stems that are left for nesting habitat

During year 2 many native bees will utilize the year 1 coneflower stems to nest. The new generation of bees will then hatch from the year 1 stem by late spring or early summer of year 3.

By cutting plant stems back each year to 15-18 inches they can remain for the next two seasons to support the needs of pollinators.

Although this seems like a long time to keep plant stems, it is a good way to keep a maintained garden look while providing adequate stem nesting opportunities for our pollinators.

Leave some seed heads: Don’t forget that the seed head of many native flowers feed birds during the winter and so if possible it is best to still leave some seed heads in a portion of the garden.

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