Don't Dead Head Your Fall Perennials!

By Joanne K., Pitt County Extension Master Gardener Volunteer

Come fall the perennial garden starts to look pretty tired with brown stalks and seed heads. The urge to cut everything to the ground for a neater looking flower bed is strong.

However, don't do it! Those stalks and seed heads are critical sources in protecting the life cycle of pollinators.

Many native perennials, such as this purple Coneflower, offer both food and nesting resources for pollinators.
Image by Charlotte Glen, NC State.

During the spring and summer, native plants in particular serve as host plants and/or food sources for beneficial insects, birds, butterflies, and moths. As such, they need protection from pesticides.

However, these host plants continue to be important when fall arrives and flowering is over. Knowing when to cut back the stems and seed heads is critical to the success of the pollinator life cycle.

Pollinators include many species of bees and insects like moths, butterflies, wasps, beetles, and flies. More than a dozen species of bees and beneficial solitary wasps build

their nests and lay their eggs in hollow stems. Different species have different life cycles with different needs at different times.

Plants that support pollinators include Black-eyed Susan (Rudbeckia), Coreopsis (Coreopsis), Joe Pye Weed (Eutrochium species), Purple Coneflower (Echinacea purpurea), and Sunflower (Heliopsis). The seed heads of these plants provide nourishment for birds in winter along with giving structure and visual interest to the winter garden.

A recent NC State study* on when and how to cut back perennial stems recommends the following:

• Trim perennial stems back in fall or winter to leave 1-2 feet standing above ground. While these stems will not be occupied the first winter, they will be available for pollinators and beneficial insects to use as nesting sites the following spring and summer.
  
• Waiting until late winter to trim stems will give birds and wildlife time to feed on seed heads, increasing the number of species supported.
  

Trim perennial stems such as these Black-eyed Susans by leaving 1-2 feet standing above ground level to provide habitat for stem-nesting pollinators.
Photo from NC State Extension.

• Once trimmed, the stems require no further maintenance and will naturally disintegrate in future seasons.
  

A black swallowtail chrysalis is attached to this Coneflower stem. Photo by Debbie Roos.

Ceratina bees are one of the pollinators found nesting in old stems.
Image by Elsa Youngsteadt, NC State.

Seed heads of Ironweed and Bee Balm against a backdrop of Pink Muhly Grass in the late fall provide food for birds.
Photo by Debbie Roos.

Of course, any perennials with pest or disease problems should be removed.

Other important ways to support pollinators include:

Using leaf litter as mulch in your garden and at the base of trees provides a home for bees and butterflies. Bumblebee queens hibernate just below the soil surface using decayed leaves for protection from winter elements.

This pearl crescent butterfly (Phyciodes tharos) is feeding on the dried head of a Black-eyed Susan.
Photo by Joanne K.

Many butterflies use the leaf litter to overwinter as adults, eggs, caterpillars, or chrysalids. The luna moth (Actias luna) hides its cocoons and chrysalids in the dried leaves until spring when they come out as adults.

Don't forget to leave some bare ground. Solitary bees build their nests in the ground. Leaf litter can prevent them from nesting.

In a corner of your garden, build a brush pile of twigs and bark. Some butterflies and many beneficial insects such as fireflies (Lampyridae) will hibernate there. The piles also provide hiding places for small songbirds.

Create a rock pile that provides a home for a variety of beneficial insects, including leaf cutter bees, bumble bees, and ground beetles.

Pollinators are essential for the success of our food crops and ornamentals. By following some or all of these practices in your garden, you can help to ensure the survival of our pollinators, who, in turn, ensure the future of our food supply and our flowers and trees.

A layer of leaves in the pollinator garden provides protection for overwintering pollinators.
Photo by Debbie Roos.

For more information on protecting pollinators, check these websites:

* Growing Knowledge to Protect Pollinators at
https://emgv.ces.ncsu.edu/2023-annual-report/growing-knowledge-to-protect-pollinators/

Fall Chores in the Pollinator Garden: Leave the Leaves and Save the Stems! at
https://growingsmallfarms.ces.ncsu.edu/2022/12/fall-chores-in-the-pollinator-garden-leave-the-leaves-and-save-the-stems/

Pollinator-Friendly Native Plant Lists at
https://xerces.org/pollinator-conservation/pollinator-friendly-plant-lists