Gardening for Butterflies

They are also extremely important ecologically. Butterflies pollinate flowering plants and serve as food for other organisms, thus forming an important link in the food chain. Populations have declined in recent decades, owing to increased pesticide use (especially herbicides); loss of fencerows; urbanization and other destruction of habitat; and loss of caterpillar host and nectar plants. Managing your garden for butterflies can help conserve butterfly populations as well as greatly enhance a traditional garden.

There are about 750 butterfly and skipper species in North America, and about ten times that number of moths. Butterflies, moths, and skippers combined form the order of insects named Lepidoptera, meaning "scaly winged." The wings are covered with thousands of tiny scales, which form the spots and stripes that we see. Skippers are considered an intermediate form between moths and butterflies. The body shape is similar to a moth's, but skippers are active during the day, like butterflies. One hundred forty-six species of butterflies and skippers have been reported in Pennsylvania. Of these, 24 have been documented only a few times and should be considered rare visitors.

Butterfly Life Cycle

The life of a butterfly is marked by four vastly different stages: egg, caterpillar, pupa, and adult. The egg hatches into a caterpillar, which immediately feeds on the leaf of the plant where it has hatched. In fact, rapid growth is the main objective of the caterpillar stage. You can see this reflected in the caterpillar's body structure--primarily a set of strong jaws for chewing and a digestive tract for processing food.

The caterpillar grows and molts, shedding its exoskeleton when that becomes too small. After four to six molts, the caterpillar pupates, or transforms. The new stage is termed the pupa, and the covering around the caterpillar is called a chrysalis (or cocoon, for moths). Protected inside the chrysalis, many of the caterpillar's body structures dissolve and reform into the distinctive butterfly shape.

Adult butterflies of most species emerge from the chrysalis 10 to 15 days later. They unfold and dry their wings, which must harden before they can fly. Adult butterflies feed on nectar, the sweet liquid in flowers. Adults mate during this stage, and the female deposits her eggs on an appropriate plant.

In temperate regions some butterfly species, such as mourning cloaks and many tortoiseshells, hibernate as adults during the winter. Others, like swallowtails, overwinter in the chrysalis. Some species overwinter as eggs and caterpillars. A few species, such as monarchs, migrate to warmer areas when it gets too cold for them; in Pennsylvania they are present only from late May to early November.

Butterflies are cold blooded and must depend on their environment for heat. To fly, their body temperature needs to be greater than 75°F. On cooler days they often bask with outstretched wings on a rock or other flat surface to store up heat energy. The dark patterns on many butterfly wings help the insects absorb solar energy. On cloudy, cool, or windy days, most butterflies remain in protected spots. You are likely to spot them in warm, sunny, calm areas where flowering plants can supply the butterflies with nectar.

Gardening for Butterflies

Because butterflies are attracted to flowers, it is easy to plant a garden that both you and they can enjoy. Some of the species you may attract are listed in the table at right. A butterfly-friendly garden contains both adult nectar plants and caterpillar host plants. A few common vegetables also serve as caterpillar host plants. Many butterfly gardeners plant extra vegetables, enough for them and their caterpillars. As an added bonus, butterfly gardens often attract hummingbirds.

A successful butterfly garden has several basic elements, listed below.

A sunny location

Since butterflies are cold blooded and need to be warm to fly and feed, you should plant your garden in a sunny area sheltered from the wind. Storms and windy days can batter a butterfly to bits. If there is no natural shelter, plant a windscreen such as spice bush or another flowering shrub that can provide both food and shelter.

Host and nectar plants

Choose the appropriate plants with a knowledge of butterflies common in your area, as well as their host and nectar plants. Caterpillars often restrict themselves to a single species of host plant or a single group of closely related plants. Caterpillar host plants of some common Pennsylvania butterflies are listed in the table below.

Adult butterflies are more flexible in their needs for nectar plants. Generally they prefer purple, red, yellow, orange, or pink blossoms; flat-topped or clustered flowers; and short flower tubes. A well-planned butterfly garden has blooming flowers throughout spring, summer, and early autumn. This provides a continuous food source and plants of varying heights to accommodate large and small butterflies. Examples of adult nectar plants are listed in the table at right. Butterflies are also attracted to weedy areas, so an area left unmowed and allowed to grow will further entice butterflies into your yard.

It is desirable to plant both caterpillar host plants and nectar plants in clusters. Butterflies are more attracted to groupings of flowers than to a single plant with a few blooms. Many cultivated flowers have been selected for their appearance, not for their fragrance or the amount of nectar they contain. Therefore, it is often better to choose common varieties for butterfly gardens instead of fancier hybrids. Common varieties may produce more nectar for the insects.

Minimal or no pesticide use

Limit your use of insecticides and herbicides, if you use them at all. Insecticides kill beneficial insects as well as those considered a nuisance. Herbicides are damaging to butterflies because they may eliminate sources of food for caterpillars and may poison them. For these reasons, areas managed for butterfly conservation should have minimal or no pesticide or herbicide application.

A particular pest species often is associated with a specific type of plant. By having a variety of plants, you reduce the potential for pest problems and, thus, the need for chemical controls.

Additional enhancements

Several other elements can be added to enhance a butterfly garden. Place a few rocks in sunny areas to give the butterflies a good basking surface. Also provide wet sand or mud. Males will often gather at wet sand patches and mud puddles. This phenomenon, called puddling, provides minerals and other nutrients that the males "gift" to females during mating. Experiment with wet sand patches to see if butterflies will use them.

Finally, many enthusiasts "sugar" their gardens to attract butterflies. They mash together a mixture of overripe fruit and stale beer. After letting the mixture warm in the sun a bit, they either paint it on tree trunks or soak sponges in it and tie the sponges to low-lying branches. The latter procedure has the advantage of not marking the trees, but it does obscure the attractive background of natural tree bark. Though the brew may sound less than delicious, it often is effective in drawing shier butterflies into the garden where the watcher can see them.

Enjoying Butterflies

With the publication of useful field guides, butterfly watching has grown more popular. All the hobby requires is an interest in butterflies, a notebook to record species, place, and time of sighting, and a basic knowledge of where to find butterflies. Low-magnification binoculars are optional, as most butterflies allow observers to get close enough for identification and careful observation.

Unlike bird watching, butterfly watching does not require getting up at dawn. Since the insects must be warm in order to fly, most do not emerge from their overnight shelter until mid-morning, around nine or ten o'clock.

For More Information

Books

• Lewis, A., ed. Butterfly Gardens: Luring Nature's Loveliest Pollinators to Your Yard. New York: Brooklyn Botanic Garden, 2007. (Features an extensive list of host and nectar plants along with color photos.)
• Glassberg, J. Butterflies Through Binoculars: The East. Oxford University Press, 1999. (An excellent field guide for identifying butterflies. Also includes information on butterfly photography.)
• Opler, P. A., and Malihai, V. Eastern Butterflies (Peterson Field Guides). New York: Houghton Mifflin Co., 1998. (Field guide featuring descriptions of 524 butterflies. Includes pictures, drawings, and range maps.)
• Xerces Society. Gardening for Butterflies. Timber Press, 2016. (Describes ways to attract butterflies and other beneficial insects to your garden. Includes a list of plant species that attract butterflies; butterfly food plants, seeds, and plant sources; and a bibliography.)

Websites

• The Butterfly Website includes tips for gardening as well as many links to other butterfly sites.
• The National Wildlife Federation has many informative pages about butterflies.
• Monarch Watch is maintained by the University of Kansas Department of Entomology and the University of Minnesota Department of Ecology. The site contains a wealth of information about monarchs. Included are curricula for elementary and middle school classes as well as research and conservation projects suitable for classes or individuals.
• North American Butterfly Association is a membership-based organization dedicated to increasing public enjoyment and conservation of butterflies. Members receive the newsletter Butterfly Gardener.

Authors

Prepared by Judith Mank, former graduate research assistant, and Margaret C. Brittingham, professor of wildlife resources

Acknowledgement

Partial funding for this fact sheet was provided by Pennsylvania's Wild Resource Conservation fund.