I am a butterfly enthusiast who does a lot of talking and writing on the
subject of gardening for butterflies. Aware of my intense interest in
butterflies, many people have said to me, "You know, Rose, there just
aren't as many butterflies around here as there were 20 or 30 years
Unfortunately, these people are correct in their observations. For many butterfly species, their population has declined by approximately 40% in the last 40 years.
What's happening to the butterflies? Entomologists claim that the use of pesticides and the destruction of natural habitat are probably the leading causes of declining butterfly populations. This means that humans are responsible for the dwindling numbers of butterflies. But humans can save the butterfly population too. With just a little effort, we can create a haven that is favorable to butterfly survival and reproduction.
Many people are gaining an interest in gardening for butterflies, most of them incorporating nectar producing annuals, perennials, and butterfly bushes into their gardens. And that is great---but we should go one step further when planning a butterfly garden. To significantly increase the butterfly populations, we have to provide food for the baby butterflies, caterpillars.
For each species of butterfly, its larva (caterpillar) can only digest a specific type of plant foliage. Some caterpillars are able to thrive on a number of closely related plants while others are able to digest just one specific plant species. This specific plant material is referred to as the 'larval host plant', the 'caterpillar host plant', or the 'butterfly host plant'. Isolate a caterpillar with an unsuitable host plant and it will starve; or it will eat, sicken, and die. One larva's staple is another one's poison.
What makes a butterfly species abundant in one area and unseen in another often has something to do with the availability of caterpillar host plants. In order for a butterfly species to survive in any location, ample food must be available for its caterpillars. Without caterpillars, there couldn't be butterflies.
Most butterflies live for just a few weeks or a few months. For the species to survive, therefore, the females in that species must lay fertile eggs before their short lives end. And to ensure the survival of the caterpillars that will emerge from the eggs, eggs must be laid on or near the appropriate larval host plant. When the eggs hatch, the tiny caterpillars usually eat their egg casings and then begin to feed on the host plant. After reaching their full size (often just a few weeks after hatching from the egg), the caterpillars stop eating and typically crawl away from the host plant. Each finds a sheltered location to pupate. The caterpillar sheds its skin, transforming into a chrysalis (pupa). Later a butterfly emerges from the chrysalis. (You can learn about the life cycle of a butterfly by clicking on 'Monarch Metamorphosis' on our 'Milkweed' page.)
For every butterfly species that is native to Pennsylvania, there is a native plant that hosts its caterpillars. Milkweed is the host plant for the monarch butterfly's larvae, thistle is one of the host plants for the caterpillars of the American Lady butterfly, stinging nettle hosts the Red Admiral's caterpillars, wild carrot is a host for the larvae of the Black Swallowtail butterfly, and plantain is a host for the caterpillars of the Baltimore Checkerspot and Buckeye butterflies.
While it would likely increase the number of butterflies in the vicinity of one's property, most people would be reluctant to incorporate milkweed, thistle, stinging nettle, wild carrot, and plantain into their landscaped gardens. These plant species are classified as ugly, invasive weeds.
Fortunately, the caterpillars of many butterflies can utilize beautiful cultivated plants as hosts. Along with plantain, turtlehead (Chelone) serves as a host plant for the Baltimore Checkerspot caterpillars. Turtlehead is an attractive perennial plant that usually grows to about 30" high and produces lovely white or pink flower spikes. It prefers moist soil and full sun to partial shade.
Aside from wild carrot, Black Swallowtail caterpillars are able to digest dill, parsley, fennel, rue, and even cultivated garden carrot foliage. Rue serves as a host for not only the Balck Swallowtail but also the Giant Swallowtail. American Lady caterpillars (and also Painted Lady caterpillars) utilize 'Silver Brocade' Artemisia (Artemisia stellariana 'Silver Brocade') as a host plant. And Painted Lady butterflies often lay their eggs on hollyhock, balsam, or borage.
To host the caterpillars of the famous monarch butterfly, there are several milkweed (Asclepias) species which are elegant enough to be planted in even the most formal of gardens. White-flowering swamp milkweed (Asclepias incarnata 'Ice Ballet') is available at many nurseries, grows 30"-36" high, is very hardy, and is highly utilized as a host plant for monarch caterpillars. Tropical milkweed (Asclepias curassavica) is native to South America and must be grown in the United States as an annual. Producing clusters of bright orange and yellow flowers, tropical milkweed grows 30"-36" high, and is also highly utilized as a Monarch host plant. Hairy Balls Milkweed (Asclepias physocarpus) is another tropical which must be grown as an annual in the U.S. Also known as Swan Plant and Balloon Plant, Hairy Balls Milkweed grows 48"-60" high and produces clusters of delicate lavender/cream bicolor flowers. It too, is highly utilized as a Monarch host plant.
The native host plant for the caterpillars of the Meadow Fritillary and the Great-Spangled Fritillary butterflies is the sweet violet, but pansies (actually cultivated violets) sometimes serve the purpose. Native Asters host the caterpillars of the Pearl Crescent butterfly, but many hybrid New England Asters are acceptable. Native legumes are the hosts for the larvae of the Silvery Blue butterfly but Lupine serves the purpose well. Lupine is a well known perennial that produces lovely flower spikes in May and June. You will find lots of other host plants listed on our 'Butterfly Host Plant' page, where you will also see pictures of some of the butterflies I have referred to in this article.
Of vital importance to butterfly conservation is human willingness to refrain from the use of chemical insecticides in or near the butterfly garden. We must remember that butterflies are, after all, insects. Insecticides, therefore, have no place in a haven designed for butterflies.
By getting involved in butterfly conservation we will be rewarded with an abundance of colorful butterflies in the years to come. If we forget that butterfly populations are dwindling and do nothing to help them in their struggle to survive, we may one day pay the price. Our beautiful butterflies may disappear.
|Baltimore Checkerspot||Turtlehead (Chelone)|
|Black Swallowtail||Dill, Parsley, Fennel, Rue, Queen Anne's Lace|
|Tiger Swallowtail||Wild Cherry, Yellow Poplar|
|Spicebush Swallowtail||Spicebush, Sassafras|
|Giant Swallowtail||Citrus trees, Prickly Ash|
|Great-Spangled Fritillary||Sweet Violets|
|Meadow Fritillary||Sweet Violets|
|Question Mark||Nettle, False Nettle, Elm, Hops, Hackberry|
|Comma (Hop Merchant)||Nettle, False Nettle, Elm, Hops|
|Mourning Cloak||Willow, Birch, Elm, Hackberry|
|Painted Lady||Hollyhock, Pearly Everlasting, Thistle|
|American Lady||Artemisia 'Silver Brocade'|
|Common Buckeye||Snapdragon, Heliotrope, Verbena|
|Viceroy||Willow, Aspen, Poplar, Cherry|
|Red-Spotted Purple||Wild Cherry, Poplar, Aspen|
|Dainty Sulphur||Sneezeweed (Helenium)|
|Gray Hairstreak||Hibiscus, Hollyhock, Rose of Sharon|
|Hummingbird Clearwing Moth||Viburnum, Honeysuckle|
Back to the Butterfly Host Plant page.
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Copyright © 2001 [Rose Franklin's Perennials]. All rights reserved.
Revised: January 18, 2015