Walk through any garden center and you will find narrow wooden boxes with vertical slots, sold as butterfly houses. They look inviting. Do butterflies use them? The honest answer is that evidence is thin, and the reports that exist suggest they are rarely used. This guide explains what is known, what is not and what to do instead.
The idea behind butterfly houses
A typical butterfly house is a tall, narrow box with slits in the front, intended to let butterflies enter and shelter from rain, wind and cold or to overwinter. Most butterflies, however, do not behave this way. Most species spend the winter as eggs, caterpillars or pupae, hidden in leaf litter, stems, bark or soil. A few spend winter as adults, tucked into tree crevices, wood piles or loose bark.
What the evidence says
Few studies have tested whether butterflies use manufactured shelter boxes. Many gardeners report that the boxes sit empty or are used by other creatures, such as wasps, spiders, earwigs, bees or even mice. That does not mean they never help, but it does mean they should not be your main strategy. If you buy one, treat it as an experiment and do not use it as a replacement for plants.
Butterflies that overwinter as adults
A handful of butterflies in the United States hibernate as adults, including the mourning cloak, eastern comma, question mark and Compton tortoiseshell in parts of the country. They tuck themselves in tree cavities, under loose bark and in woodpiles. These species are the ones most likely to use a shelter, and they are far more likely to find a woodpile or tree hollow than a store-bought box.
Monarchs in the Plains and Midwest do not overwinter locally. Eastern monarchs migrate to mountain forests in central Mexico. Western monarchs migrate to groves along the California coast. Our monarch guide covers their needs.
What really helps butterflies
- Host plants. Each butterfly lays eggs on specific plants where caterpillars feed. No host plants means no butterflies.
- Nectar plants. Adults need flowers from spring to frost.
- Sun and shelter. Butterflies bask to warm up. A sunny spot sheltered from the wind makes a difference.
- Puddling spots. Males gather on damp sand or mud to take up salts and minerals.
- Leaf litter and stems. Many species overwinter there as eggs, caterpillars or pupae.
- No insecticides. Even products marketed for garden use can kill caterpillars. Products that target caterpillars, such as Bt, harm butterfly larvae as well as pests.
Host plants for common butterflies
| Butterfly | Caterpillar host plants | Notes |
|---|---|---|
| Monarch | Milkweeds | The only plants monarch caterpillars eat |
| Black swallowtail | Dill, fennel, parsley, golden Alexanders | Plant extra herbs for them |
| Eastern tiger swallowtail | Wild cherry, tulip tree, ash | Needs trees |
| Painted lady | Thistles, mallows, hollyhock | Migratory; numbers vary yearly |
| American lady | Pussytoes, pearly everlasting | Prefers sunny spots |
| Red admiral | Nettles | Leave a patch of stinging nettle if you can |
| Great spangled fritillary | Violets | Larvae feed at night |
| Question mark | Elms, hackberry, nettles | Adults overwinter |
| Common buckeye | Plantain, snapdragon, false foxglove | Often seen on bare ground |
| Clouded sulphur | Clover, alfalfa and other legumes | Common in fields and lawns |
Nectar flowers worth planting
Use plants native to your region where possible. Good performers across much of the central and eastern United States include purple coneflower, blazing star, bee balm, butterfly milkweed, ironweed, asters, goldenrod, coreopsis and verbena. Sequence matters: choose some that bloom in spring, some in summer and some in fall, so that nectar is available at every stage of a butterfly's season.
Making a puddling station
Fill a shallow dish or tray with coarse sand, add water to keep it damp and set it in a sunny spot. A few flat stones to perch on help. Rinse and refresh it so it does not breed mosquitoes. Some people mix in a pinch of salt or place overripe fruit nearby, but plain damp sand and mud work for many species.
If you still want a butterfly house
- Mount it on a post or wall, 3 to 5 feet off the ground, in a sheltered spot facing the morning sun.
- Add bark or twigs inside, which can improve its use as a shelter.
- Check it once in a while, and clean it out in winter if wasp nests or debris fill it.
- Keep realistic expectations.
Frequently asked questions
Do butterflies use butterfly houses?
Rarely. Evidence is limited, and most reports describe them sitting empty or hosting other insects.
What is the best way to attract butterflies?
Plant native host plants and nectar flowers, provide sun and shelter, and avoid pesticides.
Which butterflies hibernate as adults?
Mourning cloaks, question marks, eastern commas and a few others. They use tree crevices, bark and woodpiles.
Should I clean up all my leaves in fall?
No. Leaf litter shelters butterfly eggs, caterpillars and pupae, as well as other beneficial insects.
Is Bt safe for butterflies?
No. Bt products designed to kill caterpillars can also kill butterfly and moth larvae.
