Butterflies are delightful flying people enticed to our earth-bound gardens by suitable and safe habitat. We invite their presence with leafy host plants and nectar-producing flowers, and protect butterflies by planting proper host plant species and avoiding use of harmful pesticides. Gardeners also help conservation efforts to support and restore endangered butterfly species by cultivating host and nectar plants in private gardens along migration corridors and in summer ranges. These add to large-scale efforts to preserve suitable habitat and associated plants threatened by development and invasive weeds that have poor host and nectar values compared to native plants. Some conservation projects include all of North America, as with monarchs, while others are extremely site-specific, such as the San Bruno elfin found only in a few tiny populations south of San Francisco (and primarily on San Bruno Mountain in San Mateo County).
Although there are general requirements for butterfly gardens, specific details can vary dramatically depending on your location. I’m focusing on butterfly life history details that affect garden design, plus offering a broad view of the subject that will help you determine what is best for your area. I’ve lavishly added links to resources of specific butterflies, host and nectar plants, and other habitat features that will fine-tune your planning.
Bees sip honey from flowers and hum their thanks when they leave.
The gaudy butterfly is sure that the flowers owe thanks to him.
Rabindranath Tagore
WELCOME TO THE SATURDAY MORNING GARDEN BLOG
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Growing seasons, locally native butterflies and associated host plants, endangered species, adjacent habitat (such as urban and agricultural) all influence what is most suitable for your garden at your home in your locale. What is a lovely suitable flower for my area may be an invasive nightmare for yours. Plants that easily handle my mild winters and long growing season might never flower long enough to be worth the trouble in colder areas. No garden is an island unconnected to the larger world, so planning for butterflies also involves seeing your garden as part of the regional landscape. I’m not going to admonish against pesticide use as I figure everyone knows this. But I will note it isn’t solely direct effects of pesticides on larval and adult butterflies that are damaging. Harming other pollinators and affecting vegetation composition through insecticide and herbicide use have serious consequences to butterfly habitats and plants.
BUTTERFLY BASICS
Life Cycle
Let’s begin with the butterflies themselves. How long do larvae need the host plants before transforming into adults? How long do adult butterflies live? Where do the butterflies sleep and where are they during winter? These questions have different answers depending on species, region, and time of year. The general life cycle of butterflies from egg to adult is illustrated in this article from The Butterfly Site. Usually larvae to pupate times are 6-8 weeks, and adults live only a week or two. So your garden’s flowers are enticing someone whose flighted presence is seen for only two weeks, while the host plants must feed the caterpillars for at least a month.
Larval form and their host plants
As a gardener, if you wish to support the adult butterfly you need to be sure that proper host plants are available. Host plants aren’t required in your garden, but their presence increases your butterfly potential. They must be in adjacent habitat areas, at least. Some species lay only on one plant species (e.g., monarchs and Indian pipe swallowtails), others may have a variety of hosts, such as other various swallowtails that use different plants in the Carrot Family (Umbelliferae). To learn what butterflies occur in your area, you can begin with the searchable databases from Butterflies and Moths of North America and The Butterfly Site. Myriad websites narrow down the state lists of butterflies for particular regions by county or geographic area, such as this page of results I obtained by using the search terms: California butterflies.
You’ll note that nurseries offer information on regional butterfly species, and these nurseries also are a good source of host plants, although double-triple-check information as they may not be accurate (and in some cases might be harmful). If you are especially interested in supporting endangered butterfly species, begin with this list of federally threatened or endangered butterflies in the United States. Some states also list butterflies that are state endangered, but not all states include invertebrates in their listing program. These are the inverts, including butterflies, listed by California.
Be sure to offer enough host plant vegetation to support the larvae during the one to two months they eat the plant - and don’t expect the host plant to add beauty to your garden except for the butterflies it nurtures. Larvae are tiny when they hatch and eat constantly, so they can demolish host vegetation as they grow to fat sassy easily seen caterpillars ready to pupate. Host plants for larvae are region-specific depending on the butterfly species in your area. To learn which host plants these butterflies require search “butterfly host plants in (state/county)” for your area. Here’s an example of one website with great photos for the Eugene/Salem Oregon region.
How butterflies choose where to lay eggs
Each kind of butterfly will only lay eggs on the correct plants. Sometimes they have a range of plants on which they lay their eggs but some species will only use a single kind of plant and then only where it is growing in the right place. This may be where there is plenty of sun for the caterpillars to get warm ( The Small Tortoiseshell does this) or it may be where there is less likelihood of the caterpillars being eaten ( The purple Emperor does this.)
The female butterfly will taste the plant with her feet and carefully choose the correct place to lay her eggs. This is determined by the presences of certain important taste chemicals in the plants. The choice of foodplant is very important. Scientists who studied a checkerspot butterfly . . . once found that the butterflies could tell plants from the site from which they came from apart from the same plants growing elsewhere. Even though the butterflies also occurred in the other place.
The El Segundo Blue choses only one kind of plant and the caterpillars are poisoned by the foodplant used by the butterflies just a mile or two away. The butterflies are said to be just a race of the same species and there is only a small difference in the markings that is visible to people.
Adult Butterflies and their plant choices
The colorful adult butterflies choose flowers based on color. They see the ultraviolet portion of the spectrum, which humans don’t, and flowers signal their presence using ultraviolet as well as colors we see. A range of colors attract butterflies, but in general white, pink, purple, red, yellow and orange are most attractive, and blue to green flowers are least favorite (this varies by butterfly species so general doesn’t mean always). Many flowers have ultraviolet patches on the petals that attract butterflies and other insects such as bees.
A wide variety of flowers that bloom throughout the growing season is important to keep butterflies in your garden and support successive generations throughout the season. You can ensure this by planting flowers with different bloom periods, and by staggered repeat plantings of those that bloom all season. Planting flowers in clusters of same species or color of blooms helps attract the near-sighted butterflies from a distance. Butterflies roam around looking for suitable plants, they don’t have any established pathways, nor do they communicate plant locations as do honey bees.
The types of flowers and inflorescences affect butterfly choices. They tend to feed more on small flowers held in umbels (umbrella shape, see dill inflorescence photo below right) or flowers with large petals (coneflower for example, shown below left). Of academic but not practical interest, flowers with short nectar tubes and strong fragrances are favored, and the ideal nectar is high in amino acids and about 20 percent sugar. Generally, the flowering plants that attract butterflies also attract hummingbirds.
A nectary is a flower structure that secretes nectar and is located near the base of the ovary or near the base where sepals and petals attach. This illustration shows the parts of a flower including nectaries.
What else is needed in addition to host and nectar plants
Depending on your climate, a butterfly garden generally is best in an area that receives at least six hours of direct sunlight. Because butterflies can't regulate their body temperature very well they need a place to bask in the sun and someplace to go for protection from wind and rain. But they also need water, which is best provided in a shallow dish filled with pebbles or marbles. They only sip liquids for nourishment, but not just from flowers and water dishes. They enjoy juice from rotten fruit, and may even drink sweat and liquid animal waste. When a butterfly’s feet come in contact with a sweet liquid, its feeding tube unfolds. Placing a slice of orange or allowing a fruit tree to drop some fruit can increase the butterflies in your garden and the tree can provide perches and shelter.
Butterflies generally fly only during the day. When it’s cloudy or night, the adult butterfly rests hanging upside down from leaves (including grass) or twigs. Butterflies can’t hear, but they can feel vibration which helps them avoid predators.
This website has a variety of useful information on butterfly gardening, including plant lists.
Butterflies, bees and other pollinators need shelter to hide from predators, get out of the elements and rear their young. Let a hedgerow or part of your lawn grow wild for ground-nesting bees. Let a pile of grass cuttings or a log decompose in a sunny place on the ground. Or, allow a dead tree to stand to create nooks for butterflies and solitary bees.
Overwintering
Where butterflies spend the winter awaiting spring depends on the species. Monarchs, as we know, go to either Mexico (from summer ranges east of the Rockies) or California (from summer ranges west of the Rockies). But other butterflies overwinter in place in one form of their life cycle, depending on the species: egg, larva, chrysalis, or adult. Some even convert their body sugars to natural anti-freeze and overwinter in a state called diapause. Here is a list of common butterflies and their overwintering phase.
A garden can produce your food with some of the same plants that attract butterflies. As mentioned earlier, fallen fruits attract butterflies, so small (e.g., berries) and tree fruit plants will attract butterflies both when flowering and fruiting. I rarely see butterflies on Solanaceous plants (peppers, tomatoes, eggplant) but often see them on various squashes and cucumber flowers. Plants such as the Umbelliferae dill and anise, mints (Lamiaceae) like true mint, basil, orgeano, marjoram, lavender, and sage provide culinary herbs and support butterflies. Although leafy herbs are not best after flowering you can let some flower and seed to self-sow and support butterflies, same with radish, and carrot.
butterfly releases are not healthy for butterfly populations
Finally, a caution about rearing and releasing butterflies from purchased chrysalises (or releasing adult butterflies for weddings and other ceremonies): DON’T DO THIS. Seeing butterflies emerge from the chrysalis is fascinating and educational but introducing species and individuals into local populations can be harmful. If you choose to buy a chrysalis to see a butterfly emerge, don’t release that butterfly.
The Xerces Society explains why butterfly releases are inadvisable.
Butterfly releases may present problems through the transfer of disease from wild habitats, laboratories, or industrial breeding facilities to other colonies, where die-off may result or diseases may just weaken wild populations and make them more susceptible to other stressors. In the past, laboratory populations of monarchs have been devastated by protozoan parasites.
Links to information and sources of nectar and host plants (some are regional so i included multiple options).
Attracting Butterflies
Nectar Plants
How to attract butterflies and hummingbirds
More nectar plants
Nectar-rich plants
Top ten butterfly flowers
Nectar plants categorized by growth habit or traits (annuals, vines, perennial herbs, flower colors etc)
Butterfly species and associated nectar plants
Host plant list
How to identify butterflies
This website from Florida has butterfly ID cues and lots of info on Florida butterflies.