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Butterfly GardensBy Victoria Parsons

Anybody can plant a butterfly garden with beautiful blooming flowers – but people who plant food for caterpillars will have butterfly factories.

The gulf fritillary is one of the most common butterflies in the Tampa Bay region. Its caterpillars require passionflower. In fact, the most spectacular butterfly garden in the world will be deserted and empty unless there is food for their caterpillars nearby. “Caterpillars are truly specialists,” notes Kristin Gilpin, manager of the BioWorks Butterfly Garden at the Museum of Science and Industry. “Butterflies can nectar on many kinds of flowers, but caterpillars require one or two very specific plants and cannot survive without them.”

That challenge has made MOSI’s butterfly exhibit one of the few in the nation where the star performers are born onsite rather than purchased from breeders. With assistance from a dozen or so dedicated volunteers, Gilpin grows larval food for native caterpillars that are then captured and placed inside a specially cooled area where they are protected from predators as they transform from caterpillars to chrysalises, and finally to the butterflies that flit through the exhibit’s indoor butterfly encounter.

Caterpillars More Challenging Than Butterflies
Part of the reason that people who plant butterfly gardens don’t plant caterpillar plants is simply lack of knowledge. “When you stop and think about it, of course butterflies and caterpillars don’t eat the same food, but many of the people visiting the BioWorks gardens just don’t know the difference,” she said.

Another part of the problem is that it’s much harder to find caterpillar food in a “big box” garden store. Caterpillars have been around for thousands of years, so many of the plants they need may be considered weedy. And even when an attractive larval food like butterfly milkweed is available, it may be treated with pesticides to kill caterpillars because they chew up leaves and flowers.

Zebra longwing caterpillars live on passionflower too. They prefer shady spots while the gulf fritillary favors leaves growing in sun. “We plant a lot of the caterpillar food in the back of the garden where the damage is less likely to be noticed but it’s very rare that plants are seriously damaged,” Gilpin said.

In some cases, caterpillars have evolved from eating relatively rare native species to more common plants and gardeners may unintentionally destroy an entire generation of butterflies by treating plants with pesticides. Giant swallowtail butterflies, for instance, require native Hercules club (seldom planted intentionally because of its ferocious thorns) as larval food but have grown to eat citrus, particularly the new growth that flushes just after the tree has been fertilized. When homeowners see large caterpillars that look more like bird droppings than baby butterflies damaging their citrus trees, it often prompts them to dowse the tree in pesticides.

The charming “Uncle Sam” or polka-dot moth wasp – which is really a butterfly – is thought to have extended its range when it switched larval food from a practically unknown beach vine to the now-ubiquitous oleander introduced by colonists in the 17th century. Large numbers of caterpillars with tufts of black hair on bright orange bodies are not poisonous although they do resemble stinging caterpillars. And while they can transform a healthy oleander into skeletal remains practically overnight, they are not likely to kill the plant.

A successful butterfly garden is a wonderful thing, but growing plants for caterpillars is even better, Galpin said. “You’ll have many more butterflies because they seldom venture far from their larval food even as adults – and you’ll know that know that your efforts have played an important role in their very existence.”

Top Four Plants for Caterpillars

The zebra longwing is the state butterflly. It's an extraordinarily long-lived butterfly that often frequents the same flowers day after day. Whether you have a butterfly garden or not, here are Gilpin’s top recommendations for hosting native caterpillars:

Butterfly Milkweed (Asclepias spp.) is the favored food for both monarch and queen caterpillars although Tampa Bay residents are most likely to see monarchs because they tolerate urban settings better than the queens. Milkweed is also the plant most likely to be found in major garden centers and sometimes they even come with caterpillars already growing on them. (If they do, try and make a point of telling the garden center manager how much you appreciate the opportunity to buy
baby butterflies.)

Senna comes in a wide variety of species including the candle bush shown here. It is the larval food for the cloudless sulphur butterfly. Butterfly gardeners who plant milkweed will have monarchs in their yard nearly year-round because they don’t travel far from their larval food sources. They prefer temperatures between 60 and 80 degrees, though, so populations are likely to be higher in Spring and Fall months.

Milkweed comes in a variety of colors and shapes, including a vine and a giant version. They prefer sun but will tolerate shade. Along with monarch caterpillars, they attract aphids and stink bugs. Most experts recommend washing the insects off the plant with a strong spray of water, but they may need to be destroyed by hand if caterpillars are present.

Monarchs typically prefer only the new growth for their caterpillars but cutting a milkweed back will almost always result in a flush of fresh leaf. If you remove growing tips, they can be pushed into damp soil and left in the shade to root new plants to share with friends or feed even more caterpillars.Experts can often identify caterpillars without seeing them by knowing what plants they are eating. This caterpillar on a senna plant will become a cloudless sulphur butterfly.

Passionflower (Passiflora spp.) is the larval food for both zebra longwings and gulf fritillaries. Longwings, the state butterfly, are also among the most long-lived, surviving six to nine months in Florida. They tend to live in small social groups and often can be seen nectaring from the same flower at nearly the same time of day for several weeks or months. The gulf fritillary is one of the most common butterflies in Tampa Bay. Its striking bronze or orange coloring resembles a monarch but it’s a much smaller butterfly.

Typically, the longwing butterflies will use the passionflower growing in the shade while fritillaries prefer the sun. Caterpillars may visibly damage a small passionflower in the early spring, although they cause little damage once the plant is Polydamas and pipevine swallowtail both use the pipevine as their larval food.growing well. Be careful where you plant it, though. Passionflower is a native plant but it grows very quickly and can take over a small yard.

Various species of cassia (Senna spp.) offer gardeners spectacular flowers on a seasonal basis while serving as the larval food for several butterflies including both the clouded and cloudless sulphur (cloud refers to the black edging on the wings), orange sulphur and the little sulphur. The show-stopping candle bush is a senna, as is the long-blooming winter cassia which is covered in bright yellow blooms even in cold weather.

The cloudless suphur requires senna as its larval food but enjoys passionflower for its nectar. Like milkweed, having a senna plant in your garden also ensures a year-round population of sulphur butterflies but the senna is seldom damaged.

Finally, Galpin recommends growing pipevine (Aristolochia spp.) for both the polydamas swallowtail and the aptly named pipevine swallow tail, one of the few blue butterflies found in the Tampa Bay region. Like monarchs, these butterflies prefer to lay their eggs on new growth and they can totally defoliate even a healthy plant. But like milkweed, the pipevines quickly recover and can handle several generations of caterpillars every summer.

But Don’t Caterpillars Sting?
Around the world, very few butterfly
caterpillars actually sting. In Florida, the only
poisonous caterpillars are larval moths not
butterflies. They don’t have stingers but
their spines are connected to poison glands.

None of the caterpillars described in this
article are poisonous stingers, although
some have hairs that mimic the poison
species to protect themselves from predators.

Click here for more information.

The larva of a
polydamas swallowtail looks quite ferocious
but doesn't sting.

More Resources
The Southwest Florida Water Management District, which sponsors the BioWorks Butterfly Garden at MOSI, has developed several outstanding publications on gardening for butterflies and caterpillars. E-mail Gilpin for a PDF copy at kristeng@mosi.org.

Other Web Resources Include:

Kris Gilpin’s blog that covers all things butterfly, including caterpillars, at http://lepcurious.blogspot.com/
The University of Florida’s extensive documentation on Florida butterflies, including larval food
requirements at http://edis.ifas.ufl.edu/UW057
Florida Atlantic University’s brochure on butterflies and caterpillars has less information but great
photos: http://riverwoods.ces.fau.edu/Education/ButterfliesandCaterpillars.pdf

And every serious caterpillar gardener needs the definitive book on the topic, Florida Butterfly Caterpillars
and Their Host Plants, by UF professors Marc C. Minno, Jerry F. Butler and Donald W. Hall.
Local sources for larval food plants include Kirby’s Nursery in Seffner and Wilcox Nursery in Largo.
For more specific plants, visit Lukas Nursery in Orlando (www.lukasnursery.com) or the Association of
Florida Native Nurseries at www.afnn.org.

Most photos on these pages are courtesy of the Bugwood Network, www.bugwood.org.