1. Lilacs are one of the many plants on the menu for eastern tiger swallowtail butterflies.

    Gardeners tend to have a thing for swallowtail butterflies.  Likewise, swallowtails tend to have a thing for certain plants – and certain gardens. The more you incorporate their favorites into your garden, the more they will favor you with their flighty visits.

    Adult swallowtails of all species (including the half-dozen or so species native to eastern North America) share similar tastes in nectar.  A border brimming with coneflowers and sages and butterfly weeds and their relatives will have them all aflutter, as will a planting of shrubby favorites such as rhododendrons and buddleias.  Swallowtail caterpillars, on the other hand, are much fussier eaters, with each species following a specialized diet restricted to a narrow menu of plants.  As a result, swallowtails are particularly keen on gardens that include their favorite larval foods.

    Most swallowtail caterpillars confine their munching to species from one or two plant families.  Some swallowtail species thrive on both introduced and indigenous plants, whereas others require natives-only fare to thrive.  Know their preferred larval food sources, and you’ll know what to plant in your yard to transform it into a swallowtail haven.   You’ll also know which plants to examine for the large colorful caterpillars, which in their early stages resemble animated bird droppings.  Some leaf damage may also be noticeable, but it’s a modest price to pay to become the neighborhood’s most desirable swallowtail destination.

    Swallowtail Caterpillar Host Plants

    Eastern Tiger Swallowtail

    Eastern tiger swallowtail butterfly feeding on pentas. (Image by Jessie Keith)

    Many native and exotic trees and shrubs from the olive, rose, laurel, birch, and magnolia families host the large green caterpillars of tiger swallowtail, which sport two prominent eye-spots.  Before pupating, the caterpillars turn from green to brown. Tulip tree (Liriodendron tulipifera), lilacs (Syringa spp.), river birch (Betula nigra), and sassafras (Sassafras albidum) are among the outstanding ornamental plants on the menu, as are:

    Eastern tiger swallowtail caterpillar before pupation. (Image by Scott Robinson)

    Sweet bay magnolia (Magnolia virginiana).  Native to eastern North America, this small, elegant, gray-barked tree has glossy-green, deciduous or evergreen leaves with silvery undersides.  Scatterings of cupped, sweet-scented white flowers sporadically appear from late spring through summer.

    Fringe tree (Chionanthus virginicus).  Clouds of fragrant, fleecy white flowers veil the spreading branches of this large shrub or small tree in late spring.  Conspicuous blue fruits ripen in late summer on some plants (particularly if a pollenizing companion fringetree is nearby).

    Eastern Black Swallowtail

    Female eastern black swallowtail lays her eggs on plants in the parsley family. (Image

    Showy, yellow-and-black-banded caterpillars feed almost exclusively on plants from the parsley family, including dill (Anethum graveolens), parsley (Petroselinum crispum), carrot (Daucus carota ssp. sativus), and fennel (Foeniculum vulgare) .   Bronze-leaved forms of fennel  are especially effective

    An eastern black swallowtail feeding on fennel. (Image by Jessie Keith)

    ornamentals, their dark, filigreed leaves making a smoky contrast to bright-flowered annuals and perennials.  Also outstanding for foliage effect are the various species of Peucedanum such as giant milk parsley (Peucedanum verticillare).  This short-lived perennial forms large lush hummocks of deeply divided foliage, which give rise to towering, purple-stemmed sprays of lacy white flower clusters.  Most Peucedanum expire soon after flowering, but they usually self-sow (so be sure to leave some seed heads!).

    Spicebush Swallowtail

    Spicebush swallowtail larvae feed just on spicebush. (Image by Magnus Manske)

    A dark-hued butterfly that somewhat resembles black swallowtail, spicebush swallowtail is one of several reasons to grow the shrub after which it’s named.  So, too, are the boldly eye-spotted, green to orange-yellow larvae that browse spicebush’s fruity-scented foliage in summer.   One of the earliest-blooming native plants, spicebush (Lindera benzoin) decks its branches with tufts of acid-yellow flowers

    Spicebush swallowtail caterpillar (Image by Greg Schechter)

    in late winter and early spring, before the leaves emerge.   Bright red fruits and brilliant yellow fall foliage bring the growing season to a colorful close.  Spicebush swallowtail’s other favorite host is sassafras – the only eastern North American representative of the laurel family (Lauraceae) other than Lindera benzoin.

    Pipevine Swallowtail

    The pipevine swallowtail has showy blue lower wings.

    If outlandish black caterpillars with orange spikes and centipede-like “legs” appear on your Dutchman’s pipe vine (Aristolochia spp.), you have the honor of a visit from this singular swallowtail species.  With luck you’ll also witness the adults, whose blue, iridescent wings are among the showiest in the butterfly tribe.  The larvae thrive only on North American species of Aristolochia, dwindling away if raised on exotic Dutchman’s pipes such as Aristolochia elegans.  Two twining North American natives – Aristolochia macrophylla and A. tomentosa –make excellent climbers for locations where their

    A pipevine swallowtail caterpillar feeding on pipevine. (Image by Jessie Keith)

    wide-ranging roots have room to spread (both are hardy from USDA zones 5 to 9).  Their rapidly ascending stems with heart-shaped leaves emerge from the ground in spring and lengthen to 20 or 30 feet within a few weeks.  Curious, contorted, tubular flowers with flared tips appear in the leaf axils in early summer.  Most other North American Aristolochia species are lower growing perennials that spread underground to form large clumps.  Virginia snakeroot (Aristolochia serpentaria) functions nicely as a deciduous groundcover for informal garden areas in sun to light shade.

    Eastern Giant Swallowtail

    Citrus are the favorite host plant of eastern giant swallowtail.

    Native or exotic species from the citrus and rue family (Rutaceae) entice this enormous, black, yellow-banded butterfly, whose wingspan can reach 6 inches.  Gardens that are too cold for the likes of lemons (Citrus limon) and oranges (Citrus aurantiaca) can opt instead for one of the several cold-hardy Rutaceae species that host the blotchy, black and white larvae.  These include hop tree (Ptelea trifoliata), a medium to large shrub from central and eastern North America with handsome, three-parted leaves and small, fragrant, late-spring flowers.  Rounded, wafer-like fruits develop in late

    The eastern giant swallowtail caterpillar.

    summer.  Its cultivar ‘Aurea’ – with glossy, chartreuse-yellow leaves – is one of the most striking foliage plants for temperate gardens.   Swallowtail hosts for the perennial border include gas plant (Dictamnus albus), which bears showy spires of white or purple flowers in late spring on bushy, 3-foot-tall mounds of leathery, rich-green foliage.  Native to Eurasia, it lives to 50 years or more in gardens.  Warning: contact with plants in the rue family can trigger severe dermatitis in susceptible individuals, although such cases are rare.

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    About Russell Stafford


    Hortiholic and plant evangelist Russell Stafford transplanted his first perennial at age 7, and thereby began a lifelong addiction. He is founder, owner, webmaster, nursery manager, propagator, shipping and telemarketing supervisor, data entry specialist, custodian, and all other positions at Odyssey Bulbs (and Odyssey Perennials), an on-line micronursery specializing in cool and uncommon plants. He also works as a plantsman and horticultural consultant specializing in the naturalistic and the obscure, and as a freelance writer and editor. He formerly served as curator and head of horticulture at Fernwood Botanic Garden in Niles, Michigan; as horticultural program coordinator at the Center for Plant Conservation (then located at the Arnold Arboretum in Jamaica Plain, Massachusetts); and in various other horticultural capacities. His academic degrees include a masters in forest science from Harvard University. He lives, works, and plays with plants in South Lancaster, Massachusetts. Russell is a former editor at www.learn2grow.com and a frequent contributor to gardening magazines including Horticulture and The American Gardener.

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