A dozen years ago I saw my first Giant Swallowtail butterfly when it stopped by to nectar on the wildflowers. It superficially resembled an Eastern Swallowtail while gliding about, but once it settled on the Asclepias tuberosa, it was clear that it was not one of my regular garden visitors. The coloring was wrong and it had an unusually large wing span. I was pretty sure it was a Giant Swallowtail and just as I've read, that first sighting was dazzling!
What a beauty and the 6.3 inch (16cm) wing span makes it the largest North American butterfly.
 |
| Forewing with diagonal band of yellow spots. Tails are edged with black and filled with yellow |
The Giant Swallowtail Butterfly/Papilio cresphontes' flight is a graceful series of strong flaps and long glides. It spends its time on the wing, nectaring or patrolling for mates (if male). I waited patiently for it to stop flitting and pose prettily with wings fully spread, but, it was feasting madly.
It's welcome in most gardens, but, is considered a pest in Florida's citrus growing regions where citrus trees are its chosen host plant. Fortunately there are plenty of parts of the US and Canada where it is welcome, including here in my garden in middle Tennessee.
Back then I wasn't growing its host plant, but several years ago I bought two Hop Tree/Ptelea trifoliata hoping that the next Giant Swallowtail that visited would find a place to lay eggs.
That's exactly what happened the last two summers. This summer the two trees have hosted over two dozen caterpillars...and both trees have been defoliated. But, I am okay with that and if they don't recover, I will order another tree because the caterpillars are fabulous to watch....And maybe next year I will get to see a Giant swallowtail lay eggs.
Once they mate the female lays one bright orange egg on a host plant leaf. I found the orange eggs on several leaves and continued to find eggs and new instars every few days.
The eggs hatch anywhere from 4 to 10 days later.
There are five larval instars stages and the earlier instars are more realistic bird-dropping mimics than the later stages and are often found on the leaf surface just as you would find bird droppings. Mature larvae usually rest on stems or leaf petioles (Hagen 1999) when not eating and are more active at night for protection from predation.
They are very hungry caterpillars. Before it even emerges from its egg, the very first thing a caterpillar does is eat! Caterpillars chew their way out of its egg, and then it eats the rest of the eggshell. After that, it starts eating and eating its host plant leaves until it's molted and ready to "unzip" it's skin to reveal the chrysalis.
 |
| Until they're ready to climb away to find a place to pupate into the chrysalis stage. |
Btw, I have searched everywhere within 30 feet of the trees and have been unable to locate a chrysalis. It's late August and it's common for swallowtail caterpillars to overwinter in their chrysalis and wait until spring to emerge. Diapause, is a dormant state where the insect's development is halted to survive what ever weather is thrown at them. Where ever they are they are well hidden, so I've borrowed a photo (below).
 |
| source |
Our Wildflower Wednesday hostplant star, Ptelea trifoliata, aka, wafer ash is a deciduous small tree or large shrub in the citrus family (Rutaceae). It is native to North America, where it is found in Canada, Mexico, and the United States.
According to Illinois Wildflowers: Hoptree is not only a host plant for the Giant swallowtail butterfly but also "attracts small bees, wasps, flies and ants. These floral visitors feed on the nectar of the flowers primarily, although some small bees also collect pollen. Another specialist feeder is the thrips Neohydatothrips pulchellus, which sucks juices from the leaflet undersides. Other insects that feed on Wafer Ash include the caterpillars of the moth Yponomeuta atomocella (Brown-Bordered Ermine Moth) and the larvae of the Scolytid beetle Phloeotribus scabricollis, which bore into the bark and wood.
It's a multi-stemmed rounded, small understory tree or shrub that can be found growing in areas with calcareous soils including rocky bluffs, glades, ravines, thickets and prairies, open woodlands, and river bluffs which means it would be very happy in middle Tennessee gardens. The flowers are not particularly showy, but fruits are ornamental. Very adaptable and easy-to-grow tree which is good for both moist and dry conditions. I planted them in large containers in partial shade so that I could make sure they would get enough water to survive our extremely dry summers. Now that's adaptable.
Hoptree flowers bloom in mid-spring and are fragrant. The flowers are visited by bees, butterflies, flies and wasps seeking nectar and helping pollination.
The fruits are samaras, which is a type of dry fruit (not fleshy like a berry), each with a single seed encased in a papery covering with a winged edge surrounding the seed, designed to help the wind disperse it.
 |
| (source: Photograph Gene Sturla) |
The Particulars
Botanical name: Ptelea trifoliata
Common Name: hop tree, common hoptree, wafer ash, stinking ash, and skunk bush
Type: Tree
Family: Rutaceae (often called citrus family)
Native Range: Eastern and central United States
Zone: 4 to 9
Height: 15.00 to 20.00 feet
Spread: 15.00 to 20.00 feet
Bloom Time: May in Middle Tennessee
Flower: Fragrant, Panicle. Mostly a dioecious plant (source: Edward W. Chester, photograph) They need enough sun to flower. I might have to relocate my containers.
Fruit: Found in pendulous clusters that resemble hops.
Leaves: Trifoliate, deciduous leaves with leaflets on a petiole up to 2 inches long that will turn yellow in the fall. I am hoping that i have leaves next spring after the caterpillars defoliated my trees!
Sun: Part shade to full shade or even full shade
Water: Dry to medium
Maintenance: Low, Can handle some drought
Soil: Dry soil, Shallow-Rocky Soil
Wildlife Value: Birds and small mammals enjoy the fruits as a food source. Host plant to the larva of giant swallowtail butterfly (Papilio cresphontes). The caterpillars resemble bird droppings. Carrion flies pollinate the flowers.
Suggested Use: Hedge, Flowering Tree, Butterfly Garden, Drought Tolerant Garden, Native Garden and Winter Garden
Comments: The Giant Swallowtail is on the move. It's moving further north and further west! In the last few years it's been spotted in Los Angelos, CA and Ontario, Canada. You might want to check out this article about its migration to Canada.
Deer: White-Tailed Deer don't seem to be a problem. The leaves and twigs have an unpleasant scent and bitter taste.
Links: For a really excellent look at the hoptree in winter and its chemical defense system go to Mary Ann Borge's article.
Gail Eichelberger is a gardener and therapist in Middle Tennessee. She loves wildflowers and native plants and thoroughly enjoys writing about the ones she grows at Clay and Limestone. She reminds all that the words and images are the property of the author and cannot be used without written permission.
No comments:
Post a Comment
"Insects are the little things that run the world." Dr. E O Wilson