For as long as I can remember, the unknown leggy bush sat in the swamp near the trail, languishing in the shade of a giant ash tree. Though I didn’t recognize it, I never bothered to figure out what it was since it had few leaves and no flowers. In the sunnier parts of the swamp, Lizard’s tail bloomed so profusely it was easy to ignore the bush. But then things changed…
The great Ash was attacked by the Emerald ash borer, and as it declined the unknown bush revived. It began to receive at least the minimal amount of sunlight it needed to be happy. And then in June it bloomed, likely for the first time in decades – revealing itself as a Buttonbush (Cephalanthus occidentalis). Being the only flowering Buttonbush in the entire forest (so far as I know) the fragrant globular blooms became an instant butterfly magnet. The day my fellow forest steward Kay and I happened upon it, the flowering globes were giving their nectar to two forms of Tiger swallowtail, and one Zebra swallowtail.
Years ago I rarely saw butterflies, or most other insects for that matter, in the densely shady place this forest had become. But forests change – thanks to the removal of invasive shrubs in the understory, and the death of the ash trees – the forest is now full of sunny gaps littered with the remains of big trees. As flowering herbaceous plants fill the gaps, butterflies find them. But few flowering shrubs have the appeal of the Buttonbush, whose hundreds of long-tubed blooms can be easily plumbed by a butterfly’s long tongue.
To get nectar from these aerial pincushions, butterflies must dangle upside down, holding on with their tiny hooked “tarsal claws”.
While it’s been thrilling to see so many Tiger swallowtails drifting through the understory lately, the growing presence of Zebra Swallowtails is something special. Though this forest abounds with Pawpaw, the Zebra caterpillar’s only food plant, until recently the butterflies were absent. This is the first summer I have observed them in numbers, and I’ve been waiting for it to happen.
I don’t know if they found their way here naturally or with human help – but either way they are certainly welcome. Their striking pattern suggests a more tropical origin – which is true for butterfly and food plant alike. The range maps for Common pawpaw and Zebra swallowtails match perfectly, and though Kentucky is smack in the middle of the range, both species have more numerous subtropical relatives.
Speaking of foodplants, the Buttonbush shines in that department as well – its foliage feeders include the larvae of the Promethea moths (Callosamia promethea), smartweed caterpillars (the smeared dagger moths, Acronicta oblinita), beautiful wood-nymph larvae (Eudryas grata), and hydrangea sphinx moth larvae (Darapsa versicolor).
All the more reason to grow it. This year we planted ten 3 gallon Buttonbushes in various moist sunny places in the forest. As those wetland gaps continue to open up, next year we’ll plant a lot more. And apparently this shrub doesn’t require wet soils to be happy, just not really dry ones – so you too can grow your very own Buttonbush.