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Native plant woos spicebush butterfly caterpillar

A few weeks ago, I was watering a young and struggling spicebush plant and noticed that most of the foliage had disappeared.

I chalked it up to a droughty month and little time to water. On closer inspection, I found four intact leaves, margins neatly folded together. Gently peeling apart one of the leaves, I peeked inside: two giant yellow eyes stared back at me.

Be still my heart: a spicebush butterfly caterpillar! Finally I had come face-to-face with the object of a years-long pursuit.

This may be the highlight of my 2009 gardening year.

I immediately constructed a 4-foot-tall rebar teepee, swathing it with white row cover to protect the caterpillars from becoming bird food. Thank goodness I don't live in a neighborhood with an architectural review board - I can only imagine the consternation this contraption would elicit.

I have long been attracted to this caterpillar's clownish looks - lime green body, two sets of bright yellow "eyes," small blue dots along the sides of its body. The "eye" spots aren't really eyes but a protective device designed to scare off predators.

But before the caterpillar achieves its comic facade, it looks more like a splat of olive-green bird poop decorated with a few white splotches. This caterpillar couture blends perfectly with the leaf on which he is dining. As the caterpillar grows, it wraps itself in a leaf that provides food as well as protection.

Butterflies are very picky about where they lay their eggs, selecting specific host plants that newly hatched caterpillars will eat. I have had an occasional adult spicebush butterfly visit my zinnias so I knew that one of its two preferred host plants - sassafras and spicebush - lived in the area.

Most people are familiar with sassafras, a native shrub, with its distinctive foliage: mitten-shaped, three-lobed or whole, all on the same plant. But spicebush is not so familiar. I happened to find one at a local garden center five years ago, planted it, and then spent the next four years watching and waiting for caterpillar activity.

Nothing happened.

Obviously something was amiss, so I did more reading and discovered that spicebush butterflies lay eggs only on the native form of spicebush, Lindera benzoin, not the Japanese form, Lindera strychnifolia, I had planted. I had not understood the difference.

Yes, they look very different - one is deciduous with plain looking foliage; the other is evergreen with jazzy heart-shaped foliage. One attracts spicebush butterflies; the other does not.

A native plant is one that is indigenous to North America. I learned from my pursuit of spicebush swallowtail caterpillars that native plants and native insects have co-evolved - the one depending on the other to carry out its life cycle.

Discussions about the desirability of native vs. exotic species have been around for a long time but have become more insistent in the last few years as more wildlife habitat succumbs to development. Douglas Tallamay, professor of entomology and wildlife ecology at the University of Delaware, describes the need to increase native plant biodiversity and how to do it in our personal landscapes in his new book, "Bringing Nature Home" (Timber Press).

I embrace both sides of the native versus non-native plants dialogue, aiming to strike a balance in my new landscape. I continue to be a sucker for new plants, even though most of them do not support native wildlife. But now I find myself researching the native option when I have empty spaces, especially if shrub selections are involved.

So the hunt is on for another native spicebush and a few more sassafras: I want to be prepared for next year's crop of spicebush caterpillars.

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