I Stand Corrected!

May 26, 2010 at 6:18 am (botany, methods, Uncategorized)
Tags: blackhaw, Mayslake, nannyberry, Viburnum lentago, Viburnum prunifolium

by Carl Strang

In a recent post I identified a shrub at Mayslake Forest Preserve as blackhaw (Viburnum prunifolium). Fortunately I have an excellent botany backstop in Scott Namestnik. In his comment he pointed to the possibility that the plant might instead be the closely related nannyberry (V. lentago), pointing to some characteristics he could see in the photo. I checked my own principal reference, Plants of the Chicago Region by Swink and Wilhelm. They emphasize two characteristics, leaf tip shape and petiole structure, that separate blackhaw from nannyberry.

Blackhaw leaf tips should be “abruptly short-acuminate,” i.e., blunt. Nannyberry leaf tips are long-acuminate, meaning that they are somewhat pinched and drawn out in a longer point, as the above photo from the shrub in question illustrates.

On the petiole, or leaf stem, nannyberry has distinct wings or flanges that are undulate, or wavy, as the photo confirms. Blackhaw petioles, if a little winged, would then be straight and not wavy.

I want to make a couple points, here. First, botanical identifications often require wading through some terminology. If you are not familiar with the terms they can be intimidating at first, but it’s simply a matter of slowing down and looking up definitions. The Swink and Wilhelm book, which I recommend for anyone serious about Chicago region botany, has an excellent glossary with drawings that make meanings clear. The only caveat is that sometimes comparisons are relative. In this example, what is the boundary between “short-acuminate” and “long-acuminate?” Here I used another tool, the Internet search. I found photos of both plants with close-ups of their leaves, and that allowed me to see the distinction.

The second point is that science works best when the scientist is egoless. This time it was easy. I had no ego invested in this identification, and I know that Scott is a topnotch field botanist. I’m a vertebrate ecologist. At the same time, however, I had the plant and all he had was a compressed photo. It was important that I go back and confirm his suspicion, both to make the correction and to learn the difference so my own botanical knowledge would be improved.

I’ll finish by pointing to Scott’s own blog, Through Handlens and Binoculars, which he and his wife Lindsay produce. It’s on the short list of blogs I follow regularly.