Saturday, July 26, 2008

An unexpected flower

Crape myrtles (Lagerstroemia indica) are everywhere in the Southern U.S.; they're used (overly so) as street trees, in home landscapes, in commercial landscapes, etc. Brought to the Carolinas by botanical explorer Andre Michaux, they're attractive in flower, have lovely bark and architectural shape, and are TOUGH.

But, I've never thought too much about them, because I haven't see many insects or birds using the flowers or eating the fruits or seeds. They weren't high on my 'plants that work for a living' list.

But checking plants near the potting bench this morning, I kept hearing a couple of hummingbirds twittering and whirring high up in the crape myrtle nearby. Were they eating small insects attracted to the flowers? Were they annoyed with me because I was near one of 'their' feeders?

What's going on with crape myrtle flowers anyway?

First I checked for nectar (none), then looked at some open flowers, and noticed a couple of honeybees collecting pollen at the center of the flower. A few Google searches later, and I found out that Lagerstroemia flowers produce two kinds of anthers (the pollen-producing structures), the fertile 'real' pollen is produced by the longer peripheral anthers, with the 'attractant' pollen produced by the central clusters of anthers.

One of my 'hits' was a research paper that had determined that the composition of the two pollen types was different too, the 'real' pollen being higher in sucrose, whereas the 'food' pollen had a balanced amount of glucose and fructose. These researchers (this was an abstract from a 2003 article in Plant Biology) looked at lipid composition, too, but I wasn't able to read the full paper online.

I also 'hit' on an interesting site that has most of Charles Darwin's correspondence posted.

He exchanged letters with almost 2000 people during his lifetime. Apparently, Joseph Dalton Hooker (a notable botanist of the time) had given Darwin a Lagerstroemia indica, suggesting that he'd find the flowers interesting. And Darwin had indeed, corresponded with a botanist at the Royal Botanical Garden at Kew about the flowers.

Looking at the flowers again, I saw a small bee collecting pollen from the fertile anthers, the hummingbirds were still up in the tree, and I had a totally different perspective of an 'ordinary' garden flower.

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