Saturday, August 23, 2008

Oddball Flowers

I have an admitted weak spot for the oddballs. If it catches bugs, has flowers that look like they came from some other planet, or some obnoxious-but-harmless quality, I have to grow it! This week one of my favorite oddballs is in full bloom: Stapelia hirsuta. Although the plant looks superficially cactus-like, it's actually an African member of the milkweed family, which in addition to milkweeds, also includes Ceropegia ("string of hearts"), Sodom's apple and Hoyas and Stephanotis. Though these plants look quite different, what unites them is their opposite leaves (though Stapelias have dispensed with the leaves), and five petaled flowers with a uniquely complex structure, in which insects' legs become caught in a groove in the center of the flower. The only way they can get free is to pull their foot through the groove. As they do, a pair of pollen sacs are attached to the foot. Later, they repeat the process on a receptive flower, and the pollen sacs are left behind and pollination has been achieved. If successful, the other clearly common characteristic will emerge: a seed pod that splits to release hundreds of dark teardrop-shaped seeds, are boren away on white silky parachutes.

What sets the Stapelias and their relatives apart, besides their lack of leaves, is their large to very large starfish-shaped flowers. For a couple of weeks, the buds slowly swell, balloon-like, until one day they pop open...and when they do, the second outstanding feature of Stapelia becomes apparent: they smell like rotting flesh or excrement. In the deserts of Africa where they live, flies are more in abundance than bees, so they are a good vector to take advantage of. Even the flowers' color and texture mimics a dead animal in various states of decomposition; some smell like an early stage while others smell like something that has lingered under the hot African desert sun for a week or so. This attracts carrion flies who arrive both in search of a meal and to deposit their eggs. The one in the photo here will get no meal, only frustration, because the flower will give it nothing in return for its visit. The larvae of those who are sufficiently duped to lay their eggs on the flower suffer a crueler fate - they hatch out, crawl around in search of their sustenance, and finally die of starvation.

1 comment:

yuan said...

very intersting...so it is a beauty killer? hahah...