Aristolochia grandifolia: More to It Than Meets the Nose
It looks something like a pitcher plant, one of the Asian or South Pacific varieties of carnivorous plants that capture insects with entrapping hairs, sticky substances, and pools of water from which they cannot escape. In this case, however, Aristolochia grandifolia, the vine that produces the largest native flower in Costa Rica, also called the Pelican Flower and Dutchman’s Pipe, attracts and kidnaps the pollinating fly for only twenty-four hours, just long enough for the fly to do its job.
A plant that attracts several species of flies, including the common housefly, must produce some unusual aromas. In fact the odor emanating from essential oils, called geraniol, is quite foul, reminiscent of rotten meat. Notice the colors around the entrance to the flower—dark maroon. Attracted when the flower first opens and its vile smell is at its most potent, the fly, carrying pollen from other flowers, enters the dark passage. Then the fly cannot turn around due to the nature of the trichomes, or hairs, pushing it forward to the utricle where the reproductive organs are. The walls of the utricle produce nectar for the fly to eat while trapped. Once the pollen is delivered to the pistils and stigma, stamen are triggered to produce more pollen which falls on the fly, preparing it for a visit to another flower. There must be some signal that pollination has occurred, because after a period of time the trichome along the passage way decompose, and the fly can then climb out and escape.
The success rate is stupendous—I collect over 100 quarter-inch seeds from the mature pod of almost every flower and give many away to visitors. The seeds germinate easily.
At Finca Cántaros, this plant is part of our self-guided tour. Whenever I accompany visitors to show them these unusual flowers and explain that they smell quite terrible, I am amused to see that almost all of them, young and old, want to experience smelling the flower for themselves. “How bad can it be?” one gentleman asked. Wrinkled noses and exclamations of “ewww” or “ickkk”, always follow!
Reference: Wikipedia on Aristolochia grandifolia.
Note: Aristolochia g. is the food plant for some species of swallowtail butterfly larvae.