Field of Science

Friday Fabulous Flower - Cardinal Flower

This Friday's fabulous flower is Lobelia cardinalis, cardinal flower, although other than its scarlet color, it doesn't resemble a bird at all. The plant is usually about a meter tall, and in the late summer a stand of cardinal flower can make a pretty spectacular display rising above their favorite roadside ditch betraying their preference for wettish places. Like many bright red flowers these are displayed turned slightly upward, without any noticeable scent, and a goodly amount of nectar. Floral biologists anywhere recognize this suite of traits as indicating bird pollination. Distributed widely across eastern North America, the sole pollinator is the ruby-throated hummingbird. It may be that when the cardinal flower finishes flowering at the northern end of its range, that's the signel for hummingbirds to begin their migration southward. Lobelia's in general have flowers with a strong bilateral symmetry, and cardinal flower is no exception, with three corolla lobes out front showing the way to the tube of nectar. Two small corolla lobes curve to the side, sort of staying out of the way. The stamens are fused into a tube at the top through which the style and stigma grow and eventually emerge. Before the stigma opens a ring of bristly hairs encircling the style just below the stigma look a bit like a small bottle brush. When a hummingbird makes contact with the staminal tube and pushes it back just a little, this causes the stationary and bristly style to push pollen up and out of the tube, and action that has been called a "pollen pump", but to me it's a test tube and brush. Try it; you can actuate the mechanism yourself. These flowers are in the pollen dispersing phase. After the flower finishes its pollen dispersal, the stigma opens, the bristles fold back to trap any self pollen remaining, and the flower is ready to accept pollen from the next hummingbird to visit.

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