Jewelweed: More than Just a Gem
At the edge of the woods in my backyard I have nurtured a large patch of Jewelweed (Impatiens capensis). I can sit on my deck and see the orange and red flowers hanging on the plants like jewels. The Ruby-throated hummingbirds zip from my feeder down to the flowers and back again. A single bird can visit as many as 200 flowers in just 15 minutes.
I’ve noticed that jewelweed flowers quickly vibrate back and forth as the hummingbird’s bill probes the flowers. This didn’t seem to be very remarkable to me, but to biologist Ethan Temeles and his students at Amherst College, it was a clue for further research.
Each jewelweed flower has a tiny opening that is only about four millimeters wide, which quickly narrows to only a millimeter and bends sharply downward and then back as a spur. At the far end of the spur is the hummingbird’s liquid prize, sweet nectar.
While the bird hovers, it uses its long tongue to reach down into the flower tube. As the tongue arrives at the sharp turn in the tube, the flower is gently pushed away. The tongue extends to end of the tube, and nectar flows into channels on the tongue. The bird pulls the tongue back to drink the nectar thereby releasing the pressure on the back of the flower tube and the flower moves forward.
Temeles and his students found that the flower hangs from a very thin stem with just enough tension to make the tongue’s movements spring the flower back and forth as it pulses in and out while licking nectar. Each time the flower springs back, pollen is brushed on top of the bill and forehead of the hummingbird. When the hummingbird visits the next jewelweed flower, pollen is brushed onto the new flower to complete fertilization.