From the Photographer...
Do you remember KOOSH balls? Popular toys from the late 1980’s made out of rubber band-like strings? If you can picture a pink KOOSH ball about one inch across, that’s essentially the flower of one of the strangest plants in the prairie.
Sensitive briar (Mimosa nuttalii, aka cat’s claw, sensitive plant and mimosa) grows in grasslands in the central United States, and has close relatives elsewhere in North America. Besides its small pink KOOSH-like flower, the native legume has a number of other distinctive features. The “sensitive” part of its name comes from its ability to close its leaves when touched or when jostled around by wind. No one is sure what advantage this gives the plant, but some likely explanations are that it helps deter insects from eating it and/or that it helps conserve water on hot windy days.
If nothing else, the folding leaves can be a great distraction for kids on a prairie hike, but don’t show them the trick if you’re in a hurry to get someplace…
Those sensitive leaves are arrayed on long branches that sprawl along the ground, giving the plant a big footprint — up to 6 feet or more in diameter. Each stem is covered with small sharp spines. Even the seed pods, which resemble green beans in size and shape, are spiny. The spines on the stems all point toward the base of the plant — presumably to make it uncomfortable for large herbivores to strip the leaves off the stems with their mouths. However, I once watched a cow do just that, with no apparent ill effects, so it’s not a foolproof strategy!
I photographed this sensitive briar flower in a small, restored prairie in my hometown of Aurora, Nebraska. While this photo doesn’t show the foldable leaves, you can easily see the numerous spines on the stems. The yellowish highlights on the pink flower are the pollen grains, which stick to the numerous pollinators that visit this plant.
Chris Helzer is program director for the Conservancy's Eastern Nebraska Project Office and the author of the book The Ecology and Management of Prairies in the Central United States. His images of Nebraska prairies and their wildlife are among the most spectacular in the Conservancy's archives. See more of Chris’ photos on his blog, The Prairie Conservationist.
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