A smooth leaf here, coarse bark there, fuzzy stem over there — it’s fun to touch the plants as you go through the forest, experiencing the various textures. But usually the plants don’t respond noticeably to our touch — they seem not to be aware of our presence. Mimosa microphylla, sensitive briar, is a rare exception. Brush the leaves and they fold up instantly. They also close up on cloudy days and after the sun goes down. But why? Is this just an anomaly, or is there some function to this curious behavior?
Sensitive briar is found in grasslands, on roadsides, and generally in open areas. According to The Prairie Ecologist, the plant folds its leaves to avoid being grazed. Folded leaves all but disappear, leaving what looks like a potential mouthful of briars — not too yummy! But oh, so pretty! Sensitive briar is a member of the bean family, maybe not immediately evident unless you know that the mimosa tree (Albizia julibrissen), too, is in that family. The two flowers look a lot alike. But the tree doesn’t have that wonderful leaf-folding characteristic and it’s an invasive exotic in many states, being a native of Asia. Not nearly as much fun to discover!