Thigmonasty is the term for touch-induced movement in plants. Fourvalve mimosa (Mimosa quadrivalvis) is a thorny vine that grows in dry, scrubby areas at the Oslo Riverfront Conservation Area. This diminutive but daunting vine flowers with small pink poofs about the size of a dime. Please do not confuse it with sunshine mimosa (Mimosa strigilosa), a thornless groundcover that sports showy pink poofs about the size of a nickel and prefers much moister conditions.
Each leaflet has a pulvinus, a specialized ‘motor cell’ that responds to touch. No, pulvini are not visible. The thorns on the stems and seed pods of this plant are quite visible, though …
This armored seed pod splits into four segments, when ripe, giving rise to the common name four valve mimosa and the species name quadrivalvis.
Its seeds are said to be eaten by songbirds, quail, and gopher tortoise.
Other common names include sensitive briar and cat’s claw. This plant once was known as Shrankia microphyllum.