The Sensitive Plant: Mimosa Pudica
I didn’t touch a sensitive plant (mimosa pudica) until long after I’d first read about it—but since that initial introduction, I’d been waiting a long, long time to meet one. To use the word carefully, we know by now that plants are intelligent—they learn from their experiences, solve problems, protect each other. Though the sensitive plant’s movement might not indicate this specific type of sentience, it's a good and immediate visual symbol of plants' ability to communicate. You touch the plant and, like skin, it reacts.
Sometimes called the sleepy plant or shy plant, mimosa pudica is part of the pea family, native to South and Central America and now a pantropical weed, found in India, Malaysia, Philippines, Japan, Thailand, Bangladesh, and Jamaica. When you stroke or tap the leaves, they’ll fold in on themselves and droop low, only to open again a bit later. When touched, the plant releases potassium ions, forcing water out of its cells, reducing the cells’ pressure and causing them to collapse. (The plant will also close its leaves at night.) Scientists speculate that this process might be, partly, to fend off herbivores; it can also dislodge insects. It takes a significant amount of energy from the plant to do it, and it cannot photosynthesize in this stage. It is hard work to be shy.
When the leaves close, you’ll see the thorns along the plants’ spine (when they compete with tropical crops, these tender beauties can actually be considered invasive). I did not notice the thorns when I finally touched a sensitive plant at the The Huntington Library, Art Collections and Botanical Gardens in Los Angeles. It was early spring; if it was June, I would’ve seen the soft, fluffy pink flowers that bloom along the mimosa pudica in the summer. I tapped it, pet it as if it were a kitten, thinking all the while about Bernard McMahon’s thoughts on the shy plant in The American Gardener’s Calendar, published in 1806. “The sensibility of this plant is worthy of admiration,” he wrote, “…the leaves just like a tree dying, droop and complicate themselves immediately…so that a person would…think they were really endowed with the sense of feeling.”