Mimosa-pudica-flower

Mimosa Pudica: It’s the Shy Ones You Should Look Out For

Deep in the forests of Madagascar, there lives a legendary tree called the “tepe.” Perhaps you’ve heard of it before. With a thick textured trunk and leaves of an agave plant, it has voracious tendrils sprouting and thrashing from the crown like a nest of angry vipers. If you draw too close to the intoxicating aroma of its nectar, you’ll get tangled in the lashing branches, drawn into the plant’s maw, and swallowed whole.

It was first reported by Karl Leche, a German explorer who wrote to the press in 1874, dubbing it the scientific name Crinoida darjeeana, describing the plant as one used in a sacrificial ritual by the native Madagascar people, reminiscent of the rituals described by colonialists in the Americas in the previous century.

In 1935, however, one L. Hearst was fascinated by the report and went back— and found it: a tree matching the description of Karl Leche. He took several pictures, but when his colleagues disparaged his findings as inconclusive, Hearst returned to Madagascar to collect more evidence.

For undisclosed reasons, he never returned alive.

Mimosa Pudica leafs

Since then, there have been no reported sightings of this plant in Madagascar. Some say the plant slowly went extinct when explorers traipsed over their saplings, while others say it’s simply scarce. Even to this day, society has an overwhelming fascination with carnivorous plants, with countless stories of people lured into the clutches of predatory vegetation; some popular conceptions being Audrey II of the Little Shop of Horrors, similar stories by John Collier and H. G. Wells, and D&D monsters like the Alraune (who disguise as people to devour their bodies and memories).

There’s a deep-seated fear that we’ve become too comfortable with our sense of taxonomical world order, so much so that we won’t notice the day it’s swept out from under our feet.

Well.

Not so with the moving ground-cover plant, Mimosa pudica.

Where people developed a horrifying imagination around predatory plants, this feather-fronded vegetation seems nothing more than a novelty. Its scientific name roughly translates to “mimicking” (mimus) and “shy” (pudica); this is because it folds up when it feels attacked or threatened, much like a turtle jerks back into its shell or a shy kid folds in on himself when a stranger talks to him at school. Thus, it’s no surprise the plant is commonly known as the “Sensitive Plant,” the “Shy Plant,” or “Shame Lady,” amongst similar names. Even the most adventurous mythologies surrounding the plant discuss the plant as a woman fleeing the attentions of a man.

Painted as an innocent creature that pulls back in the simple effort to survive, not even the most imaginative individuals have thought of shrouding this plant in the same kind of horror as carnivorous plants.

But if you think about it, this plant isn’t shy; people attribute personalities to other plants through stories and myths, but the “Shy plant” is considered meek because it responds directly and openly to those around it. The key word isn’t “shy” but “mimicking.” The notable aspect of this plant is that it copies animal behavior.

For context, the drink “mimosa” is called such because it mimics the color of the Mimosa tree [Acacia dealbata], whose leaves look a bit like this plant’s (the Silk tree, Albizia julibrissin, is also called “Mimosa” and shuts at night much like those in the species). These plants deserve separate attention; I won’t get into it here.

Watch, and you’ll notice this plant is a summer sweetheart, carrying around purple pom-poms and reacting animatedly toward the people around it. Despite its pretense of mild temperament, mimosa pudica hates being in anyone else’s shadow and tends to push other plants around.

For context, mimosa pudica is a crop weed that thrives in full sun, USDA plant zone 7, growing up to 30 cm tall. You can tell how old it is by how enthusiastically it holds up its leaves.

Flower-Sensitive_Plant_Mimosa-pudica

In a way, its name is misleading, and so is the persona that comes with it— as is the reassurance that comes with the assumption that the mimosa pudica doesn’t pose the same threat that grips people in discussions about carnivorous plants like the Venus Fly Trap.

But I’m getting ahead of myself. By all fronts, the mimosa does seem like a rather unassuming plant. Originating from Central to South America, it’s a member of the pea family (Fabaceae), and, while considered a local weed (like vetch in colder climates), it follows other members in its family through a process called nitrogen fixation, enriching the soil in which it sits.

A word on nitrogen fixation. Burkholderia or Cupriavidus (we’ll call them Burks) are bacteria that can “fix” abundant airborne nitrogen in the soil. Because nitrogen is essential to the proper function of chlorophyll (and therefore growth and reproduction), but plants cannot use airborne nitrogen, Burks are essential to a vegetative ecosystem. Thankfully, some plants (like members of the pea family) can inhabit Burks, giving them an environment to perform this process.

Due to the structure and enzyme activity of their roots, several members of the pea family, including mimosa pudica, also prevent erosion, conduct phytoremediation (ie. stabilize toxic pollutants like hard metals from the soil), and release quite a bit of potassium when they decompose. Because this plant lives happily in arid, scalped, or disrupted soils, it’s often used for soil remediation and clean-up.

The plant is quite prolific as well. Unlike summer cheerleaders, mimosa pudica can be cloned by chopping off one of its limbs and placing it in a rooting hormone (as the plant propagates by node). More commonly, the plant spreads by seed, which sprouts just as quickly as other pea family members, at 14-21 days.

Mimosa pudica‘sdefense system is rather similar to other plants. Like raspberries, the stalk and petioles fashion threadlike prickles; its hard seed coats germinate only in warm to hot climates. The plant also wards its predators through toxic alkaloids like tannins (found in oak) and mimosine, which acts like an immune system for the plant, causing foreign cells of infectious bacteria or predatorial insects to self-destruct (this effect is called “apoptotic”) which prevents growth (“antiproliferative“).

Despite the extensive defense system, the plant has several pests. While the leaves defend themselves through rapid movement, this does not, ironically, work for the slow-moving, web-weaving pests that wrap and fossilize the leaves (like the spider mite, the mealybug, and the webworm), whose attack goes undetected.

Often, people spray plant-friendly/insecticidal soaps on the leaves. Still, these pests are tiny and frequently miss the mist, repopulating quickly (the soap destroys cell membranes, but the soap doesn’t affect them unless they’re hit). A good way to quell an infestation completely is to isolate affected plants in quarantine and spray them frequently until the infestation does not reappear for two weeks.

And like other alkaloids, people have used them to their advantage (think caffeine). In the case of mimosine, it works as an antibacterial, antiviral, and antifungal treatment for wounds and cuts. Because it’s apoptotic, some people have used it as birth control, and recent studies focus on the prospect of using extracts in cancer treatment.

These uses are especially appealing because of the consumptive benefits of the plant. Apart from its high vitamin and mineral content, Mimosa pudica is anti-inflammatory and antioxidant (golden boys of the health industry), which aids anything from joint pain to swelling, gastrointestinal issues, blood pressure regulation, or menstrual struggles. (Fun fact, where mimosa pudica serves as birth control for women, it supposedly increases fertility in men due to the aforementioned benefits.) It even boosts mood (purportedly) by intervening with hormonal receptors like serotonin and dopamine, easing symptoms of anxiety and depression, which can improve memory and reduce the effects of insomnia (much like with the adaptogenic qualities of gotu kola).

Despite the benefits, it’s important to remember that the alkaloids in Mimosa pudica are still considered toxic to people in large quantities (people don’t usually recommend consuming more than 15-20 ml depending on body weight). Some people make topical pastes or tinctures (1-3ml). One way to take in mimosa pudica without risk of overdose would be by putting a couple of leaves in tea.

Even the rapid movement characteristic of Mimosa pudica might not be that unique. Thigmonasty (responsive movement to touch) is another common characteristic of the pea family. Common pole bean shoots rapidly climb poles (pole dancing) until they can no longer “feel” the pole, at which point they straighten out and try again; the telegraph plant rapidly taps its apex leaves in response to specific sounds. A subfamily, Loasoideae, moves its flower stamen toward the center of the plant when it wants to spread its pollen onto an insect or self-pollinate. Other families adapted to move as well, from the wood sorrel family to the aforementioned carnivorous plant varieties, all using similar mechanisms (for now, we’ll keep phytoplankton out of the equation).

If its defense mechanisms and health benefits tightly coincide with other plants and relate to others in its family, perhaps the attention toward this plant isn’t on motion, but on the way it moves. Sure, plants like the pole bean can move rapidly and responsively. But people focus on mimosa pudica for the same reason that people have been fascinated by Venus Flytraps and Sundews— it responds directly to people in a way directly reminiscent of the animal world.

However, unlike with the Venus Flytrap, people focus simply on the movement of this plant because its movements are meek. “Shy.” It’s reminiscent of a simple animalistic trait. Although the plant cannot replicate the continual movement of animals, it folds its leaves when it’s “sleeping” (to retain water) or stressed, and theories suggest mechanoreceptors on the plant’s surface behave like nerves, sending electrochemical pulses signaling the leaves to move. In place of animal-like muscles, water-filled plant cells called collenchyma wrap around a bone-like rod called sclerenchyma (together, this structure is called a pulvinus), losing and gaining water when triggered, which raises and drops the leaves. Essentially, they have blow-up muscles filled with water.

When triggered, the plant cells chuck out their calcium ions and into temporary storage vacuoles, using osmosis to drag the water out of the area, which causes the leaf to fold.

Although not all plants move, it’s interesting to note that they use calcium for sensory input. For example, scientists have discovered that to sense gravity, amyloplasts that settle to the ground trigger calcium ions to signal shifts in gravity to all related plant cells; calcium ions also increase in locations where the plant is cut. That being said, it’s hardly ever necessary to insert calcium fertilizers into the ground because calcium is generally abundant in most soils.

The water pressure, and therefore the turgidity of the plants, returns with voltage-sensitive potassium channels.

Studies show that mimosa pudica is triggered by “all-or-nothing action potentials” like animals, and their movements can be detected on an electrocardiogram. Likewise, despite often containing alkaloids that act like anesthetics and narcotics, plants are evidenced to also react to drugs. In the case of mimosa pudica, drugged plants were vulnerable and slow to move. They have an undeniable learning memory, based on numerous studies; mimosa pudica recognizes repetitive impacts (like dropping) as non-threatening and refuses to fold, while still responding to new stimuli (like hitting).

And it’s these studies, specific to the non-threatening movements of the plant, that suddenly bring the two biological kingdoms uncomfortably closer. In myths and horror stories like the one told above, it’s the animal-like (and often human) movements of plants that make people uneasy. Moving plants contradicts the familiar, neat, and secure categorizations people make in biology.

In a way, people and plants worked together to arrive here; we only started to discover this similarity when handling a plant we had no reason to fear. Talk of this plant doesn’t dwell on the hypothetical fear that plants might one day eat people. Instead, it’s specifically on the plant’s real physical ability to move.

Even after we’ve probed this far, there’s a sick fascination with the idea that barriers to our reality, at any point, can be broken, and that the walls of our understanding are constructs. Plants can move, and people can fly. No one understands the nature of the world we live in. The closer we look, the harder it is to see it.

And, in the comfort of a mild-mannered plant like the Mimosa pudica, maybe it’s safe to explore this thought. Or maybe, this plant is flagging an existential issue that will eventually end your sanity. Although this isn’t a plant that will bite you in the ass at the next evolutionary turn, I wouldn’t pull your eyes away from it just yet.