Sensitive Plant (Mimosa pudica) Plant Profile

by | Botany

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In this plant profile from HerbSpeak, you’ll learn about the fascinating sensitive plant – the one and only Mimosa pudica.

I’ve recently come into possession of one of these myself, after several years of being fairly lowkey obsessed with the idea that a plant can not only respond directly to touch without carnivorous habits, but it can also learn what sensations aren’t going to hurt them, over time.

But, I might be getting a bit ahead of myself; for now, let’s dive into the basic description of this plant.

Mimosa pudica – Description

Mimosa pudica is an annual tropical plant native to South America, but has been established and thrives in many countries, of which it is most often considered invasive. It is most often grown as an ornamental, as it is a fast-growing leafy shrub.

This plant thrives in a wide range of disrupted soils. Most notably, it tends to show up in mining sites, along railways, near volcanoes, or in other areas where the soil has been thoroughly disturbed.

Meadows, coastal areas, and grassland are all hospitable areas for the Mimosa, where the soil stays moist and warm. The poorer the soil, the more vigorous the plant works to compete with local native flora, though it can establish itself in just about any type of soil.

As a creeping shrub, the plant has stems with multiple leaflets attached at the petiole. It is well-known for its globular pink flowers with strand-like petals that are thin and end in small white or yellow heads.

This puffball-type flower is lighter in color and often smaller and rounder than the more popular Powder Puff tree, Calliandra spp. or the Silk tree, Albizia spp. which are both trees with similar leaflets that remain in place when touched.

Mimosa pudica Common Names

This plant comes with many different common names like the shy plant, the tickle me plant, or the sensitive fern, due to its natural tendency to “shy away from” touch.

Other common names play on this theme as well, such as the touch-me-not plant, the shame plant, or humble plant. Quite a few plants bear the name touch-me-not, however, so this name isn’t in as common usage as others.

Since the plant is either established or invasive outside of its native zone, it tends to gather a lot of informal common names as well, so each region may have various names associated with it as well.

Noteworthy Characteristics

As a fast-growing creeping vine or shrub, the Mimosa pudica has medium-sized, pink globular flowers. It is generally considered an annual groundcover, forming a dense net of leaves that keeps other plant species from reproducing.

It is most often cultivated for its fast rate of growth, bright flowers, and most notably for the novelty of a plant that moves rapidly.

When touched, individual stems will close its leaflets for several minutes until it slowly unfolds again. Likewise, when the stem is touched, the whole stem will bow in response, slowly regaining its original turgidity over a few minutes.

The plant responds this way to both touch and other disturbances like shaking.

Despite its ability to move rapidly, the Mimosa is not carnivorous at all. It is thought that the rapid movement is a defensive mechanism against herbivorous animals and insects, and that the movement might deter them from eating the leaves.

Rapid Plant Movement

This plant has often been studied, alongside the Venus flytrap to better understand the mechanisms behind rapid plant movement.

Its unique ability to close leaflets with the sensation of touch relies on a sensory area within the plant called the pulvinus, which reacts rapidly to movement. While all plants move to some degree – some even in response to touch such as in the case of tendril or vining plants – Mimosa pudica is one of the few that respond to touch with rapid plant movement. (1)

“[…] electrical signals, in particular action potentials, are likely to be important for the rapid movement and long-distance signaling in M. pudica. While a large part of the underlying mechanisms is yet to be determined, the contribution of several ions and cytoskeleton playing a role in these events has been suggested.”

Department of Biochemistry and Molecular Biology, Saitama University

Scientists are still learning exactly why, how, and to what extent the mimosa plant can move, but it is clear that the pulvini – of which there are three primary areas that affect rapid plant movement – are responsible for this motion.

To equate it to a human example, it seems to act similar to the abdominal muscles when bending or rotating the torso. While the external obliques might be fully engaged, the internal obliques help stabilize the body.

Likewise, when turning to the right, the muscles on the right stabilize the body, but it is mostly the left side engaged.

In Mimosa, the pulvini seem to have a similar response; the primary and tertiary pulvini are the most sensitive to external stimulus, and both are essential to the plant’s movement.

Habitual Learning

Almost all organisms can “learn” or acquire information about the environment and then modify their behavior in response. It is no secret that plants an animals alike can store memories, but can plants learn in the same way?

Because rapid plant movement is such an unknown phenomenon to botanists, it leaves us open to exploring these possibilities with real-time data.

 

Unfortunately, many of the studies that happened on the movement and learning of Mimosa pudica occurred earlier in the century, between the 1950s and 1980s by psychologists which leaves a lot of the testing and results data as doubtful at best, and at worst, lost to time.

These psychologists were interested if plants reacted similarly to animals, and unfortunately, the cross-disciplinary interest waned over the years.

While the interspecies communication via rapid plant movement seen in the video is quite cool, the research on learning behavior of plants capable of rapid movement has come back in small, under-funded waves. Little additional research has been done to shed light on habituation and learning potential of plants.

It has long since been established that plant can learn and adapt to the environment in response to trauma.

In the case of shrubs and trees, removing the apical bud causes future growth to be symmetrical. However, simply wounding one side of the premature bud’s cotyledon will cause it to grow asymmetrically, favoring the healthier side even after the initial wound had healed.

With repeated exposure, plants may even undergo a change in the plant’s molecular structure which changes gene expression. This leads to future generations of plants learning from the parents’ experiences.

What a superpower that must be indeed.

Habitual learning, however, is a topic of some contention over whether the plant has learned on some pseudo-cognitive level. In this type of learning, Mimosa pudica is a popular test subject. (2)

Biologist Monica Gagliano designed an experiment in 2013 which attached several mimosa plants to a controlled drop machine.

It was found that the leaf-folding response can be achieved with a drop from 15 cm, and the leaves were measured with calipers at both full openness as well as full closure.  

“Astonishingly, Mimosa can display the learned response even when left undisturbed in a more favourable environment for a month.”

Monica Gagliano

This test continued, dropping the plants in quick succession another 60 times, seven days in a row. By the end of the drop training, the leaves were fully open, but also failed to respond to the drop stimulus in any measurable way.

To rule out leaf exhaustion or another factor, the plants were then given a novel experience: they were attached to a shaker plate and shaken. The stimulus, not unlike the stimulus of the drop, would not be something the plant is accustomed to.

Despite being habituated to the fall, the plants quickly responded to the shaking stimulation by closing the leaflets.

Gagliano’s work has caught onto the mainstream press and since Nat Geo covered the experiment in a 2015 article, it hasn’t seemed to leave the public’s eye since, with headlines promising grandeur of plant learning and the miracle of plant intelligence, which is a quite stretch from the original experiment.  

Is it Bad to Touch Mimosa pudica?

While this shy plant does collapse into itself when touched, is there a chance that touching it is harmful to the plant?

Well, there is no clear answer.

There is no indication that touching it occasionally harms the plant. After all, the adaptation is there as a defensive mechanism to grazing or insects in the wild.

The mechanism behind its droopiness or leaflet closure is due to a drop in water pressure, which is not inherently bad for the plant.

Plants that are over-stimulated, shaken too much, or endure too much physical stress in general can become stressed, however, and there’s no reason to believe that Mimosa pudica is any different in this regard.

How to Identify Mimosa pudica from Other Species

While there are many trees, shrubs, and vines with a similar leaflet structure as Mimosa pudica, it can be difficult to identify at a glance.

Most identification between different species comes down to response to touch, the type of flower, number of leaflets on a stem, and the stem shape and presence of cilia along the plant.

While the response to touch may be the most obvious indicator of whether the species is M. pudica or another altogether, comparing the stems, leaflet shape and flowers help to identify it over other leaflet-bearing plants.

Mimosa pudica typically has cylindrical stems with 12-25 pairs of leaflets along a stem with visible bristly pulvini along the stem.

Is Mimosa pudica the Only Species that Moves?

Mimosa pudica is the only plant species in the pea or legume family that has the characteristics of rapid plant movement. This response to touch is called thigmonasty, which is the response to touch or vibrations. Unlike tropisms, this nastic movement is not dependent on the direction of the stimulus.

It is, however, not the only plant in the family that responds to touch. Most plants respond to touch in a much slower way.

Peas and legumes themselves are famous for curling around whatever it can grab onto, seeking out new structures to support its fast-growing tendrils.

This is generally considered to be a form of thigmotropism, which is the directional response to a touch stimulus, altering how the plant grows. This response comes in many forms and can even be responsible for directional root growth towards underground sources of water.

Is Mimosa Flower Poisonous?

No, the flower is not considered poisonous to humans. According to PFAF, the flowers are considered edible, and seeds are sometimes pressed for their oil. Some extracts from the flower and seed are available in the market as a supplement.

Other sources note that consuming the seedpod, or oil from the seeds can be detrimental to the absorption of certain B vitamins, resulting in ill side effects. It should also be noted that in large doses the roots may be toxic.

As the plant grows, the hairs along the stem can harden, causing gastrointestinal distress in grazing animals, making it necessary to graze in the earlier stages of growth.

Are Mimosa Pudica Easy to Care For?

Yes, Mimosa pudica plants are easy to care for as a container houseplant. They thrive in the same well-lit, moist conditions that most humidity-loving plants do, making them an easy addition to any tropical houseplant keeper’s collection.

The delicate foliage blooms with beautiful pink puffballs from mid-summer to fall once it is large enough, making it a stunning plant that even amateur houseplant keepers can enjoy.

Uses of Mimosa pudica

Mimosa pudica is a fascinating plant, so it’s no wonder that scientists and herbalists alike find many uses for it. Most popularly in the western world, the plant is studied for its ability to quickly react to touch, giving us a better understanding of plant behavior.

In regions where it is native, it has been used as a medicinal plant, and as a member of the legume family, it has nitrogen fixing properties which makes it beneficial for placing near certain crops.

Botanical Research

Since the plant has been discovered, scientists have been enthralled by the plant’s ability to respond to touch, and even more bewilderingly – learn from its experiences. (3)

Mimosa pudica teaches us a vital lesson about the nature of learning and intelligence. [Mimosa] shows that we share the faculties and processes once considered exclusively human not only with other animals but also with plants.”

Botany.one

Now, there is a lot of debate around the subject as scientists are determined not to put plants into such anthropomorphic terms. Still, there is an evolutionary advantage to the plant ‘learning’ from its experiences.

To put it more scientifically, the plant becomes habituated to certain experiences, and may cease to respond once it determines the stimulus is repetitive yet not harmful.

Nitrogen Fixation

All members of the legume family (Fabaceae) are famous for their nitrogen fixation properties, which includes the Mimosa pudica plant. These plants form a symbiotic relationship with certain bacteria in the soil. These bacteria work to take nitrogen from the air and exchange it into a form of nitrogen that the plant can use within the soil.

The plant receives usable nitrogen in nitrogen-poor soils, while in return, the bacteria receive benefits from the plant such as water or other nutrients that are essential to their growth.

Medicinal Applications

Mimosa pudica is a traditional herbal that has been used for centuries in the treatment of several ailments. The roots have been used to treat diarrhea, fever, ulcers, asthma and snake bites.

The leaves are often ground into a paste to treat pink eye, infections of the feet and toes, insomnia, and sometimes even depression. The seeds have been used in treating urinary problems.

This is not to say that Mimosa pudica is without its side effects; temporary fertility issues are a common problem associated with this plant.

Caring for the Sensitive Plant

Enthralled by the mysticism of this plant, many gardeners and houseplant growers want to add Mimosa pudica to their collection.

Caring for the plant is relatively easy and the tree can be kept either in a little pot on your desk, or be allowed to grow to it’s fullest potential in the garden or in larger pots.  

Temperature

Native to tropical climates, the temperature of M. pudica reflects its typical environment as an understory tree. Thriving in high humidity, anywhere between 60-85 degrees Fahrenheit (16-30 Celsius) is acceptable for this tree.

How Often Should I Water Mimosa Pudica?  

You should water M. pudica lightly and frequently. The goal is to keep the plant’s soil moist without compacting it or letting water sit in the soil, which can contribute to root rot.

Water-logged soil will quickly become the death of Mimosa pudica, which is problematic for beginning houseplant lovers who don’t understand the balance of letting a plant thrive without smothering it. It’s easy for even experienced houseplant growers to find themselves tending to the plant more than they should with how fascinating it is.

Furthermore, without the right type of soil, it can be difficult to balance your watering routine with the amount of humidity M. pudica needs. Dry soil is just as bad as water-logged soil, causing the plant to wilt and crisp up as it doesn’t have enough water to reach the leaves and allow it to transpire and photosynthesize.

Soil

M. pudica thrives in well-draining, loamy soil. While not surprising given that this is the main soil type that tropical plants tend to thrive in, it’s an especially important factor for M. pudica to grow to its fullest potential in just a single year. Keeping the soil moist and well-draining with beneficial bacteria and mycorrhizae will speed along the tree’s growth significantly.

Propagation

M. pudica is famous for easy propagation as the roots are invasive and will sprout additional trees if left unchecked. For this reason, it should never be grown as a garden plant in areas where it is not native.

Besides runner roots, you can propagate Mimosa pudica by taking cuttings of individual branches. These branches and stems should have at least one node with leaves 1-2 inches above the clean cut.

Keep the propagated node moist by packing it in with peat moss or a sustainable alternative. The air around the new plant should remain humid, so you may need to create a dome around the seedling. Allow the dome to breathe a few minutes a day between spritzing for an exchange of oxygen.

Pruning

Pruning is not necessary, but in lower-light conditions it may begin to get ‘leggy’ or look sparse in leaf growth. To keep M. pudica looking full and bright, you should provide adequate, even light for the plant, and begin to prune back any stems that grow exceptionally long between nodes. Only prune two or three leggy stems at a time, as the plant will need to recuperate its lost energy.

How Quickly Does Mimosa Grow?  

Mimosa pudica can grow unfathomably quick compared to other plants, another trait that seems to be shared by the legume family. In the right conditions, the growth rate of M. pudica can exceed 5 feet in the first year of growth.

The plant, however, is highly sensitive to its environmental conditions, so it is unlikely for it to reach this height unless you live in a tropical or sub-tropical environment. Humidity, soil, light, and temperature are all important factors in determining its growth rate.

How Long Do Mimosa Flowers Last?

Flowers will last for a few weeks on average in the best conditions. Typically, a tree will only have one bloom at most in captivity but may not bloom at all in container conditions because of its average lifespan.

Houseplant growers lucky enough to achieve blooming status should enjoy the bright pink puffballs to their fullest, as the results are quick to disappear.

Gardening Problems with Mimosa

Unfortunately, in areas that gardening is possible with Mimosa pudica, problems arise. You may experience some of these issues with container plants as well, though it is not common for container plants of Mimosa pudica to get as large because of the conditions they are first grown in.

Root Rot

Root rot is problematic with M. pudica because the roots need well-draining, loose loamy soil to allow for oxygen exchange in the roots. Without this ability, the plant cannot uptake water, and the roots will rot as they are unable to move away from standing water within the soil.

Red Spider Mites and Mealybugs

Many houseplant growers claim that Mimosa pudica is disease resistant, and while this is true for many common diseases, it isn’t immune to everything. Common houseplant pests like red spider mites or mealybugs can be problematic.

This plant is best quarantined if you have an infestation and carefully monitored. Spritzing the plant with water, however, is an easy solution to getting rid of these pests in a way that doesn’t damage the foliage.

Why Is My Mimosa Pudica Turning Yellow?

Mimosa pudica is a sensitive plant indeed – it requires humidity to thrive. If the leaves are turning yellow, it might be a sign that it isn’t getting enough humidity for what it needs.

Like many other tropical house plants, 55% relative humidity is critical to keeping the plant healthy and thriving, as the leaves can transpire adequately in this range.

If you don’t have enough humidity in the area, you might notice the leaves fail to respond to touch as quickly. This can also happen if the plant is thirsty.  

Ecologically Invasive Roots

The roots of Mimosa pudica are fast-growing and invasive. As a part of the legume family, the growth rate is exceptionally fast when the plant is given conditions it thrives in.

Unfortunately, for most individuals looking to grow the plant, it is more of a novelty than anything else, meaning it is not native to the area it is being planted. Because of how fast the roots grow, causing the tree to propagate over several years, it’s important to keep this plant as a houseplant only.

Even in areas where the plant can survive, such as areas in the southern United States, it should not be planted because of how ecologically invasive the roots are. The plant is native to the tropics of southern Mexico to South America, as well as the Caribbean.  

Why is My Mimosa Tree Not Blooming?

You may have gotten the plant at a nursery that advertised its beautiful pink blooms, and you’re waiting for your pinky-sized plant to produce miniature puffs of cotton candy-colored balls.

Unfortunately, it takes a while for the Mimosa plant to bloom. Most trees will not bloom until they are 10 feet or taller with plenty of branches for the blooms to develop on. This means that most houseplant lovers won’t be able to see their Mimosa plant bloom unless they provide it with adequate care and dedication.

References
  1. Takuma Hagihara, Masatsugu Toyota, Mechanical Signaling in the Sensitive Plant Mimosa pudica L., https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284940/
  2. Monica Gagliano, Experience teaches plants to learn faster and forget slower in environments where it matters, https://pubmed.ncbi.nlm.nih.gov/24390479/
  3. Monica Gagliano, What a Plant Learns. The Curious Case of Mimosa pudica, https://botany.one/2019/08/what-a-plant-learns-the-curious-case-of-mimosa-pudica/

 

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About Destynnie K. Berard
I am a lifelong naturalist who believes a good sense of humor is essential to staying happy. ★ After traveling for years, I settled in New England, falling in love with the diverse landscape the Northeast has to offer, and began pursuing conservation in earnest. ★ My career background is in enterprise marketing and communications, which provides me with a unique perspective of ecological relationships.

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