Native to the tropics of Central and South America, Mimosa pudica is a creeping shrub or short-lived perennial that is commonly called "sensitive plant" for an intriguing leaf movement that occurs when it is touched. The leaves of a sensitive plant are lined with tiny hairs that are highly responsive to touch, temperature, and motion, folding inwards when triggered. The plant also closes its leaves at night. This response to various forms of stimulation is a part of this plant’s natural defense mechanism. Sensitive plant has delicate, fern-like leaves and light purple flowers that resemble small pom-poms. Young plants grow upwards but quickly develop an outward creeping habit. Although sensitive plant is hardy in zones 7 to 13 and is sometimes grown outdoors in those regions, it is more often grown as an excellent low-maintenance houseplant. It should be grown cautiously outdoors, as it can escape and naturalize easily, as it has in some southern U.S. states.
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Sensitive plants may be sold as potted nursery starts, but it is more common to plant them from seeds started in the spring. They have a very fast growth rate, and in the garden, they have been known to reach a full 5 feet in width in their first growing season. They are very short-lived, however, and decline with every passing year, so they are often planted afresh each year as annuals.
|Common Name||Sensitive plant, touch-me-not, sleepy plant|
|Botanical Name||Mimosa pudica|
|Plant Type||Shrub, herbaceous, perennial, annual|
|Mature Size||18 in. tall, 1-5 ft. wide|
|Sun Exposure||Full, partial|
|Soil Type||Well-draining, loamy|
|Soil pH||Acidic, neutral|
|Flower Color||Purple, pink|
|Hardiness Zones||7–13 (USDA)|
|Native Area||Central America, South America|
Sensitive Plant Care
Sensitive plant (Mimosa pudica) is an easy-to-care-for flowering plant in the legume family Fabaceae. With plenty of light and lots of water, even an amateur houseplant hobbyist can enjoy the delicate foliage and unique movement of sensitive plant in the home. Unlike the venus fly trap, the sensitive plant closes its leaves purely in self-defense; it is not carnivorous.
As a landscape plant, sensitive plant is most often used as a sunny ground cover, but one that must be watched to prevent rampant spread. Individual plants are short-lived, but they easily self-seed and volunteers may achieve full size in a single season.
As houseplants, sensitive plant quickly declines after it flowers, so it, too, is often grown as an annual, planted afresh from seed each year. Potted plants become less attractive after two years or so.
Mimosa pudica is invasive in tropical climates. Use caution when planting outdoors as it can spread quickly and naturalize readily. Each plant can produce as many as 700 seeds each year. The seed pods have clinging burrs, which allow the seeds to travel long distances.
Sensitive plants are not very shade-tolerant. They thrive with eight hours of daylight and can tolerate partial shade, but languish badly in full shade. When growing them indoors, the ideal location is directly in front of or beside a bright sunny window. If the leaflets remain closed during the day, it indicates that the plant is not receiving enough light.
Well-draining, loamy soil is ideal for a sensitive plant growing in the landscape; its roots cannot survive in severely compacted soil. Enhance the soil with peat moss to improve drainage. In its natural environment, the sensitive plant lives in soils that are low in nutrients. Therefore, it does not require overly rich soil or frequent fertilizing.
When grown as a houseplant, a standard commercial potting mix is a good growing medium.
Keep the soil consistently moist for a sensitive plant but not waterlogged. The sensitive plant cannot handle wet feet and will develop root rot if left sitting in excess water. As a general principle, water a sensitive plant once the top of the soil begins to dry out. Water sensitive plant a little more sparingly in the winter.
Temperature and Humidity
Sensitive plant can be grown as a short-lived outdoor perennial or shrubby ground cover in zones 7 to 13, but it is most often grown indoors as a potted houseplant. Potted specimens thrive in typical indoor temperatures of 65 to 75 degrees. The sensitive plant enjoys moderate to high humidity. Unless your house is particularly dry, the average household humidity should be sufficient for a sensitive plant. In regions where winter air is especially dry, run a humidifier close by or place the sensitive plant pot on top of a tray of pebbles filled with water to increase humidity.
If grown as potted patio plants, sensitive plants will perform best if moved indoors when temperatures stray outside the 65 to 75 degree ideal range.
Sensitive plants occur naturally in nutrient-poor soil, so fertilization is generally not required. However, if desired, you can give the plant an extra boost during the growing season by applying a high-potassium liquid fertilizer diluted to half strength every few weeks. Always ensure that you water a sensitive plant before fertilizing it to avoid burning the delicate roots.
Types of Sensitive Plant
There are no named cultivars of sensitive plant commonly available. Where it is grown at all, it is the species form that is cultivated.
Another plant in the genus, Mimosa tenuiflorae or M. hostilis (Mimosa tree) is a small landscape tree that can be grown in zones 9 to 12. In Central and South America, it is sometimes used by indigenous cultures to make psychoactive concoctions for ritual use.
Prune a sensitive plant regularly to keep it full and bushy rather than leggy. You can prune a sensitive plant any time of the year. Since Mimosa pudica is a creeping plant, trim off trailing stems or train them to climb a trellis to keep the plant looking nice.
Propagating Sensitive Plant
Propagation of these plants is usually done by seed (see below), but it can also be done by stem cuttings. Here's how to do it:
- First, cut a 4- to 6-inch stem tip that contains at least one exposed leaf node.
- Plant the cutting in a small pot filled with a mixture of peat moss and perlite.
- Place the pot in a warm, bright spot, and cover it with clear plastic. In one to four weeks, the cutting will root and can be planted in a larger pot or in the garden.
How to Grow Sensitive Plant From Seed
Propagating sensitive plants by seed is the most reliable way to grow new plants. However, the seeds need a little encouragement to germinate. Follow these simple steps:
- Order seeds from a reputable source, or collect seeds from the dried seed pods left behind after the summer flowers have faded.
- In spring, prepare the seeds by scarifying—scratch the tough exterior with a sharp knife or soak them in water overnight.
- Sow the seeds in small pots filled with moistened potting mix. Cover them with a small amount of additional potting mix.
- Set the pot in a bright warm location. Germination usually takes only about one week.
- Pot up into larger containers as the roots fill the pot and become visible through the drainage holes in the pot.
Potting and Repotting Sensitive Plant
Sensitive plants grow fast and require multiple repottings if they outgrow their pot. When you notice the roots poking out of the drainage holes, it’s time to transplant the plant—you may need to do this several times in a single year. It's natural to see leaves drooping after repotting; give it some time—the plant will bounce back. If, after blooming, the plant deteriorates to a point where it is unattractive, save the seeds, discard the plant, and plant it again. Many growers plant new seeds each year, discarding the old plants after they flower.
Sensitive plants are considered perennial, but indoors, they deteriorate after blooming. The best strategy is often to grow sensitive plants as annuals, discarding them after you save their dried seeds in order to propagate new plants.
Watering should be slightly reduced for the winter months—both for indoor houseplants and garden plants that go into semi-dormancy for the winter.
Several pests are common to sensitive plants. These include spider mites and mimosa webworms, both of which wrap the leaves of the sensitive plant in webs that hinder their responsive closing. Sensitive plants are also susceptible to other common houseplant pests such as mealybugs and thrips. Spraying with a non-toxic horticultural oil is an effective treatment for these common houseplant pests.
Fortunately, sensitive plants are not especially prone to any diseases.
How to Get Sensitive Plant to Bloom
Sensitive plant is usually grown for its delicate foliage that reacts in such a unique fashion to physical touch and other stimuli, so the short-lived pink-purple pom-pom flowers that sometimes appear through the summer are a pure bonus. When these blooms do not appear, it is usually because the plant is not getting enough light, which is a common issue with indoor houseplants. Try moving your plant to a sunny outdoor location for the spring and early summer months, or supplement your indoor plants with artificial light, which may stimulate more flowers.
Lack of flowers can also be caused by temperature extremes. Try to keep the plant in the ideal 65 to 75 degree range. Plants that spend time in extreme temperatures will often refuse to flower.
Common Problems With Sensitive Plant
First-time growers using sensitive plant as an indoor houseplant are sometimes surprised by how fast the plant declines. Most common houseplants are tropical evergreen perennials that can live for many years if cared for properly, but sensitive plant is not such a species—it will begin to decline immediately after it flowers for the first time. Efforts to prolong its life usually have little effect. Instead, it's best to simply save some seeds from the plant, plant a new specimen, and discard the parent plant after its appearance begins to decline.
These plants are also prone to developing leggy stems without much foliage—this is usually a response to inadequate sunlight. Make sure the plant gets at least 8 hours of daylight—supplemented with artificial light if necessary—and prune back the stems frequently to keep the plant bushy and full.
How exactly does this plant close its leaves in response to touch?
The structure of the leaves in sensitive plant have a hinge-like mechanism containing motor cells that work in opposite actions. The plants react to stimulus by releasing chemicals that cause water to flow out of the motor cells on one side and into matching cells on the other side. This flow creates a pressure that causes those cells to collapse or expand, making the leaflet squeeze shut. Left undisturbed the leaflet slowly opens again after a few minutes.
If this plant is so short-lived, how can it be so invasive?
Sensitive plant doesn't expand through rhizomes, but while individual plants don't live very long, each can produce as many as 700 seeds that are easily transported by clinging seed pods or by distribution on the wind. Some of these seeds germinate and sprout very quickly, but others may remain in the soil for months or even years until the hard coatings break down and allow the seed to germinate. Thus, it's possible for new plants to spring up miles away from the parent plant, years after the parent plant has naturally died off.
Is there any benefit to sensitive plant in the landscape?
Although it is usually regarded as a weed when it escapes garden cultivation, sensitive plant is known to increase nitrogen and potassium in the soil—much the way that other members of the legume family do. And some studies show that some sensitive plant species can remove arsenic and heavy metals from contaminated soils.
Mimosa pudica (sensitive plant). CAB International.
Tepezcohuite. The University of Texas at El Paso.
Light, Temperature and Humidity. Texas A&M Agrilife Extension.
Pérez-Hernández, Valentín, et al. The Potential of Mimosa Pigra to Restore Contaminated Soil with Anthracene and Phenanthrene. REVISTA TERRA LATINOAMERICANA, vol. 38, no. 4, 2020, pp. 755–69. doi:10.28940/terra.v38i4.603