This is Mimosa, Mimosa pudica to be exact, a tropical shrub that closes its leaves when touched. Also called Sensitive Plant, Sleepy Plant, Action Plant, or Shame Plant, and one I particularly like – the Tickle-Me-Plant. It’s a creeping flowering plant of the pea family Fabaceae and is often grown for its curiosity value - the sensitive leaves fold inward and droop when touched or shaken and re-open a few minutes later. The Latin word ‘pudica’ means ‘bashful’ or ‘shrinking’, because of its reaction to contact.

Sleepy Leaves

Quite a number of other plant species have foliage that undergo changes in leaf orientation, termed ‘sleep’ or ‘nyctinasty’ movement. Mainly we see flowers that close – daisies do it, as do tulips, morning glory and hibiscus, and these are mostly light-sensitive reactions. The Mimosa pudica weirdly closes its leaves when touched, and this is probably a ploy to trick insects into thinking the plant is dead and therefore not good to eat, or a defence against those who might be startled by the movement and fly off. Clever. The plant's quick response to touch is due to rapid water release from specialised cells located at the bases of leaflets and leaf stalks. The leaves re-open a few minutes later on their own accord.

The plant comes from Central and South America and features delicate, fern-like leaves with delicate light purple pom-pom-shaped flowers, and is a popular houseplant due to its relatively easy care.

It usually only grows 15-50 cm tall but can reach up to 1 m or more in height when supported by other vegetation. Mimosa pudica is not the only plant to move in response to stimuli - some close up their leaves a few hours before dusk, and then re-open them a few hours before dawn. It is thought that these 'sleep movements' aid water conservation as well as defence against being eaten.

Is it Bad to Touch a Touch-Me-Not Plant?

Although one of its common names is the Touch-Me-Not Plant, Mimosa pudica is not harmed when touched, and it will not harm you either – it has earned its various nicknames because of its rapid response to touch. Mimosa pudica is a fun plant to have around the home and makes an interesting conversation piece.

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Let There Be Light

This sensitive plant needs bright light up to eight hours a day, and can even tolerate some direct sunlight. If it doesn't get enough sunlight, the leaves may close up and won't produce blooms. As a houseplant, an east-facing window is ideal. However, if you lack the proper light, you can supplement with a full-spectrum fluorescent grow light. Outdoors, you can plant Mimosa pudica in full sun or partial shade, as long as it gets its full sun requirement.

Sensitive Plant Care

They say caring for the captivating Mimosa pudica isn't difficult once you understand what it needs, and it requires the same care and attention whether indoors or outside. It likes consistently moist soil but not wet, as this can lead to root rot. Plant it in a pot with drainage, and water it when the top of the soil begins to dry out. If it is planted in the ground, make sure you modify the soil to improve drainage before planting and water it when the top inch or so begins to dry.

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Mimosa hostilis v Mimosa pudica

Another variety of Mimosa is totally different and shouldn’t be confused with our touch-sensitive pudica. Mimosa hostilis does not show movement upon touch and is more of a perennial tree or shrub, that can grow to 4–5 m tall, with white, fragrant flowers that occur in loosely cylindrical spikes.

Another famous plant that is sensitive to touch is the Venus Fly Trap, which like other carnivorous plants attracts, traps and digests flies, ants, spiders, etc for the nutrients they contain. This plant is best known for its ‘trap’ made of two hinged lobes at the end of each leaf. If you happen to stimulate those trigger hairs with your finger, then the trap will start to close, but will probably damage the plant more than it will damage you!

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan