Touch Me Not

*Mimosa pudica*

How to know it

A low sprawling weed with small feathery leaves made of many tiny leaflets, and round pink pompom flowers. Grows wild on waste ground, verges and lawn edges throughout the tropics. Thin stems carry small thorns.

What it does

The leaves fold inward within a second of being touched, then reopen after a few minutes. The movement is caused by water moving out of cells at the base of each leaflet. It is thought to deter grazing animals and insects.

Safety

The stems carry small sharp thorns, so show children to touch the leaves and not to grab the stem. Otherwise harmless.

Two things to do with children

Let a child touch one leaflet and watch. Then let them wait for it to reopen, which takes longer than they expect and is a lesson in patience by itself.

Time how long it takes to reopen, in the sun and then in the shade. The difference is measurable and it turns a novelty into an experiment.

Worth knowing

You almost certainly already have this growing somewhere on your site. Look along path edges and in patchy grass before you go looking for a nursery.