Touch-me-not

Description:

Mimosa pudica (from Latin: pudica "shy, bashful or shrinking"; also called sensitive plant, sleepy plant and the touch-me-not), is a creeping annual or perennial herb often grown for its curiosity value: the compound leaves fold inward and droop when touched or shaken, due to evolution from predators, re-opening minutes later. The species is native to South America and Central America, but is now a pantropical weed. It grows mostly in shady areas, under trees or shrubs. The stem is erect in young plants, but becomes creeping or trailing with age. It can hang very low and become floppy. The stem is slender, branching, and sparsely to densely prickly, growing to a length of 1.5 m (5 ft). The leaves of the mimosa pudica are compound leaves. The leaves are bipinnately compound, with one or two pinnae pairs, and 10–26 leaflets per pinna. The petioles are also prickly. Pedunculate (stalked) pale pink or purple flower heads arise from the leaf axils in mid summer with more and more flowers as the plant gets older. The globose to ovoid heads are 8–10 mm in diameter (excluding the stamens). On close examination, it is seen that the floret petals are red in their upper part and the filaments are pink to lavender. The fruit consists of clusters of 2–8 pods from 1–2 cm long each, these being prickly on the margins. The pods break into 2–5 segments and contain pale brown seeds some 2.5 mm long. The flowers are pollinated by the wind and insects. The seeds have hard seed coats which restrict germination.

Habitat:

Mimosa pudica is native to South America and Central America. It has been introduced to many other regions and is regarded as an invasive species in Tanzania, South Asia and South East Asia and many Pacific Islands. It is regarded as invasive in parts of Australia and is a declared weed in the Northern Territory, and Western Australia although not naturalized there. Control is recommended in Queensland. It has also been introduced to Nigeria, Seychelles, Mauritius and East Asia but is not regarded as invasive in those places. In the United States of America, it grows in Florida, Hawaii, Virginia, Maryland, Puerto Rico, Texas, and the Virgin Islands.

Notes:

The species can be a troublesome weed in tropical crops, particularly when fields are hand cultivated. Crops it tends to affect are corn, coconuts, tomatoes, cotton, coffee, bananas, soybeans, papaya, and sugar cane. Dry thickets may become a fire hazard. In some cases it has become a forage plant although the variety in Hawaii is reported to be toxic to livestock. Mimosa pudica can form root nodules that are habitable by nitrogen fixing bacteria. The bacteria are able to convert atmospheric nitrogen, which plants can not use, into a form that plants can use. This trait is common among plants in the Fabaceae family.