The mimosa plant belongs to the pea family (Fabaceae). The word mimosa comes from the Greek word mimos or “mimic,” referring to the moving leaves that mimic animal’s sensitivity. The Mimosa pudica, also known as “sleeping grass,” or “sensitive plant,” is one of the more prominent species. The word pudica means “shy.” Globular lilac pink flowers and leaflets suddenly droop when touched.
Most species of mimosa thrive as herbs or undershrubs. An example of one of the few tree species is mimosa Albizia julibrissin, also known as silk tree or silky acacia, a medium-sized tree that reaches up to 20 to 40 feet.
Native to Brazil, the sensitive plant arrived in the tropics, and caused a noxious weed invasion in the Caribbean, South America, Hawaii and Puerto Rico. This plant can compete with native plants in open areas or forest edges.
In young plants, the Mimosa pudica has erect stems that transform to 5-foot long creeping or trailing stems. Pale, lilac pink flowers in summer look like fluffy balls, yet each cluster holds individual flowers. Leaves of most species are bipinnate, where leaflets give rise to other leaflets. The sensitive plant folds its foliage at dark and reopens in light. Fruit consists of two to eight pods. Each pod holds brown seeds. Certain species have poisonous roots.
The sensitive plant can thrive in one of two types of life cycles: as an indoor annual ornamental with showy flowers; as an outdoor perennial plant in the tropics. Habitat includes moist, waste ground, open plantations, and well-drained soils with open sun. The Mimosa pudica can exist as a dense ground cover, with thorny stems that make grazing difficult and prevent reproduction of other species. The sensitive plant is drought and frost tender, and sensitive to over-watering. On dry, wild lands, this plant poses a fire hazard.
Although the Mimosa pudica acts as a weed in some regions, certain tropical countries benefit from the sensitive plant as a cover crop with nitrogen-fixing properties. The sensitive plant contains bacteria that can convert atmospheric nitrogen into a usable form for plants in poor soil.
Threats to the Mimosa
A fungus causes mimosa vascular wilt, the most devastating disease of the mimosa tree. Distribution of mimosa vascular wilt ranges from Maryland to Florida and west to Texas. Symptoms appear in branches that turn yellow, dry and wilt. Affected branches later turn brown and fall. The outer ring or sapwood usually discolors. Symptoms progress to the plant’s death.
A fungus distributed by the soil, Fusarium oxysporum, enters through the plant roots, and blocks the vascular or water conducting system. This fungal pathogen prevents the transportation of vital water and nutrients to the leaves. Wilting and death can result.
Mimosa vascular wilt disperses by wind, water, animal actions, birds and human activities. Disease spreads from infected trees to healthy trees. With no known cure for mimosa vascular wilt, avoid spreading the fungus, such as by moving the soil. If the mimosa is in tree form, remove and destroy the trees by burning.