Mimosa is from the Greek mimikos and Latin mimus meaning 'to mimic' and osa meaning 'many' and refers to the many flowers that combine to give the appearance of a single flower.
Pudica is the Latin word meaning 'bashful' or 'modest' and refers to the way the leaves fold up when touched.
Common Sensitive plant - because the leaves fold up when touched.
Summary:
A sprawling, many branched, purple ball flowered plant with paired leaflets that fold up when touched and at night.
Description:
Cotyledons:
Two.
First leaves:
First leaf is only divided once, not twice, like later leaves.
Leaves:
Alternate. Leaves fold flat against the branches when touched and at night.
Petiole - Long.
Blade - Dark green, divided twice. One or two pairs of opposite primary leaflets divided into 12-25 pairs of opposite secondary leaflets that are oblong or parallel sided with pointed tips and 9-12 mm long by 1.5 mm wide.
Stems:
Sprawling, red-brown to purple, stiff, rounded, 300-1500 mm long. Branching profusely. Scattered thorns.
Flower head:
Globular or egg shaped. several flowered, 9 mm diameter. On prickly 12-25 mm stalks arising from the upper leaf axils.
Flowers:
Purple-pink. Tubular.
Ovary -
Sepals -
Petals - 4. Joined.
Stamens - 4, purple-pink.
Anthers -
Fruit:
Oblong, flattened, 1-5 seeded, 10-20 mm long by 3-6 mm wide. Pointed at the tip. Prickly edge. In clusters in leaf axils. Breaks into one seeded segments when mature.
Seeds:
Light brown. Flattened. Fine granular surface. 2.5-3 mm long.
Roots:
Taproot to 1000 mm deep. Slightly woody. Nitrogen fixing nodules on feeder roots.
Key Characters:
Biology:
Life cycle:
Seed germinates at any time of the year with a flush in the wet season from November to March. It grows quickly and the stem branches many times as it grows. Flowering starts 3 months after germination and is continuous on warm moist sites.
Physiology:
Shade tolerant.
Reproduction:
By seed.
Flowering times:
Most of the year.
Seed Biology and Germination:
Seed may remain dormant in the soil for many years. Seed has survived 19 years of dry storage at room temperature.
80% of freshly harvested seed will germinate under alternating temperatures of 30/20oC. Remaining hard seed needs acid or physical scarification before it will germinate.
Vegetative Propagules:
None.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Stiff bristles on the pod attach to animals, wool and clothing for transport.
The one seeded segments move freely in water.
Sand and gravel used for roads and buildings is another source of spread because seed may be dormant in the soil for many years.
Each plant produces 600-700 seeds in a year.
Origin and History:
South America.
Probably introduced as an ornamental garden plant.
Distribution:
NSW, NT, QLD.
Habitats:
Climate:
Sub-humid to humid, sub-tropical and tropical regions.
It is an aggressive weed in the very high rainfall areas
Soil:
On a wide range of soil types.
Plant Associations:
Significance:
Beneficial:
Fodder.
Because of its shade tolerance it is a useful pasture plant in coconut plantations.
Used as a competitor for Blady grass control in China.
Detrimental:
Weed of cultivated areas, roadsides, gardens and disturbed habitats and crops such as maize, sugar cane, rubber, tea, sorghum, soybeans and rice, or tropical pastures.
Toxicity:
It is suspected of poisoning cattle. Sheep appear to break the toxin down in their rumen.
Symptoms:
Loss of hair and wool.
Treatment:
Legislation:
Noxious weed of NT and WA.
Management and Control:
In arable land, cultivation normally keeps it under control. In pasture areas, triclopyr, dicamba, picloram and glyphosate have been used for control.
Thresholds:
Eradication strategies:
Herbicide resistance:
Biological Control:
A biological control program is in progress.
Related plants:
Giant Sensitive plant (M. invisa)
Giant Sensitive tree (M. pigra)
Plants of similar appearance:
References:
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #823.3.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P447-449. Photos.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.