i think there are at least three species of mimosa in singapore. the most common is the one in the first picture - the mimosa pudica. i am still not sure if the one in the second picture belongs to a different species from the pudica. the inflorescences are smaller and they are more pink than purple. the yellow mimosa is the acacia farnesiana - at least, that is my conclusion after comparing the photograph i had taken with pictures found on the internet.
there is an explanation here on why the plant closes its leaves when you touch it.
the mimosa pudica is actually a common weed found growing in open grasslands and even in some school fields. as children, we were really intrigued by it. we liked to touch it and watched its leaves closing but we would keep our distance because of the thorns found on the plant. then we would stand aside to watch, in wonder, as this sensitive plant reopened its leaves.
the yellow mimosa tends to be found at the edge of swampy areas. it seems to prefer a damp place.
