The below description is taken from LEGO.com.
“Om nom nom nom.”
Have you ever met a semi-intelligent ambulatory plant? One very alarmed Minifigure recently has! The Plant Monster used to be the Monster Scientist’s houseplant until the silly mad doctor accidentally gave it too much of his experimental super-growth fertilizer, causing the horticultural horror to sprout arms, legs, spiky vines, and one huge appetite.
Lurking in gardens, bushes, and anywhere else that’s green, the Plant Monster bides its time and then springs out to swallow up passers-by with a gulp and a happy smack of its leafy flytrap mouth. Oddly, it isn’t actually a carnivorous species (though it doesn’t seem to know that), and as long as it gets plenty of sunlight and regular watering, it just spits its victims out again after a day or two – smelling slightly of lettuce, and with a very strange story to tell!