Eichhornia crassipes, the invasive water hyacinth

The leaves of the water hyacinth, Eichhornia crassipes, growing in rosettes, are broadly ovate to rounded in shape, thickly leathery and glossy green. Leaf diameter is from 10 cm to 20 cm.

The leaves float above the water on spongy, bulbous stalks. When a patch of leaves becomes dense and largely stationary, not moved vigorously as in a river, its height upon the water may reach 1 m. The feathery roots, dark purplish to black, hang freely in the water below.

The inflorescence grows in a single spike of eight to fifteen flowers upon and erect stalk. The six obtusely pointed petals are pale lavender to pink.

Where the plants are indigenous their pollination is done by long-tongued bees. Should the pollination not go well in a newly invaded area, vegetative propagation by cloning works more than well enough to render this plant more than an ordinary nuisance (http://plants.ifas.ufl.edu; Wikipedia).