Water pepper is common in low-lying regions of NZ, growing on river banks and in marshy areas. It is also sometimes an aquatic plant in small clear streams.
Its name comes from its burning, peppery taste, which makes it unpopular with stock.
It is an upright anual, up to 80cm tall. It has red/purple stems, willow-like leaves, and smal greenish white flowers. The flower spikes are long and slender. It typically flowers from early Summer through until June.
It has bright green, unmarked leaves, which have a wavy edge can be up to 10 cm long. The leaves are quite narrrow and lance shaped.