New zealand pigmyweed

Description

Crassula helmsii, known as swamp stonecrop or New Zealand pigmyweed, is an aquatic or semiterrestrial species of succulent plant in the family Crassulaceae.Originally found in Australia and New Zealand, it has been introduced around the world. In the United Kingdom, this plant is one of five introduced invasive aquatic plants which were banned from sale from April 2014. This is the first ban of its kind in the country.It is on the Global Register of Introduced and Invasive Species of eleven countries. The shoots are rather stiff, carrying narrow parallel-sided leaves in opposite pairs, each leaf being about 4–24 millimetres (0.16–0.94 in). Small white flowers with four petals are produced in summer on long stalks arising from the upper leaf axils. The flowers are always above water.This plant from New Zealand has recently been recorded in waste ground waste site in Ireland at Howth Head, County Dublin.The plant grows on the muddy margins of ponds where it forms carpets with 100% cover, or semi-submerged in deeper water, or totally submerged with elongated stems. It does not die back in winter. It has been reported to be very tolerant to copper toxicity and to be a hyperaccumulator of copper.