New Zealand Pigmy weed, also known as Australian Swamp Stonecrop, was originally sold in garden centres as an ‘oxygenating plant’
This species was first introduced for sale in England in 1927. Since the late 1970s it has spread rapidly north and west. Between 1970 and 1986, it was recorded in 33 10km squares in Britain and Ireland. It is now widespread in England, where it is causing difficulties.
A perennial herb that grows submerged in sheltered waters up to three metres deep or as an emergent on damp ground. It can form dense, virtually pure stands. It generally grows vigorously in sites to which it is introduced, rapidly producing high biomass, at the expense of the indigenous plant species; stands may become extremely dense