Acaena novae-zelandiae

Native to Australia and New Zealand, pirri-pirri bur, Acaena novae-zelandiae, is a short, creeping plant popular in container planting schemes and rockeries. It forms dense mats of lobed bronze leaves, from which ball-like heads of hooked seeds (burs) appear.

In recent years it has spread to the wild through seed and the dumping of garden material. It is now found in a variety of wild habitats including sand dunes, cliffs, heaths and disused railways, where it poses a threat to native plants. It's easily spread by seed via its hooked bur, and can be invasive. While Acaena species are not on the Government's list of invasive plants for England and Wales, they are considered invasive non-native plants in Northern Ireland, where it is an offense to plant or cause them to grow in the wild. In Scotland, it is an offense to plant any non-native plants in the wild.