Gunnera manicata Brazilian Giant-rhubarb

A very large perennial with massive leaves, sometimes over 2m in diameter on thick stalks which are covered in spines and bristles. The inflorescence,which appears from the base of the leaves is like a large upright, club-shaped catkin, with male, female and hermaphrodite flowers mixed together. Giant-rhubarb (Gunnera tinctoria) is similar, but its leaves are smaller, more raggedly-cut, on stalks that don't have spines. It is planted frequently near water but also in drier places. It is long-lived and will persist as a relic of cultivation but does not spread by seed. Gunnera species pose problems as invasive aliens and they and their putative hybrids were named as species of concern in 2017 and of special concern under the Invasive Alien Species Order, 2019. It is currently an offence to plant Gunnera species or otherwise cause them to grow wild in the UK.

Neophyte

Gunnera is the only genus of flowering plants that has a intracellular host relationship with nitrogen-fixing cyanobacteria, uaually a species of Nostoc. The cyanobacteria reside in specialised stem-glands which are prevalent when plants are grown in nitrogen poor soil. This symbiosis is beneficial to Gunnera in that allows plants to make use of atmospheric nitrogen through nitrogen-fixation, mediated by the cyanobacteria. Interestingly, stem-gland production is supressed when plants are fed with combined nitrogen, e.g nitrates or ammonia.