Gunnera tinctoria Giant-rhubarb

Siimilar to Brazilian Giant-rhubarb (Gunnera manicata) with very large leaves, but not as large as those of that species and with stalks that have a thick covering of bristles but no spines. The stout, upright catkin-like inflorescences are also shorter, up to 50cm high. It was introduced as a garden palnt in1845 and was first recorded in the wild, in Guernsey, in 1884. It is frequently planted near ponds and other water bodies and will persist as a relic of cultivation. Furthermore, it has a formidable rhizome system which allows it to spread vegetatively and form large thickets so that large clonal populations become well established and invasive. It will also set seed and self sow. Consequently, Gunnera species (and their putative hybrids) pose problems as invasive aliens and 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 have 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.