Gunnera is the sole genus of herbaceous flowering plants in the family Gunneraceae (order Gunnerales), a small, distinctive lineage of the core eudicots. The genus encompasses roughly 63 species distributed across a remarkably wide range that includes Latin America, New Zealand, Australia, Hawaii, Papuasia, insular Southeast Asia, eastern Africa, and Madagascar.
The genus is perhaps best known for the subgenus Panke, which contains some of the most dramatically large-leaved plants on Earth. Gunnera manicata, native to the Serra do Mar mountains of southeastern Brazil, is often cited as the largest: its reniform leaf blades typically reach 2.5 m (8 ft) in width, and the thick, succulent petioles can extend up to 2.5 m (8 ft) in length. Cultivated specimens in England and Ireland have produced leaves exceeding 3.3 m (11 ft) wide. Gunnera peltata of the Juan Fernández Islands can develop an upright trunk up to 5.5 m (18 ft) tall. Gunnera magnifica of the Colombian Andes bears the largest leaf buds of any known plant, up to 60 cm long. Beyond these giants, subgenus Panke also extends into Hawaii and throughout the Neotropics.
Not all Gunnera species are giants. Outside of Panke, the genus includes mat-forming plants with small leaves, such as G. albocarpa from New Zealand with leaves only 1–2 cm long, and G. magellanica from southern South America. African and Southeast Asian species occupy an intermediate size range. Flowers are consistently dimerous — two sepals, two petals (or none), two stamens (or one), and two carpels — and the massive inflorescences of the larger species can reach 2.3 m in length.
Gunnera was named in honour of the Norwegian botanist Johann Ernst Gunnerus. It was initially placed in the family Haloragaceae, but the distinctiveness of its morphology and biology — including its unique symbiosis with nitrogen-fixing cyanobacteria of the genus Nostoc within stem glands — led to the establishment of the monogeneric family Gunneraceae. This placement has been confirmed by the APG III and APG IV systems.
Etymology
The genus Gunnera was named in honour of Johann Ernst Gunnerus (1718–1773), a Norwegian bishop and botanist who made significant contributions to Scandinavian flora. The genus name commemorates his work in natural history.
Distribution
Gunnera species are native to a wide, disjunct range: Latin America (from southern Chile and Argentina north through the Andes to Costa Rica and Mexico), the Juan Fernández Islands, Hawaii, New Zealand, Australia, Papuasia, insular Southeast Asia, eastern Africa, and Madagascar. The large-leaved subgenus Panke is centred in the Neotropics and Hawaii, while small-leaved species predominate in New Zealand and southern South America.
Ecology
A defining ecological trait of Gunnera is its symbiosis with the nitrogen-fixing cyanobacterium Nostoc, housed within specialised stem glands. This association — unique among flowering plants — allows Gunnera species to colonise nutrient-poor, waterlogged soils. The genus typically grows in moist to wet habitats: stream margins, montane cloud forests, bogs, and coastal wetlands. The large Panke species can form dense stands that shade out competing vegetation.
Cultural Uses
The petioles of Gunnera tinctoria (nalca) from southern Chile and Argentina are eaten fresh after peeling, and are also used in salads, liquor, and marmalade; leaves traditionally cover the curanto pit-roasting dish. Gunnera perpensa is used in traditional medicine across southern Africa for obstetric and digestive complaints, as a wound dressing, and in beer-making; petioles, flower stalks, and leaves are also consumed fresh or cooked.
Taxonomy Notes
Gunnera is the only genus in the family Gunneraceae. Under the APG II system (2003) the family was placed in order Gunnerales within the core eudicots; this was retained by APG III and APG IV. An earlier optional arrangement grouped Myrothamnus in Gunneraceae, but current treatments place Myrothamnus in the separate family Myrothamnaceae (also in Gunnerales). The type species is Gunnera perpensa L. GBIF lists the order as Haloragales, reflecting an older classification. Note: in 2022 it was shown that plants widely cultivated as G. manicata are actually a hybrid, Gunnera × cryptica.
