T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Gunnera manicata (Giant rhubarb)

Kingdom: Plantae
(Unranked): Angiosperms
(Unranked): Eudicots
(Unranked): Core eudicots
Order: Gunnerales
Family: Gunneraceae
Genus: Gunnera
Species: G. manicata
Binomial name: Gunnera manicata
Common name: Giant rhubarb (Despite the common name, this plant is not closely related to the rhubarb and is not edible.)

Gunnera manicata is a native of South America from Colombia to Brazil. It is a large, clump-forming herbaceous perennial growing to 2.5 m tall by 4 m or more. It has with stout horizontal rhizomes. The leaves of Gunnera grow to an impressive size. Leaves with diameters well in excess of 122 cm are commonplace, with a spread of 3 m by 3 m on a mature plant. The undersides of the leaf and the whole stalk have spikes on them. In early summer it bears tiny red-green flowers in conical branched panicles, followed by small, spherical fruit. These flower stems look like tall red broccoli, with each seed head containing in excess of 80,000 seeds
This plant grows best in damp conditions such as coastal cliffs, stream banks and wetlands. In severe winter conditions the plant dies down but grows new leaves in spring. It is tolerant of salt spray and a wide range of climatic and soil conditions, therefore they are very invasive.
In New Zealand Gunnera manicata can reduce natural biodiversity and compete with native species. The large leaves prevent native species from growing underneath them. It can also impede water flow through the obstruction of drainage channels and wetlands. Gunnera manicata also displaces culturally important species for the Maori, such as edible watercress (Lepidium sativum) and flax (Phormium tenax).
All Gunnera species and hybrids – including Gunnera manicata and Gunnera tinctoria are plant pests. All Gunnera species share many of the same features and are commonly mistaken for one another. However, any confusion between these is unimportant because they are all troublesome plants that require the same control measures.