Gunnera manicata is a large, clump-forming herbaceous perennial growing to 2.5 m (8 ft) tall by 4 m (13 ft) or more. The leaves of G. manicata grow to an impressive size. Leaves with diameters well in excess of 120 cm (4 ft) are commonplace, with a spread of 3 m × 3 m (10 ft × 10 ft) on a mature plant.The largest on record had leaves up to eleven feet (3.3 meters) in width.^[6] The underside of the leaf and the whole stalk have spikes on them. In early summer it bears tiny red-green, dimerous flowers in conical branched panicles, followed by small, spherical fruit. Like most gunneras, it has a symbiotic relationship with certain blue-green algae which provide nitrogen by fixation.

Despite the common name "giant rhubarb", this plant is not closely related to true rhubarb. It was named after a Norwegian bishop and naturalist Johan Ernst Gunnerus, who also named and published a description about the basking shark.^[7]

Gunnera manicata is native to the Serra do Mar mountains of coastal Santa Catarina and Rio Grande do Sul states, Brazil, where it is used in traditional medicine for sexually transmitted diseases.^[8]

In 2022, it was shown that plants in cultivation under the name Gunnera manicata in Britain and Ireland, and likely elsewhere, were actually a hybrid, Gunnera × cryptica.^[5] It is primarily cultivated for its massive leaves.^[4] It grows best in damp conditions such as near garden ponds, but dislikes winter cold and wet.^[9]

In December 2023 it was announced that Gunnera × cryptica (usually grown as Gunnera manicata) was to be subject to a ban in the UK, meaning it cannot be sold or cultivated, and those who have it in their gardens must ensure it does not spread.^[10][11]

• Pink, A. (2004). Gardening for the Million. Project Gutenberg Literary Archive Foundation.
• Gunnera manicata