Gunnera monoica

The genus Gunnera is the only member of the family Gunneraceae and contains 63 species. You are probably familiar with the giant rhubarb, Gunnera manicata, native to the Serra do Mar mountains of southeastern Brazil. You may not be as familiar with its diminutive cousin from New Zealand, G. monoica. Whereas G. manicata can achieve giant leaves approaching 2 meters across and is an impressive garden giant, G. monoica’s leaves are a comparatively tiny 2-3 centimeters across.

G. monoica is a stoloniferous groundcover that thrives in average to moist, humus-rich soil. The spreading rhizomes form a dense mat reaching 4-6 inches tall. It is evergreen at temperatures above 22°F and deciduous down to 0°F, or even colder with protective mulch. G. monoica grows in full sun to part shade. Its dark green, fleshy leaves are coarsely dentate and often hairy. Inconspicuous white flowers form in late spring but are hidden among the leaves. Tiny white fruits form in early summer. There is a bronze form in cultivation, though I have never seen it personally. It is high on my most-wanted list, though.

A very interesting symbiotic relationship between G. monoica and the cyanobacterium Nostoc was reported in the journal “The New Phytologist” by Paul Stock and Warwick Silvester from the Department of Biological Sciences at The University of Waikato, Hamilton, New Zealand. The article titled “Phloem transport of recently-fixed nitrogen in the Gunnera-Nostoc symbiosis” describes how G. monoica is at least partially nourished by the symbiotic Nostoc blue-green bacteria. I know, kind of nerdy, but fascinating!

G. monoica is native to New Zealand and the Chatham Islands. It was first described by Etienne Raoul, a French naval surgeon and naturalist who published “Choix deplantes de la Nouvelle Zelande” (Selected Plants of New Zealand) in 1846. The genus Raoulia was named after Raoul. Raoul Island, part of New Zealand, was named after his uncle Joseph Raoul. History aside, G. monoica is an uncommon but beautiful and useful landscape plant in USDA Zones 7-9 and a great container plant everywhere.