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Garden Improvement Information Series

Gunnera Plants & Gardening Notes

Gunnera is a genus of herbaceous flowering plants, some of these are gigantic. The genus Gunnera, was named after Johann Ernst Gunnerus (17181773), a Norwegian botanist.
The genus is the only member of the family Gunneraceae. The 40-50 species vary enormously in leaf size. Of the 45 or so summer-flowering species in the genus, there are drastic differences in leaf size.

DESCRIPTION: These perennials are mainly grown for their beautiful foliage. Gunnera (commonly known as the Giant or Prickly Rhubarb) isn't hardy in very cold climates; they are natives of South America, South Africa, Tasmania, Abyssinia, Java, New Zealand and Hawaii. The natives of South America eat the thick leafstalks of Gunnera manicata and Gunnera chilensis either raw or cooked; they are known as Pangue. The Rhubarb plant used to make pies, tarts, etc. is Rheum rhabarbarum.

Propagation can done by dividing the rootball or by the method most commonly used which is by dividing rhizomes, tubers, corms or bulbs, including offsets. Another propagation method used is by planting their tiny seeds. Tiny red-brown flowers are borne in erect panicles to 1m in height. followed by small red berry-like fruits. Sow these seeds in gentle heat as soon as ripe, seed quickly loses viability. Germination may be improved by maintaining very moist, but not wet, conditions and temperatures of 75-85 degrees Celcius. Germination should happen within two weeks. Germination may be slow and erratic, so prick out individual seedlings as they become large enough to handle and transfer to pots or trays. Over-winter in a cool, frost-free shed or greenhouse and plant out in April or May. Gunnera has roots that are host to microscopic blue-green algae, which convert atmospheric nitrogen into a soluble form of nitrogen that the plant can use for growth. NOTE: In Nature, water is the main way that the Gunnera seeds spread and colonize other areas. Birds are secondary.


Cyanobacterial Symbiosis:
In nature, all Gunnera plants form a symbiosis with a nitrogen-fixing cyanobacteria, thought to be exclusively Nostoc punctiforme. The bacteria invade the plant via glands found at the base of each leaf stalk[1] and initiate an intracellular symbiosis which is thought to provide the plant with fixed nitrogen in return for fixed carbon for the bacterium. This intracellular interaction is unique in higher plants and may provide insights to allow the creation of novel symbioses between crop plants and cyanobacteria, allowing growth in areas lacking fixed nitrogen in the soil.

Scientific classification:

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This web site was first published November 08, 2003.

This page was last updated September 22, 2018.