Gunnera is a plant genus consisting of several dozen species that are native to South America and New Zealand. The name for these plants is derived from the Norwegian botanist Johann Ernst Gunnerus (1718-1773). One species that is particularly popular among gardeners and landscapers is Gunnera manicata. This perennial evergreen plant is commonly known as the giant rhubard, primarily due to its enormous leaves and extremely long stems. It grows up to eight feet in height and spreads a similar length. It naturally develops into clumps, which makes it an ideal specimen plant, especially in water gardens or bogs.
There are several things to consider when planting and growing the giant rhubard. The condition of the soil, the climate, and certain pests or diseases can affect the health of Gunnera manicata.
The natural habitat of G. manicata is very humid and moist. Typically, it is grown near a water source, such as a pond or lake. When planting it in a garden or using it in a landscaping project, ensure the soil is consistently moist.
This species is capable of surviving in hardiness zones seven to eight. It isn’t too tolerate of the cold since it suffers from frost damage during the winter. Partial sunlight is ideal for this plant.
Watering and Fertilizers
G. manicata is a high maintenance plant that requires regular watering to keep the soil moist. It is recommended to add a controlled release fertilizer to the garden soil to improve growth and development of the giant leaves and stalks.
The ideal time to divide the clumps of this massive plant is during the spring months. If done correctly, the newly established plant will sprout small reddish flowers between July and August.
Besides watering, pruning, and propagating, it is important to remove the dead leaves and stalks that have fallen around Gunnera manicata. They could provide a breeding ground for fungal spores, which could infect the plant.
Gunnera – Monrovia
Plant Finder: Gunnera – BBC Gardening