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Gunnera [guh-NER-uh], is a genus of flowering plants belonging to the Gunneraceae family.
Gunnera is the only genus in the perennial family and contains 63 different species.
Many of these species contain very large leaves, some measuring up to 10′ feet in size.
Gunnera plants are mostly native to warm climates south of the Equator.
Various species come from Australia, New Zealand, Hawaii, Southeast Asia, southern Africa, Madagascar, and Latin America.
The most popular of the species is the Gunnera manicata [mah-nuh-KAH-tuh].
Known as the giant rhubarb of Brazil or dinosaur food, the plant produces clumps of growth up to 8′ feet tall with leaves measuring over 4′ feet.
Here’s a closer look at the recommended plant care techniques for giant rhubarb and other Gunnera species.
Gunnera Manicata Care
Size and Growth
Gunnera plants often produce extremely large leaves and may cover a lot of ground.
For example, the giant rhubarb has leaves measuring 4′ feet across and reaches a height of 8′ feet with a spread of 13′ feet or more.
The leaves are rounded with thick stalks on the undersides.
Flowering and Fragrance
Some species of the giant rhubarb produce spikes with tiny red-green flowers appearing for a short period in the early summer.
The flowers are often followed by the growth of small spherical fruit.
However, people primarily cultivate Gunnera manicata plants for their large, showy leaves not the fruit.
Light and Temperature
Grow Gunnera in full sun or partial shade. It prefers brighter conditions during hot, wet summers and more shade during the cooler winters.
The manicata gunnera comes from a warm, humid region and cannot survive freezing temperatures throughout the winter.
Gunnera grows best in USDA hardiness zones 9 to 11.
In zones 6 to 9b, the plant may survive the winter outdoors with proper protection.
To protect young Gunnera plants from the cold, cover the growth with several inches of dry leaves or mulch.
- Use a tarp to keep the organic layer from blowing away.
- Cut down mature plants to within 12″ inches of the roots.
- Pile the cuttings on top of the plant to form a canopy or tent.
- The cuttings should protect the plant from freezing conditions.
- In spring remove the dead cuttings and leaves to allow for the new spring growth to develop.
Watering, Feeding And Soil
If grown in the right environment, with moist soil watering is rarely needed.
Gunnera grows best in damp, marshy areas where the ground remains wet throughout the warmer months.
When grown in a garden without constant moisture, water the plant regularly to ensure the soil never dries out.
Fertilizer isn’t necessary.
Outside of marshy areas, use a combination of clay, garden soil, and compost to provide rich soil for the plants.
If growing Gunnera plants in a cool region, cut it back in the fall and use the cuttings as cover for strong winds and freezing temperatures.
Trimming plants back also helps manage growth and keeps the plant from expanding out of its intended growing area.
How To Propagate Gunnera Manicata
Propagate Gunnera by division or seeds.
Collect seeds from the cone-shaped flowers of a mature plant or purchase seed packets.
- Plant the seeds directly in the ground, pressing them an inch or two into the soil.
- Sow seeds about 6″ – 8″ inches apart. Keep the seedlings moist.
- When the seedlings reach about one foot tall, thin them to about 5′ – 10′ feet apart.
Propagate by division after the plant finishes blooming.
- Dig up the soil around the root ball the crown and carefully lift the rhizomes.
- Separate the sections of the rhizome by hand and cut using a sharp knife.
- Plant the separated rhizomes in prepared sites using marshy soil or clay/soil/compost mixture.
Gunnera Pest or Disease Problems
The biggest threats to Gunnera plants include slugs and scale insects.
Scale insects are small and have protective outer shells.
- Remove these pests using cotton swabs dipped in rubbing alcohol.
- For serious infestations, treat the plants with insecticidal soap or Neem oil.
Slugs may eat away at the leaves, but rarely permanently damage the plants.
Use slug bait to keep the slugs away or pick them off manually.
Depending on the species, keep the plant away from children and pets.
Some species of Gunnera are extremely toxic to eat and resemble the edible rhubarb plant.
For example, Gunnera tinctoria is often called the “horror plant” due to its extreme toxicity which may prove lethal if ingested.
However, the popular Gunnera manicata doesn’t contain any known toxic effects.
Additionally, some of the toxic species are invasive in certain regions.
The horror plant produces leaves measuring up to 6′ feet and may take over large areas of land if left to grow wild.
Suggested Gunnera Uses
Due to the size, Gunnera is best grown near the peripheral areas of the yard, garden or landscape.
It grows well in wet, marshy areas with lots of space for the massive leaves to spread.