Gunnera (Gunnera tinctoria) is a huge, splashy plant with leaves that can grow as much as 5 feet across and is sure to become a conversation piece in your garden. Gunnera is especially appropriate if you have a pond-side garden or a boggy place where the plant will stay constantly moist. Gunnera will survive an occasional light frost, but if you live in a climate with cold winters, you'll need to bring the plant indoors until spring.
Plant gunnera seeds outdoors when the weather warms in spring. Gunnera seeds won't germinate in cold soil. Choose a moist spot in full sunlight. Gunnera can tolerate light shade; the plant won't grow in full shade. If the soil is poor, work in 2 to 3 inches of manure or compost.
Keep the soil constantly moist. During warm, dry weather, water the plant daily and never allow the soil to dry out.
Fertilize gunnera weekly, using an organic fish emulsion. Apply the fish emulsion according to the directions on the label.
Mulch the gunnera plant in autumn if you live in a climate with mild winters. Spready 2 to 3 inches of organic mulch such as chopped leaves, pine needles or bark chips around the base of the plant.
Move gunnera to a large container before the weather turns cold if you live in a freezing winter climate. Use a large container with bottom drainage, and fill the container with commercial potting soil. Store the plant in a cool, frost-free room until spring. Keep the soil slightly moist.