Gunnera plants are referred to as dinosaur food or giant rhubarb for good reason. The plants are huge, easily growing up to 8 feet tall on prickly stalks and producing leaves measuring 6 feet across. Long reddish-green spirals of florets grace the gunnera plant each spring. Plants this large and dramatic add a whole new dimension to a garden. The gunnera plant requires attention to placement in the garden, soil preparation and lots of nourishment throughout the season.
Select a planting site that is sheltered from the wind, receives 6 to 8 hours of sunlight each day with moderate shade. The gunnera requires shelter from winds that dry the leaves. Locate gunnera near a water source that continuously keeps the ground moist.
Prepare the planting site with deeply cultivated, well-draining and moist soil heavily enriched with peat moss or rotted manure.
Mulch the area around the gunnera with 4 inches of organic mulch, such as peat moss, straw or wood chips to retain moisture in the soil.
Water the gunnera each morning during the summer, if there is no other supply of water, by overhead sprinkling until the soil is moist down to the roots. The gunnera plant needs its roots kept moist for good growth. The gunnera will thrive near a water source, but if it's not near one, pay close attention to watering thoroughly and frequently.
Fertilize the gunnera with a slow-release high-nitrogen fertilizer three times per year, beginning when the new growth starts on the plant and as indicated throughout the season.
Cut the plant back to the crown after the first frost and use the leaves or mulch up to 12 inches.