Gunnera tinctoria is a large perennial plant native to moist riparian areas in Chile. Commonly called giant rhubarb, Gunnera tinctoria develops large leaves that can grow more than 4 feet in diameter on thick, hairy stems. With a mature height of 6 feet tall, gunnera makes an excellent specimen plant for large gardens with plenty of space for the plant to grow. Gunnera is a hardy plant that thrives under damp conditions in U.S. Department of Agriculture Hardiness Zone 7 through Zone 11.
Locate a damp area on your property in partial shade to grow Gunnera tinctoria. The plants grow near streams, lakes and bogs in the wild and grow best when their roots have continual access to water. The plants tolerate areas away from running water, but require regular irrigation to maintain soil moisture in home landscapes.
Dig a hole large enough to accommodate the root ball of the Gunnera tinctoria plant you want to grow, and mix in one part compost to one part native soil. Compost helps retain soil moisture and provides supplemental nutrients for the plant to utilise throughout the growing season.
Loosen the roots of the Gunerra tinctoria specimen you are planting, and place them in the planting hole at the same depth as the nursery planter. Loosing the roots helps facilitate healthy root development and encourages new plant growth.
Backfill the soil around the base of the plant, and water thoroughly to settle the soil around the roots.
Apply a 2- to 3-inch layer of organic mulch around the base of the plant. Mulch helps prevent competition from weeds, and also helps to maintain soil moisture around the plant.
Irrigate the plants regularly throughout the growing season to maintain soil moisture. If the leaves start to turn yellow and wilt, increase the frequency and volume of water when irrigating your Gunnera tinctoria.
Prune back the stems of Gunnera tinctoria to the ground with sterile pruning shears in the fall after the plant has wilted. Cover the stems of the plant with the large leaves, and cover them with a thin layer of organic mulch to insulate the roots from cold temperatures during the winter.
Uncover the plant in the spring to allow new plant growth to grow freely through the soil. Gunnera tinctoria is a resilient perennial that will grow larger each year in your landscape.
Gunnera tinctoria is readily available from plant nurseries in a variety of sizes. Apply a general garden fertiliser in the late spring if the plants are struggling to grow in your landscape.