Gunnera can be propagated by division or by seed.
Division
Prepare: Sterilize tools to prevent disease.
Dig: Gently dig around the plant, being careful of the roots.
Identify divisions: Find the natural divisions in the plant.
Separate: Use a sharp tool to make clean cuts, ensuring each new section has roots and foliage.
Replant: Move the new sections to a new location with fresh, well-draining soil.
Water: Water well and keep the soil moist.
Protect: Protect the new plants from harsh sunlight and frost damage.
Seed
Harvest: Wait for the plant’s panicles to produce ripe, red fruits.
Collect: Open the fruits over a container to collect the tiny black seeds.
Sow: Lightly sow the seeds in a flat of moistened compost mixed with vermiculite or perlite.
Germinate: Cover the tray with plastic or glass and place in a warm location.
Transplant: Once the seedlings have germinated, transplant them to a new location with well-draining soil.
Gunnera is a heavy feeder that needs lots of water and organic material. It can grow in full sun to partial shade, but it’s best to plant it in low ground near water.