Gunnera tinctoria aka Giant Rhubarb

Gunnera tinctoria is a large perennial in the Gunneraceae family. Gardeners call it giant rhubarb or Chilean rhubarb. Its native range covers central and southern Chile and southwestern Argentina. It grows beside streams, lakes, and rivers in damp ground. It also grows near wetlands, along woodland edges, and on moist bluffs. This is a plant of temperate regions.

Plants grow from rhizomes and spread into dense clumps. Garden plants reach about 6 feet [1.83 metres] tall and wide. Their huge leaves give the clumps a bold shape. Missouri Botanical Garden lists leaves about 3 feet [0.91 metres] across. The RHS gives a wider range of 3.3–6.6 feet [1–2 metres]. The rounded blades have deep lobes and strong veins. Stout leaf stalks bear prickles, and the leaves have sharp spines. These sharp parts can make close handling awkward.

Tiny red to red-brown flowers crowd onto thick, upright spikes. The main flowering season runs from June to August. Local climate can shift the timing of bloom. The RHS describes spikes about 1.6 feet [0.5 metres] tall. Missouri Botanical Garden reports flower stems reaching 3 feet [0.91 metres]. Small green fruits with red tints follow the flowers. The broad leaves provide most of the plant's visual impact.

In gardens, it needs rich soil with plenty of humus. Keep the soil moist to wet, but allow drainage. Part shade suits it best, and it tolerates wet ground. Missouri Botanical Garden lists USDA hardiness zones 7–9 and low maintenance. Its size suits pond margins and the edges of bog gardens. It also provides a strong accent in damp, partly shaded sites. That source reports no major pest or disease problems.

Its spread outside gardens is a more serious concern. It has become invasive in parts of Europe and elsewhere. The RHS lists UK controls and a ban on sale. It must not be planted or allowed to grow wild there. Plants For A Future lists young leaf stalks as edible. People peel them, then eat them raw or cooked. That source reports no known hazards, rather than proven safety. It also records astringent use of the whole plant. Roots supply black dye and tannin; leaves serve as roof coverings.