Largest Plant Australia. The incredible accidental discovery of the world’s largest plant was discovered off the coast of Australia; with genetic testing, scientists found that a large seagrass meadow off the west coast is actually a single plant. In this article, learn about the World’s largest plant of 200 Km2 in Australia – Australian Posidonia … Continue reading World’s largest plant of 200 Km2 in Australia – Australian Posidonia (Posidonia australis)