Pampas grasses form tussocks up to 3 metres high with grey-green drooping leaves 2 metres long with very sharp edges. The flowering heads are dense, feathery and silver-white or sometimes dull pink at first, held above the leaves on reed-like stems. The forms with only male flowers planted in the 19th century could not move far from gardens. But the recent introduction of seed-producing forms threatens invasion of waterways, forestry plantations and native vegetation, where pampas grass displaces other vegetation and prevents access.