When this clump of Thalia geniculata (Alligator Flag) was first planted, it was so small but see how much it has grown.
It is now a huge clump that started off with it sending its suckers down into the fluctuating water level. Its flowers are pendulous, unlike the Thalia dealbata with more upright flowers.
Its common name likely came about because in the alligator infested waters, the rustling of the plant is an indication of an approaching alligator. Interesting?