The Common Reed (Phragmites australis) is found throughout the world and is for the most part is considered invasive -- although it may have come to the new world long before humans. It is most commonly found in freshwater wetlands and edges of brackish marshes.
Phragmites are able to outcompete other marsh vegetation by blocking sunlight and producing extensive root systems. It also produces two toxins that deter other plants from sprouting.
They do, however, have their good points. They provide excellent habitat for marsh birds. And, they have been used in natural water purification systems and in basket making.
