Members of the family Juncaceae are called rushes. They look a lot like grasses but only memebers of the family Poaceae are true grasses. You might also confuse rushes with sedges which are members of Cyperaceae. Like most sedges, rushes grow in and around water. Juncus effusus is a perennial rush whose hollow stems grow up to 3 feet tall. The flower heads appears along the stems. It's native all over the Northern Hemisphere.