Acquired it's common name because the leaves, opposite each other on the stem, join to form a "cup" that holds water, this feature allows birds to have a little drink. A tall specimen that sports many bright, yellow blossoms. Later in the growing season they will turn to seed which attracts birds such as goldfinches.
May not be suitable for all garden situations as it is rather vigorous and tall. Ensure it has room to spread out and avoid overwhelming lower growing species.
