The leaves of broadleaf cattail are sword-like and flat, exhibiting a gray-green hue. They are marked by parallel veins running the length of each leaf. In the fall, the leaves transition to a bright yellow color. These leaves can grow to a height of 5-8 feet (1.5-2.4 meters) and have a width ranging from 3/4 to 1.5 inches (2-4 cm). The distinctive structure and seasonal color change are key identifying characteristics.

The cylindrical flowers of broadleaf cattail appear in mid to late summer. The female flowers, located below the male flowers on the stalk, bloom from May to July. The flowers are favored in fresh and dried arrangements. Female flowers are densely packed, brown and velvety, measuring approximately 4 to 8 inches (10 to 20 cm) in length, and cylindrical in shape. Male flowers, situated above, are smaller, pale yellow, and club-shaped. The flowers lack a strong scent and are primarily grown for their unique texture and form.

Broadleaf cattail features tall, erect, and unbranched stems rising from robust underground rhizomes. The stems are cylindrical, smooth, and typically green in color. They can reach heights of up to 9 feet (2.7 meters), with a thickness of about 0.5 inches (1.3 cm). The non-branching stems exhibit a tough texture, providing structural support. Key identifiers include their erect posture and the connection to rhizomous subterranean stems, crucial for propagation and stability.

The fruit of broadleaf cattail is typically a dry, brown, densely packed cylindrical cluster, measuring about 0.5 to 1 inch (1.3 to 2.5 cm) in diameter and 4 to 6 inches (10 to 15 cm) in length. These fruits are composed of numerous tiny, wind-dispersed seeds encapsulated within narrow, elongated follicles. The surface texture is somewhat fuzzy due to the fluff that aids in seed dispersal. Each fruit spike matures during the summer and persists into late fall, aligning with the observed availability from June to November in regions such as North Carolina.