Round bur-like flower heads and strap-like leaves distinguish bur-reeds. Spiny flower heads grow on the sides of flowering stems, that bend at each point of attachment giving them a zigzag appearance. Narrow leaf bur-reed is highly variable with leaves ranging from ribbon-like underwater or floating leaves to stiff emergent leaves. Giant bur-reed is an emergent plant that can grow to over 2 m tall. Other, less common, bur-reeds are also found in Washington.
Leaf: Long, narrow, thick and spongy toward the base, alternately-arranged with parallel veins. Narrow-leafed: submersed, floating, sometimes emergent, 20-80 cm long (occasionally longer), to 1.5 cm wide. Giant: usually emergent, more robust, triangular in cross-section at the base, to 2.5 m long, 0.6-2 cm wide.
Stem: Narrow-leafed: submersed, floating, or emergent to 1 m long; usually not branched. Giant: emergent, 0.5-2.5 m long, with 2 to 5 short branches supporting the flower heads.
Flower: Emergent on slender, round stems. Female flower heads are spiny, round balls that turn from green to brown as they mature. Small male flower heads are located above female heads. Narrow-leafed: 2-4 female flower heads, lower female flower heads usually on short stalks; 2-5 male flower heads. Giant: 1-6 female flower heads, 5-12 male flower heads on stem branches. Blooms July to August.