Single flowers occur in dense clusters in May to mid-June or August. Inflorescences are green or slightly purple at first, then become tan.
Seeds are shiny brown.
The species growth form is highly variable, sometimes reclining at the base and rooting at the nodes. The amount of shading may also affect growth form. A Eurasian ecotype that is difficult, if not impossible, to distinguish from the native ecotype has also been introduced widely for forage and hay. It differs from orchard grass in that reed canary grass's leaves are much wider, the inflorescence is more narrow and pointed, and the individual flowers have a different shape. Reed canary grass should be accurately identified before attempting any control measures.