This green frog has rough skin, a back that tends to sag with age, and enlarged eardrums on male specimens. Like the Leopard Frog, it has paired vocal sacs and does not grow extremely large. It is usually darker in color, with blurred dark dorsal spots. Some larger specimens develop a light green net-like pattern. Dorsolateral folds are visible in some individuals and the belly is white, with the eyes turned slightly upwards. The feet are fully webbed, as this frog is more aquatic than most of its cousins.
The males have a unique call like that of someone knocking on a door, usually given three times in a row. It can sometimes be sped up to sound like a dull purr.
These frogs like to be in water, often around lily pads. One popular site at the Saint John's Arboretum is near the footbridge on Stumpf Lake, where a few males can call from the small “islands” in the swampy area in the lake.