The smooth green snake is found in marshes, meadows, open woods, and along stream edges, and is native to regions of Canada, the United States, and northern Mexico.

The smooth green snake will often bob its head in order to mimic vegetation blowing in the wind.

[3] In size, it is classified as a "small medium" snake,[4] reaching to 36–51 cm (14–20 in) in total length (including tail) as an adult.

[9] The dorsal coloration can also vary depending on location: bluish in Kansas, olive-tinted light brown in southeastern Texas, and bronze in northern Wisconsin.

[12] O. vernalis is hunted by various predators, including the red-tailed hawk, great blue heron, rough-legged buzzard, bears, raccoons, foxes, and the common house cat.

[6] Habitat destruction is caused by road building, logging, cattle grazing, and the draining of streams.

The effects of livestock grazing include the reduction of grass, changes in tree species, compaction of soil, and more erosion, which affect the reptile population in these areas.

While there is some research showing the population of the snake is declining, only a small number of states (Iowa, Missouri, Indiana,[16] Michigan,[17] North Carolina, Montana, Wyoming, Nebraska, Colorado and Texas[18]) protect the smooth green snake with conservation laws.

[6] O. vernalis can be found in many different habitats, including marshes, meadows, the edges of streams, and open woods.

During hibernation, the smooth green snake looks for burrows, ant hills, and other dug-out underground areas, normally gathering in large numbers.

[9][19] Being cold blooded, it prefers warm areas, lying in the sun on rocks and logs, also using them for hiding.

The flicking of the tongue gathers air near the snake's head, and the Jacobson's organ (on the roof of its mouth) interprets the airborne pheromones and chemical signals.

The smooth green snake mostly eats insects and spiders,[3] including spineless caterpillars, harvestmen, moths, ants, snails, worms, and slugs.

Sexually mature smooth green snakes mate in the late spring or summer, and gravid females lay eggs from June to September.

[6] Smooth green snake eggs are white and oval; they have thin shells and are about one inch (2.5 cm) in length.