They hatch at around 30 cm (11.8 in) and average at around 110 cm (43.3 in) to 150 cm but can grow up to 200 (225) cm (78.7 in). They are dark, long, slender, and typically about bronze in color with smooth scales that give them a metallic sheen. Juveniles can easily be confused with juvenile Grass Snakes, also having a yellow collar on their neck that may persist for some time in younger adults. Juveniles are light green or brownish-green with various darker patterns along the flanks and on their back. They appear to have two darker patches in the form of lines running on the top of the flanks. Adults are much more uniform, sometimes being olive-yellow, brownish-green, sometimes almost black, with no distinct sexual dimorphism in coloration. Often in adults, there may be a more or less regular pattern of white-edged dorsal scales appearing as white freckles all over the body up to moire-like structures in places, enhancing the shiny metallic appearance. When pale in color, sometimes two darker lines can be visible. The belly is plain yellow to off-white while the round iris has amber to ochre coloration. Both melanistic and albinotic natural forms are known, as is a dark grey form and even erythristic specimen. Males grow significantly longer than females. Maximum weight for German populations has been 890g for males and 550g for females (Böhme 1993; Gomille 2002). Lifespan is estimated at about 25 years or more.
Scale arrangement includes 23 scale rows at mid body (rarely 19 or 21), 211-250 ventral scales, a divided anal scale and 60-91 paired caudal scales (Schultz 1996; Arnold 2002). Ventral scales are sharply angled where the underside meets the body, which enhances the species' climbing ability.
