Poblanos are among the mildest chile peppers, and are also known as pablano peppers; they are sometimes mislabelled as pasilla peppers. Poblano peppers are black-green when immature and turn dark red with age. After drying, poblanos may be dark red (ancho chile) or brown (mulato chile). These thick-skinned peppers range between 3 and 5 inches (7–12.5cm) long and 2 to 3 inches (5–7.5cm) wide. They tend to have a shape that is roughly heart-like, and terminate in a blunt point.

Poblanos have a heat score that ranges between 1,000 and 1,500 Scoville heat units. How high a chile pepper scores on the heat scale is determined by high-performance liquid chromatography measurement of how many parts per million of capsaicin it contains. (Capsaicin is the compound that gives chile peppers their fiery bite.) This figure is then converted into the historic Scoville heat units that signify how much dilution is necessary to drown out the chile’s heat. The heat level of a chile is given as a range because it varies with how and where the pepper was cultivated.