Green Pasillas, AKA poblano, are of the species, Capsicum annuum, and the fruit of the pepper plant—which is also known as a pod. Green Pasilla chile peppers are cultivated as a fresh market chile, canned and dried.
Green Pasilla chiles are one of the most complexly flavored mild to medium heat chiles. The Green Pasilla is a mild to hot chile with a hotness measured in the Scoville scale at 1,000 to 2,000 heat units. At their peak ripeness, their elongated, heart shaped, curved and contorted pod is glossy, deep green and thick. The chile contains a cotton-textured membrane laden with small white seeds. When cut, the chile's aromas reveal a preview of its flavors: spicy, earthy, rich and bright. Cooking the chile brings out more flavor profiles, offering depth and undertones both smoky and savory. Aged and dried forms of Pasillas become significantly warmer and develop more depth in flavor.
Green Pasilla pair well with other chile flavors such as guajillo and chipotle, herbs such as cilantro, epazote and oregano, earthy flavors such as mushrooms and cheeses such as feta, Gorgonzola and pecorino.
Outside of Northern Mexico and America, the name Pasilla refers to a dried chilaca chile (meaning little raisin). A dried chilaca chile is long and black, mild and earthy. Depending on the region the names are used interchangeably. When the Green Pasilla chile is dried it is referred to as a "dried ancho.”
Green Pasilla chiles originated in the Puebla region, south of Mexico City. It is one of the most common Mexican chiles in both Mexico and American states bordering Mexico. Green Pasilla chile peppers prefer warm, hot and dry climates and require long days of sunlight, thus preferring warm growing regions and summer growing months. They take quite a long time to grow, averaging 200 days from cultivation to harvest. Cold periods and dark days not only hamper the growing season, but they may also prevent a crop from reaching maturity.
Source (edited): specialtyproduce.com