Black Cardamom and Green Cardamom Pods are related, but they are not interchangeable in flavor. Green cardamom is usually floral, citrusy, sweet, and perfumed, which is why it works so well in chai, desserts, rice dishes, and bright spice blends.
Black cardamom is larger, darker, and much more savory. Its pods are traditionally dried over fire or in smoke-fired systems, so the flavor is smoky, earthy, resinous, piney, mentholated, and slightly camphorous. Use green cardamom when you want lift and perfume. Use black cardamom when you want smoke, woodsy depth, and slow-cooked savory complexity.