I don't know much about growing cardamom, though I did look into black cardamom a few years ago. I knew I wouldn't be able to grow it around here, but thought I may be able to at least get some leaves, which are aromatic, and are wrapped around some foods before grilling, in northern Thailand. The trees get to 5 meters, and require a much longer growing season than I have, and I gave up on the idea, since I couldn't find seeds anywhere. I was surprised that it is related to green cardamom (both in the ginger family), though a lot of its flavor comes from the drying method, giving it that smoky flavor. The pods are probably too large to air-dry, and rot, like thick fleshed peppers, and eons ago they probably began drying over fire, as with chipotles, and several other chiles, giving us these wonderful smoky spices.