In some recipes, the use of cardamon pods is required. In general these recipes don't specify which type (green or black) to use. So which one do I use when not specified in recipes?
Green cardamom pods tend to be more widely used in Western cooking and in all of Nigella's cookbooks if cardamom pods are mentioned they are the green cardamom. We suspect that most cookbooks will mean green cardamom when they refer to just cardamom pods.
Green cardamom tends to be quite expensive as the plants the pods come from are quite low yielding. It can be used in both sweet and savoury cooking and is the cardamom used in ground cardamom. Unless you are using large quantities of cardamom we would suggest buying the pods and grinding or crushing your own as the pods keep much better than the ground powder.
Black cardamom (sometimes called brown cardamom) pods tend to be larger and fatter than the green variety and traditionally they were dried over open fires, giving them a smoky flavour. They also tend to have a slight menthol aftertaste and are usually used in savoury cooking. They are often used in garam masala and for dhal or pilau rice.