I've never known anyone who's grown cardamom. There're both green (sometimes called white) and black cardamom pods. Far as I know, the seeds are the only part of the plant that's used. The black pods are larger, and have a milder flavor. The greed pods are small, but can easily be opened to retrieve the seeds. The seeds have a strong, very floral taste. I like it very much.
Ground cardamom is often used in desserts, though I only use it in savory dishes. The powder can be found in the spice department, and is quite expensive. You can save by ordering online. Depending on how much you need, it might also be cheaper to buy green cardamom pods--available online or at any Indian grocer--and grind them yourself.