Nepeta cataria. Not just for cats! Tall pink and white flower spikes are great in fresh and dried arrangements. Use the leaves in salads, sauces, teas, and soups - and of course fresh or dried for the cats! Catnip seeds are a good choice for a bee attractor that works well in containers on cat-free balconies. Protect seedlings from cats.
Catnip (and a few of its close relatives) contain the compound nepetalactone, which is extremely attractive to domestic and wild cats. It has the same effect on leopards, lynxes, and tigers as it does on house cats. Roughly 33% of all cats do not respond to catnip, and the response is believed to be hereditary.