buy catnip plant from culvers, what kind should i buy?

Culvers garden center has catnip seeds/plants... what species of catnip plant do you have? Would you recommend it? What grows the fastest?

I didn't realise there were different kinds of catnip. I bought seeds in the past from a big seed company here in Ontario, and I've just realised that what I planted was cat mint, as opposed to cat nip. Regardless, the plants have taken off in the gravel and return each year to get munched on by my cats. It was extremely easy to start from seed and they're very hardy. They grow in the gravel where only some weeds will sprout, they don't get much water, they survived the nasty winter with no ill effects, and they get continually ravaged by my cats yet they keep on growing!
I used to grow some in a pot too, but they couldn't withstand the constant attention from the cats. They were total "pot heads" and it was a pain trying to keep the pot out of reach.

I think cat mint is another name for what is also known as true catnip.  It's proper name is Nepeta cataria.  It's also sometimes call cats wort.   

I bought a nice big healthy catnip plant and it smells potent.I also got some cat grass so that he doesn't munch on anything he shouldn't (even though I put everything but cloth away)