i planted some from seed a few years ago, and it hasn't died yet! it just lives outside, and gets watered when i remember.
not too sure it is the healthiest.... as healthy catnip spreads like wildfire... but, its still around! every winter it looks like it dies, but in the spring it comes back.
the cats love it - but you have to remember to smoosh the leaves for it to work. if you were planting it now, i'd probably start it off inside, and then gradually move it out when it gets warmer. i think??? i may have done that with mine.
i have also tried to grow valerian, but that was far, far less successful.