Last winter my cat died. It wasn't a huge deal for me because he lived with my parents. He was very old, close to 20 actually. I got him as a kitten when I was 10 or so. He was an indoor/outdoor cat so his age was even more astounding. Most of our cats only live for around 8 years.
Anyhow, my mom kept a catnip plant for him and whatever cats we had at the same time. She even transplanted it when we moved. He hoarded it. He would lie in the bush and eat it and swat at anything that came near. He'd get sluggish and drugged up and snag my pant legs with a single claw. It was very clearly his catnip.
My mother informed me that this spring the perennial catnip did not return. Apparently Patrick and the catnip were symbionts.