How old do kittens need to be to give them catnip?

The question is in the title 

It's not harmful but younger kittens may not respond to it. Some cats are 6 months or older before they respond to catnip. You can try it. . .I've had kittens about that age who liked catnip, but he might not be ready yet.

Thanks Willowy 

You can also try a few different styles of scratching posts. My cat loves a cardboard one that is shaped like a saucer. Some cats like vertical scratching, etc. try placing them near other places he's scratching.

He's very cute!

My kitten is 3 months old and he's one crazy guy. A few weeks ago he didn't even look twice at the plant but today he pulled a leaf off and started to chew on it. He didn't eat any but I swear he's a little calmer. I was hoping it would go this way. Some cats get calm and other are a freak show! Good luck!!