I wash mine in a sieve and place them in the sun to dry.
Out here that only takes about 4 hours.
I then place it in ziplock freezer bags and freeze it.
I have it growing like weeds out in the yard. Today dd brought some inside for the cats. I walked into the kitten room, and Sugartoes (Momma) and the babies Twinkie and Smartie were all rolling around on their backs. I said, "Lexie, did you give the kittens catnip?" She said, "No, I just let them smell it, and gave it to their Mom."
Well, happy eight week old birthday to you, they are all hyped up on catnip! She knows not to give it to them or their Momma anymore. Silly girl!
Every spring when i go to get flowers for the patio pots i pick up some cat nip. It is in with the herbs. I stick it in a big pot with some flowers, ornamental like. I never thought about freezing it? good idea.