I had some problems with my catnip "crop" last year.
Seeds germinate here and there around the yard but the mower and weed-whacker takes care of them. They haven't been like the mint and able to either duck or root off every stem.
I have had some nice plants around the large veggie garden. There, the mower/weed-whacker got a little too happy in 'o8. I would have liked to have had some for harvesting.
My level of sophistifaction* with other herbs for tea have gone up these last few years. So, I don't have quite the need to compete with the neighborhood cats over the catnip. Nevertheless, I'd hoped to have one nice plant. Nope, harvest would have required fingernail scissors after a few uncontrolled passes with the mowing equipment early in the season.
Steve
*The feeling of satisfaction gained by indulging or partaking in sophisticated pastimes, such as herb tea tastings, chamber orchestra recitals, gallery openings and transatlantic cruises.