How many plants did you have? I believe gardening is a major offence if the purpose is to sell drugs and if the production is significant, but if it's just some few plants, then probably it's no big deal. Bringing the case for the court and eventually putting you in jail would be a very costly affair, the police did the right thing, saving taxpayers money from being wasted :-)

I believe the police is generally very lax on drug usage here, perhaps they have simply given up fighting a "war on drug usage". There aren't enough policemen, enough capacity in the courts and enough jails for "cleaning the streets". I believe that if you had hundred plants, then the police would have been very happy to jail you up, and there would have been a small notice in the newspaper about the police busting a "major drug producer" :-)