Legal Question in Criminal Law in California

Since the days of Robin Hood people have been using public lands for their own private benefit, and since the days of the Sheriff of Nottingham this has been illegal. The legal question is easy. It's illegal (even if growing the same number of plants on your own property would be legal). You should be more concerned with the practical aspect. To keep your garden hidden from other forest visitors, you would have to travel reasonably far from the nearest public road. You would have to visit the site from time to time to water, feed, and trim your plants.

At best, you risk being ripped-off. At worst, your risks include encountering fellow clandestine horticulturalists, for example a well-armed gang of bikers, or members of the Mexican drug cartel, who will kill you dead rather than allow you to escape and reveal their location.

The fact that you can't 'think' of the basis of federal and state laws making 'cultivation' and ''possession for sale' felonies with mandatory sentencing, doesn't make the laws magically disappear or not apply to you. If you are caught cultivating anywhere, you can be prosecuted and end up in federal or state prison, or both. Even if caught only 'in possession' [small amount in your pocket] by federal agents, your little card does not immunize you from arrest and federal prosecution, as the card is not acknowledged by federal authorities as 'legal'. That card is a politically correct legal fiction in CA, meaning that CA "law enforcement" authorities have been told by CA legislature to look the other way and ignore your use and activities that are on the books as crimes. The feds are not bound by that instruction.