In the 60s hippies fled to the backwoods of northern California to grow pot. There they have been joined by growers of 'medical marijuana' – available with a doctor's recommendation – as well as by Mexican drug cartels. With cannabis now its largest cash crop, the state will soon vote on whether to legalise it fully – and even Governor Arnold Schwarzenegger is thinking the enormous tax revenues might just solve his budget deficit… 'When I see that, it's like looking at a shed full of cows. I see a whole lot of work," says Jim Hill, opening the little gate into his humid greenhouse in which a forest of marijuana grows, and from which a pungent, heady scent exudes at gale force. Not work as in hard labour, emphasises Hill – though there is a bit of that – but expertise growing some of the most potent weed on the planet.