A little late to the conversation, but there has been some evidence to suggest high elevation and high uv do in fact enhance the growth of trichomes and terpenes in not only marijuana, but herbs as well. There's also the common opinion that varieties of Papaver Somniferum (opium poppy) that grow in high elevations naturally, produce more alkaloids such as codeine and morphine than their lower elevation cousins... I don't know about that, but it is something poppy heads say. In terms of cactus, outdoor, weathered and wild peyotes are also said to contain more mescaline than anything grown indoors could hope to have. And recently there was a study where people grew seeds of high altitude, low water desert chiles, both in their place of origin and in Hawaii. The ones in Hawaii grew much bigger and lusher and easier, but had much less flavor and less heat than the ones grown in the high desert. I think things will always prefer their native regions, because that is the kind of plant they are... I mean, there's a reason cacao grows in the rainforest and not Canada... it's a rainforest plant... but there might be something to environmental stress that makes plants become more potent.