I think envy can in some cases reflect a passion for collecting (which can in extreme cases become an obsessive disorder). Some men will know this from their childhood (or later) collecting stamps, coins or other items. There is often a want to 'complete a set'. That translates into plants as well, methinks. Once you have a few, say Salvias, you can end-up wanting more, then seeing as you've got most of them, you want the rest. That sort of thing. Hence if somebody you know has one of the ones you 'need', you'll be envious. I'm no psychologist; I don't know what it all means; to me it is just behaviour.
You can also be envious over knowledge - not just over possession. For instance, somebody may know the whereabouts of a rare orchid; you can be envious of that if you would like to see it. As well as that sort of general awareness, envy can apply also to technical skills such as grafting. But I think a distinction can be made. I, for instance, am useless at plastering a wall or puttying a window. But I am not envious of those who can. I admire them, because they succeed where I have tried and failed. I do not want or really need to do those things.
Back to possessions. The distinction between envy and admiration exists there, too. I can admire a huge 'Kiftsgate' rose, towering Wellingtonia, or rare Darlingtonia - perhaps even marvel in them. But I do not necessarily envy those who grow them. That may be because I know I could not do them justice, given my own circumstances - though that makes the distinction between envy and admiration a somewhat conscious choice. Or, in other cases, I may simply feel that those things are best appreciated in the wild - eg. Dodecatheons in damp forest meadows high in the Californian Sierra Nevada, Monterey pines on the rugged coast of the Big Sur, or sheets of Dimorphotheca in Namaqualand.
