I can't tell you anything about which leaves came from old trees and which ones came from plantation bushes. I live in San Francisco, and I've never lived in China, so there's pretty much no way I'd be able to tell you that. I can only tell you what I like. I do not know if the teas I like are old tree, or tai di cha made to look like old tree, gu shu, lao shu, faux shu, ming qian, yu qian, or what. I only know what I like, and I know that I don't find it often. All of the teas I like are always *claimed* to be from old trees, almost always claimed to be first flush of spring, but the ones I like are a small fraction of the available teas that are claimed to be such. I can identify a few characteristics that I have observed in almost all of the young puerh teas I have liked. Here are my selection criteria:
1. PERSISTENT BUBBLE. When the tea soup is poured from the cha hai to the cup, particularly if poured into the middle of the cup & not the side, small bubbles come up in a ring formation, but they stay put. The bubbles do not migrate to the side of the cup, or even move much at all. If you jostle the cup, the tea soup sort of looks like shaken gelatin, as the bubbles jiggle but still stay in place. Persistent.
2. Strong, pleasant aftertaste & sensation of coldness in the mouth and throat that hangs around for a long time after drinking the tea. It took me a while to learn to recognize this sensation, but now it is unmistakeable & most teas simply don't have it. Sometimes I notice sweetness in the aftertaste of teas I like, and sometimes I don't, but this is not as consistently present as the coldness.
3. Yellow soup. Not orange. Not brown. Bright yellow. Say what you want about cup depth differences, but using the same cup & pitcher in comparisons of cup color between different teas, there is a blatantly obvious and consistent difference between the teas I like and the ones that don't interest me. I understand that maybe this is due to differences in how sha qing is carried out, and maybe due to differences in how wet the weather may have been prior to picking, but I don't care. I am talking about what I like, not what caused the thing I like.
4. Soup has a full-bodied mouthfeel, almost kind of thick. This characteristic seems to vary a lot depending on which vessel is used to brew the tea. I have no idea why.
5. If you smell the bottom of the cup after drinking the tea, particularly w/ the first couple of infusions, there are strong, sharp, sweet, honey/flower/perfumey sorts of smells. I have read that this can be faked in processing and is not necessarily an indicator that the tea is from old trees. To be honest, this characteristic isn't particularly important to me. I am only listing it because all of the teas I like seem to happen to have it. Among teas that do not interest me, it seems to be a less common characteristic.
6. Qi is unimportant to me. I have experienced very strong and relaxing cha qi after drinking tea that was just big factory plantation stuff, and even though the feeling was nice and all, I just didn't like the tea. I only drank it as an experiment to have a better idea of what's what. Thus, cha qi is something that, while I of course enjoy it, I don't find it particularly useful as a selection criterion and I don't think it tells me anything about the quality of the tea.
7. I don't care what the leaves look like. Not dry leaf, not dregs, none of it. I've had some very good teas that were composed almost entirely of small, broken leaf fragments. I've had some teas that had nothing but beautiful, perfect, complete two leaf one bud sets, with large, long leaves whose edges had serrations that varied greatly in size, but were totally bland and uninteresting. It would seem that gu shu trees that are over picked might, in their fourth or fifth + flush produce beautiful leaves that have very little flavor or power. However, it doesn't matter to me why this happens. I am only trying to identify characteristics that are useful to me as selection criteria; not explain them. I acknowledge that the good fragment teas I've had are only good for the first few infusions and they run out of gas very quickly, but they are still a lot better than tea that looks beautiful but has no oomph.