Not sure how active it is still as I haven't really checked, but you can check out "Tree Hunt" FC to see if they're still kicking around.
Otherwise, click on "Look at" on an inactive crystal tree (right click > look at), and if you look at a map of where they are located, you can usually find your way to an active tree.
All the dots within the diamond/rhombus are crystal tree locations. It'll usually give you a hint like "north and to the west" -- you just head in that direction according to the map below.

e/ w103 Observatory is active at the current moment
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Quote (Jupe @ 15 Sep 2021 15:40)
pretty sure the only fcs out there are for furry erping
Pretty sure you were in that fc if I recall correctly
Lol cmon Jupe, the spam in all the RS3 topics is starting to get old.
This post was edited by Beacon on Sep 15 2021 02:34pm