It's hard to give a good explanation of it. The first time I went to the ruins was out of curiosity. I talked to some NPCs every now and then before going there. I thought I might find something nice if I got far enough. Once I got to the dead end, I thought I needed a certain weapon to break through the vines. I returned there multiple times with different weapons and party members to try breaking the vines. I decided to leave and come back later upon realizing it was getting nowhere. From here on out, I did the normal stuff with affinity related events until I got the quest. It was then I started talking to a bunch of plant progeny like the quest says to. I went back and forth in the ruins hoping something would happen while raising the plant affinity. It was then at some point I got the dialogue talking about what was found in the ruins.