Completed dracoid ruins area, escaped the flood, return to graveyard talked to priest, but no silver leaf trees grow

strange, as far as i remember the mandrake roots should transform to silverleaf plants after talking to the priests ghost. have you tried leaving and re-entering the graveyard (and talk to the priest again)? or you could try to reload a savegame before you talked to him and do it again.

You need to talk to the emperor, not the priest. He's the key to getting the Silverleaf.

I have the same problem, I talked to him and he didn't give it to me, all the mandragoras are still not transformed

I had to reload a save file and try random stuff between after the cave and talking to the ghost and the 5th time it worked