As requested by Espen204 here's an updated map with Oleander Sage locations if you guys/gals would like any other additions please feel free to send me a message. Happy trails y'all! :
Oleander Is a Beautiful But Poisonous Shrub | HGTV
RDR2 Oleander Sage Online Locations for Daily Challenges (Red Dead Online) - YouTube
Oleander Sage's location for today's challenge : r/RedDeadOnline
Finally found some Oleander Sage in my yard...time to make some poison arrows : r/RDR2
Red Dead Redemption 2": Herbalist Challenges - LevelSkip