Random people going into secluded place is the benchmark of horror genre. Star Leaf, to its credit, decides the motive should be finding weeds. This is not so much a horror rather than a parody of one, it's utterly bizarre and often doesn't make much sense. Characters are partially product of satire, and it's confusingly insipid since it opens up with heavy theme of homicide and kidnapping. The best it could come up with is a few giggles due to its extreme oddity.
Three people go into a forest to find a mysterious sage who can lead them to a promised place of rare medication plant. Bizarre as it may sound the following is even crazier with trippy creature or haunting dream. This may very well meant to be representation of being high, nearly everything is pointless gibberish. Fortunately, the runtime is rather short, so it's equivalent of a weird dream.
Characters would appear out of nowhere, then disappear in five minutes as there's no consistent plot here. One can actually randomly skip a scene or reverse them and it would be the same incoherent story. Characters themselves are not likable, they are created for such intended effect with hippie gibberish and blatant reference to pop culture. The most sensible of them is surprisingly the jock stereotype, and even he seems woozy at times.
Star Leaf's best chance at entertainment is if audience is lenience and laugh at its silly antics. For anything resembling horror, thriller, or any coherent narrative, don't expect much from this delirious mess.