Datura ingested - e.g. as seeds (total hardcore) or brew (somewhat milder) leads to a heavy high though. Not listed as a drug, because you very rarely want to try it again.
Starts kicking in good 4h after ingestion - which often leads people to OD as they feel no effects some 2-3h in and take more. Once it kicks in, the strong high lasts a good 2-3 days, with milder aftereffects up to a week.
It's strongly hallucinogenic and kills your ability to discern hallucinations from reality. And the trip quite often takes a turn for bad - scary, disgusting, sad - never mind you acting upon it, where reality and hallucinations blend, which may turn quite dangerous or harmful. Quite scary as you retain the ability to e.g. operate machinery, but completely lose the ability to discern 'this is a really bad idea' - or, say, take proactive stance in whichever global disaster has the high spawned in your mind. And this taking two days non-stop, there is no easy way out.
So, uh, watch out. As long as they smoke some, no harm, no foul. But if you start hearing of datura cookies, or such, better take two days off somewhere far and safe.