Nate & Nick Diaz: Invited to Spark It Up Like Real Rastas with Julian Marley!

UFC stars Nate and Nick Diaz are rank amateurs in the Octagon of ganja, according to no less an expert than Bob Marley's son ... who's offering to help the bros go pro, mon.

Turns out Julian Marley got wind -- herbal, we're sure -- of Nate and Nick's new line of bongs, and he tells TMZ Sports he's down to get high with them ... with a twist.

The reggae star says he's not one for bongs -- preferring to keep it old school with big, fat Jamaican stogies ... and wants to teach the Diaz bros to do the same, like real rastas do. Julian's strain of choice ... Lamb's Bread.

There's a problem, of course ... Nick already got a 5 year suspension for weed, and we're sure Nate's not looking to go down that road. Marley says, if nothing else ... he'd like to have them come chill at one of his concerts.