General slang term for any strain of cannabis that is sativa dominant and thus produces a strong head high versus a body stone. Headies effect the prefrontal cortex and will make you feel euphoria, uplifting, cerebral, and psychedelic. Headies are a rarity in the domestic marijuana market as they take much longer to grow. 12+ weeks of flowering, vs the 7+ weeks flowering for indica strains. Therefore headies are usually a novelty shared amongst growers as they are highly prized flowers for their unique effect on the head.
Examples of headies strains would include,
jack herer, haze, sour diesel, durban poison and many many more