The heroine bud (or hero bud for a male user) is a delicate pinkish flower which provides addictive sensations of euphoria when worn in the hair. Prolonged use is apparently detrimental and certainly has bad effects on the user's signamancy.
Heroin buds are a form of applied Flower Power.
Real World References
An apparently obvious reference to the addictive real world drug heroin (clinical name diamorphine), which is also derived from botanical roots (specifically the opium poppy) - albeit with significant processing.