Male plants form small pollen sacs at the nodes
Female plants form white hair-like pistils at the nodes
Male sacs look round or oval and hang downward
Female pre-flowers look teardrop-shaped with two pistils
Male plants usually show sex earlier than females
Female plants develop tighter, more resinous flower sites
Male plants do not produce dense buds
Female plants produce buds if not pollinated
Check the nodes where branches meet the main stem
Use a magnifying glass for early pre-flower inspection