|What's the Difference you ask?
Males are often, but not always, tall with stout stems , sporadic branching and few leaves. Males are usually harvested except those used for breeding, after their sex has been determined, but before the pollen is shed. When harvesting, especially if close to females, cut the Marijuana plant off at the base, taking care to shake the male as little as possible. This helps prevent any accidental pollination by an unnoticed, open male flower.
When a male enters the stage of flower development, the tips of the branches where a bud would develop will start to grow what looks like a little bud (little balls) but it will have no white hairs coming out of it. Females will have no balls and will have small white hairs.
Cannabis in temperate climates begin to show his sexual identity by the end of July (end of January in the southern hemisphere) in different dates according to the varieties, Marijuana being the resinous flower of female cannabis plants intended for seed production, in absence of pollen buds turns out pure sensimilla weed and is gentle and sweet to smoke.
It is very important to get rid of male plants on time, as they are unwanted pollen carriers. By the early flowering stage male cannabis, if compared to female's, shows quite a different structure but the characteristic excrescencies would be the sex indicator this are called primordia and will emerge by the side of the third or fourth internodes in the main stem.
Female cannabis are completely revealed when the characteristic "V" shaped pistils become visible, all this to a close observation. Outdoors males will uncover themselvesapproximately three weeks before the females, indoors sexing of both males and females happens within a week to ten days according to the variety.
We've heard of urban legends about environmental conditions, age of seeds, added chemicals and even lunar stages having an influence on sexual differentiation of Cannabis; you might take note of those suggestions as personal communications, but a good handbook or an internet surf works the best if you lack in experience when sexing.