Only females produce THC, so we do not need the male plants. Even more they obstruct the growth of the female plants, because they fertilize them. So how do I see the difference between the males and the females ?
The female plant can be recognized by many features. A female weed plant looks healthy and has many ramifications. But the best way to find out if you are dealing with a male or a female is to look at the armpits of the leafs. The picture shown below is of a female, to be recognized by a hair coming out of the head.
What also helps to recognize a female is the beginning of flowering. A female plant will then show hairs everywhere at the ends of the ramifications. Where subsequently the tops will grow as you can see in the picture below.
The male plants can often soon be recognized for not looking really healthy. Moreover they only grow vertically so do not have many ramifications. The male plant neither looks that full and fat. The male weed plant often does not have that many leafs as a female plant does.