I've heard that too, and it is SOMETIMES true, but that's not a sure way to tell. I've had plants that I was sure would be male turn out to be a girl and vice versa. Once you start flowering you will know for sure.I thought I read some were that male plants show a diffrent still of growing, like they don't grow branchs ect.. this is my first real grow so I'm still learning. A few days from my first harvest and just want to make sure I have something to put under the HPS light lol