Mess with the light cycle. I first noticed it worked when I had a power outage that threw my timers off. I looked all of my plants over with great care at all stages of growth. I grew single cola plants that finished at about a foot. Male flowers after they open turn yellow and ae easily notice. I had some seeds yet no male flowers. Other professinal growers concured that fluxuation of the light cycle (dark releases hormones) will cause stress seeds with no male flowers. Every seed I ever hatched from these seeds has been female. I have produced over 1000 female seeds.

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