From literature it appears that the growth of a male or female plant from seed, except for the predisposition in the gender chromosomes, also depends on various environmental factors. For growers who are well experienced, percentage of female plants is 60% - 90% female, but less experienced growers can end up with 100% male plants. The environmental factors that, according to literature, influence gender are:
- a higher nitrogen concentration will give more females (at the three-pairs-of-leaves stage and continue for two or three weeks).
- a higher potassium concentration will give more males (at the three-pairs-of-leaves stage and continue for two or three weeks).
- a higher humidity will give more females (at the three-pairs-of-leaves stage and continue for two or three weeks).
- a lower temperature will give more females (at the three-pairs-of-leaves stage and continue for two or three weeks).
- more blue light will give more females (at the three-pairs-of-leaves stage and continue for two or three weeks).
- Fewer hours of light will give more females (at the three-pairs-of-leaves stage and continue for two or three weeks).
- In later stage, as you increase the light, the plants grow faster and show more females/less males. Sixteen hours of light per day seems to be the best combination, beyond this makes little or no appreciable difference in the plant quality.
- Another idea is to interrupt the night cycle with about one hour of light. This gives you more females.
- Spray dilute Fish Emulsion ( 1 tablespoon per gallon ). When the plants have three sets of true leaves, plus the top sprout, give them a wetting spray of Fish Emulsion. Do it once a day for three of four days. Top and bottom of the leaves.
- To achieve 100% female plants is to expose young seedlings for several hours to an atmosphere of Carbon Monoxide. It doesn't hurt the plants, but it could kill you.
- Treatment of hempseed with ethylene gas will increase the resulting number of female plants by about 50%. Ethylene is produced by certain plants (i.e., bananas, cucumbers and melons), and these can be used to treat hempseed in a simple manner. About two weeks before you plan to sprout the seeds, place them in a paper bag or envelope and put that in a plastic bag with the peels of a ripening banana or cucumber. Replace the peels after a couple of days, and change the bags to prevent mold.
- When hempseed is treated with the female hormone estrogen, percentage of females that are produced will increase by about 10%. Dissolve a birth control pill in water and soak the seeds overnight in the solution. After the initial soaking, continue to treat the seeds by sprouting them on a paper towel soaked in the solution.
