Did it go something like this?
The environmental factors that influence the sex of the cannabis plant (or the flower in the case of hermaphrodites), are among other things:
The quantity of nitrogen and potassium of the seedbed. Humidity and moistness of the seedbed.
Level of temperatures.
Colour of the light used.
Length of daylight.
Stress, any form of stress, makes that more male individuals will originate from seed. Even the taking of cuttings from female cannabis plants may produce male or hermaphrodite cuttings.
To optimize the result, changes in one or more of the above-mentioned environmental factors for a certain period during marijuana growth, may be applied. During this time these environmental factors will deviate from the standard growing system for maximum harvest and quality, as described in nursery literature. The desired change(s) in the environmental factor(s) are started from the moment that the marijuana seedling has three pairs of real leaves (not counting the seed-lobes). This is the moment that male and/or female predisposition in florescence is being formed. After approximately two weeks the standard growing system can be reconverted to.
Of the 5 above-mentioned environmental factors the first three are the most practical:
- Level of nitrogen and potassium of the seedbed: A heightening of the standard level of nitrogen makes for more female cannabis plants originating from the weed seeds. A lowering of the nitrogen level shows more male cannabis plants. A heightening of the level of potassium tends to show more male marijuana plants, while a lowering of the potassium level shows more female marijuana plants. A combination of a higher nitrogen level for the period of a week or two and a lowering of the potassium level is recommended.
- Humidity and moistness of the seedbed: a higher humidity makes for an increase in the number of female cannabis plants from weed seed, a lowering for an increase in male cannabis plants. The same is valid for the moistness of the seedbed.
- Level of temperatures: lower temperatures make for a larger number of female marijuana plants, higher temperatures for more male marijuana plants.
- Color of light: more blue light makes for female cannabis plants from seed, more red light makes for more male cannabis plants.
- Hours of daylight: few hours of daylight (e.g. 14 hours) makes for more female individuals, a long day (e.g. 18 hours) makes for more male cannabis plants.
Now let me just make a few adjustments here to this. You can do whatever you want to your cannabis plants in seedling stage and early vegetative stage of growth and it will not effect your final male to female ratios. The time when things should be near perfect is in or around the 3rd to 4th week of vegetative growth.
This is the CRITICAL TIME for getting those female ratios up and up. I realized this clearly when noticing how some cannabis plants hermed because of problems that occurred around this period of the cannabis plants development. If the problems occurred before this time - no herms. So for this reason I surmised that this is when the crucial gender selection is made by the marijuana plant.
Now I believe that the genders are set in the weed seed however the environment has a massive impact on how this is expressed in the final phenotypic expression of the cannabis plants gender. There are probably many genes that govern this, however lets get into how to up these female ratios.
The Italian Society of Agricultural Genetics agrees the sexual differentiation of cannabis is strongly influenced by environmental factors such as temperature and photoperiod. Anomalies also occur in floral development like the presence of reproductive structures of the opposite sex, or the development of bisexual inflorescences (monoecious phenotype).
At the 3rd to 4th week of vegetative growth make sure that your marijuana plants are free from stress. No pests attacks, no fungi attacks, no mold, no irregular photoperiod, not underwatered, not overwatered, not pruned or topped, a cannabis friendly soil mix, not recently transplanted, no small pots. If have these basic growing conditions under control then we can move onto the real forces of female production from standard weed seeds.
N
:K and nutrients. What this simply boils down to is that you have the right nutrients present in the right ratios. A nutrient formulation that has roughly equal parts N, P and K is great but if the P levels go up or the N levels go down you are starting to look at a flowering type food for cannabis. If you do this then your odds of producing mostly females is greatly decreased. Make sure that you get those N, P and K levels to almost run from higher to lower amounts from N to P and K.
I have noticed that equal portions of N to P an K can help with the female ratios but the higher N is certainly more helpful. So around the 3rd of 4th week of growth make sure that the ratios are good and that P or K has not gone above the N and P or else more males will occur. Obviously this means to avoid overfeeding your cannabis plants around this time too.
Never let your medium dry out completely around the 3rd to 4th week of vegetative marijuana growth. If you make sure to water occasionally, but not to overwater your cannabis plants, you will get those female ratios on the up and up. Overwatering or drying out of the medium will only produce more males. For consistent results in getting more females keeps those mediums moist.
Humidity. Now this is the tricky one. High humidity levels only promote fungi and mold development and lowering humidity levels is the way to cure most of this rot but by keeping those humidity levels up in or around the 70 rH factor will help to produce more females. If you have a low humidity grow room then you should get to hold of a humidifier. Now high humidity levels like 70rH cause the medium to dry out a lot quicker so you got to keep this under control too. Keep those mediums moist and those rH levesl at 70. This will help to improve those female to male ratios. Again, getting them on the up and up.
If you run the 24/0 photoperiod then do not allow those temps to go anywhere above 85F unless you have an equatorial strain. 75F is the best but going a little lower is not a problem for helping those female ratios. If you can get in at around 65F then those females are going to be popping up all over the place. The problem with this is that some growers like to use the 18/6 photoperiod and when the lights are off the temps drop from around 65F to 50F and even less. Try not to be below 55F because this has the adverse effect on the plants producing more males than females. Again between 65F and 75F is where you want to be during the 3rd to 4th week of vegetative growth, the preference being 70F.
Invest in a MH Light for vegetative growth. Dump the HPS bulb for flowering later. I have noticed that HPS lighting during vegetative growth simply sends those males to female ratios all over the place. With MH lamps the females are everywhere. Invest in some MH HID lights. It makes all the difference in getting those females to show more often. This is worth repeating! MH Bulbs produce more females under optimal conditions especially if they are present during the 3rd and 4th week of vegetative growth. Surprising enough you can start seedlings under HPS and it will not have an effect on those female ratios. Again the 3rd to 4th week of vegetative growth is what is important here.
No stress during the 3rd to 4th week of vegetative growth. That is all there is to it. If you got your garden growing in optimal conditions without marijuana plant stress then the impressive 90% to 95% females start to emerge from standard cannabis seed packs. I find that topping is best done at the second to third week of vegetative growth but that this is a little stressful and can lead to those female ratios dropping again. Avoid topping or pruning if you are looking to up the female count.
