Sexing Cannabis: A three-part series from cannabis physiology and physical differences between sexual organs, to tips for sorting genders that works best for your medicinal garden.
PART III: Tips for sorting genders: which method works best for your medicinal garden
Thank you for tuning back in to our final segment of the three-part series on Sexing Cannabis! Now that you’ve learned the basics in cannabis physiology and have taken a closer look at the physical differences between male and female sex organs, we can now explore different methods to help speed up the process of sexing plants in your medicinal garden. Any farmer that is not intentionally breeding will tell you that a pollinated female cannabis plant is deficient in medicinal properties—thus the shorter time it takes to identify a sex the better your chances are of preventing pollination from occurring. With that in mind, let’s look at some possible methods that are available.
Allowing nature to take course:
If you choose this farming method, there will be a point in time when your plant will start to reveal its gender without any interference on your part. At this stage you can determine which male plants to cull from your crop to keep them from pollinating any ladies. Now, while it is true that this method requires no additional effort (other than keeping a keen eye on the growing ladies) and does little to interfere with or manipulate the natural growth cycles of the plant, it does in fact present a few drawbacks. With the philosophy that time is money, and that nutrients are not cheap, time wasted caring for unwanted male plants is money wasted in nutrients, space, and energy (or TLC depending on how a farmer looks at it). You must also consider the fact that different strains will begin flowering at different time frames depending on the amount of sativa or indica in the breed.
Growing outdoors: under natural sunlight most hybrids will reveal their sex and begin to flower around August 1st.
Indica strains are adjusted to the natural light cycles of the northern parts of the world and will usually begin flowering when exposed to 8 – 10 hours of darkness. In California this means possibly sexing and flowering as early as late June.
Sativas developed nearer the equator require longer dark periods to begin flowering. Some sativas will continue vegetative growth until they are exposed to a full 12:12 hrs of darkness. Being outdoor and depending on natural light means some sativas in the Northern Hemisphere may not begin flowering until late September.
Manipulating light cycles
At any stage of vegetative growth cannabis plants can be forced to reveal their sex through successful manipulation of light cycles. Expose the plants to a longer night cycle, from either 24:0 or 18:6, to 12:12 and you can plan on seeing either “balls” or “hairs” within about a week. After a week the light cycle should be adjusted back to 24:0 or 18:6 so the plants will return to vegetative growth. While this method shortens the time it takes to sex a plant, it doesn’t always work. Some male cannabis plants originating in far northern areas are not photosensitive. This means you can not trigger flowering by manipulating the light cycle because it is age and the naturally occurring developmental stages of the plant that determines when the male displays sex and begins to flower. Also, some indica dominant plants don’t always want to return to the vegetative phase and can produce some bizarre and unwanted growths or even carry on into full bloom prematurely.
Clone and sex
In my personal opinion, the most effective method for determining plant sex is to take clones from each plant, root the cuttings, flower them and then sex the mothers/fathers based on the sexual reproductive organs revealed in the flowering clones. You can then discard the male plants unless you intend to breed, as they only pose an imminent threat to the prospering ladies. This method allows you to know the sex of each plant in as little as two weeks without having to manipulate the light cycle of the original seeded plant, but while this could work for smaller crops it can be difficult to manage with bigger grow operations; imagine having to take 1 or 2 clones from individuals in a forest housing up to 99 plants!
Using blue lighting
Cannabis is a short-day plant, meaning that as the days get shorter it determines when to flower based on the number of uninterrupted hours in darkness. The method by which cannabis determines and measures the length of a dark period is by using the hormone phytochrome which can be found in 2 states:
- Inactive state ( Pfr): occurring when it absorbs red light spectrum at 666 nanometers
- Active state (Pr ): triggered i in as little as 2hrs of being exposed to complete darkness.
When high levels of flowering hormone (Pr) remain elevated over a critical period of time for several days, the plant will start to transition from vegetative growth to flower. The hours of darkness required to begin flower differs greatly by the different species of cannabis plants. Sativas, because they develop near the equator, require a longer period of darkness than indicas and some sativas will even continue vegetative growth in 10-11hrs of darkness which would otherwise cue most plants to flower. The active form (Pf) can be returned to its inactive state, stopping the flowering response, with interruption by red light around 660 nm or even blue light; when Blue LED or fluorescent light is the only light used on an 18:6 light cycle, the plants will slightly begin flowering while simultaneously continuing vegetative growth. After sexing they can be returned to a full spectrum light at 18:6 to produce more a robust vegetative growth and halt the flowering process. This method works well for higher populated cannabis gardens that would make using the clone and sex method a bit tricky.
So, now that we’ve discussed how pre-flowering male and female cannabis plants develop and the imminent dangers posed if a male’s presence is allowed to go unnoticed in a garden, let us return to the reason why we wish to protect any prospering lady from pollination. Sensimilla girls (female cannabis plants that go un-pollinated) will mature to produce prolific amounts of flowers abundant in Delta 9 Tetrahydrocannabinol (THC). When attempting to cultivate the pain-relieving and healing properties of THC for medical use it is of the utmost importance to be able to sex your garden early and effectively. A pollinated girl will focus mainly on continuing her genetic lineage as opposed to an un-pollinated girl who can focus solely on creating quality medicine for patients in dire need of it.
I hope this series has been helpful to the farmers out there and that the next time you need to sex a cannabis plant in your medicinal garden— you can do so confidentially and without hesitation.