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Pheno Hunting/Cause of Herming Plants

When sprouting new strains from seeds to pheno hunt, say for instance you purchase a 10pk of seeds and then sprout them out. On average how many usually turn out to be male, and how many of the potential females herm when they are put into bloom?

We are pheno-hunting with several strains and there were questions raised over whether how we are growing may be CAUSING our plants to herm. Some of our growers think that the amount of plants that are herming is too high.

I found an article, (Sex Change in Plants…), granted it’s from 1980, but it discusses what can cause a plant to grow male parts and it includes Cannabis in the study. Very interesting.



Generally I have found a 60-80% female ratio from seeds, some strains give higher rates of females. Hermaphroditic behaviour can also be stress related (heat, water stress etc) - but it is also can be a natural plant response to create seed and breed. In a general population of cannabis (remembering the majority of strains are now very inbred) there may be a hermaphoditic gene in 2.5-5% of plants, this may be increased again through environmental stresses.


Hi @anneface011389!

The herming from stress is actually not a far-fetched idea. In most of my evolutionary biology courses, we often stumbled upon the question of sex. It’s one of those things that is resource-intensive and needs a good reason to happen. The most common reason was pathogenic, to create a genetically diverse set of animals that could resist disease. However, environmental stress can play a big factor as well, because sexual reproduction also allows for advantageous genes to spread through a species much faster.

For plants and animals capable of asexual reproduction, they usually have a “feature” where they can switch between asexual and sexual reproduction. They typically reproduce sexually when they are under a significant amount of stress – be it environmental or pathogenic.

If your plants are herming, check to make sure they’re not being put in stressful conditions. Sometimes it can be something subtle, but plays a large role. If you can, check the roots and leaves for any signs of problems, including pests.


I wonder if our AquaM0n-LeafMon system, which measures stress ( crop water stress) 24/7, and gives you an ongoing CWSI- Crop Water Stress Index, would be useful in monitoring and controlling the stress at fairly precise levels. this has been used for a few years now with Almond, Walnut and Grape growers in California.
Check it out at and/or call me, Frank at 408 482 2822.


In my experience about one in ten seeds lately are strongly male. Definitely some hermaphrodites sprinkled in there every now and then, but I haven’t noticed any patterns on that.

@anneface011389 I’m sure you know about this (saw your creds on your page) but for others reading here’s a quick thing to consider with cannabis sexing. A monoecious plant always has one plant with both male and female reproductive organs. A dioecious plant has male only plants and female only plants. Cannabis is a perfect example of what is called a trioecious plant. This means one plant can exhibit any of three sexual traits at any given point based upon environmental stresses: male, female, or both male/female. Any cannabis plant, no matter how feminized, can at some point develop stamen. Breeding is also about removing as much male potential as possible but with a trioecious plant this isn’t possible, at least in a non-GMO style. I’m sure there is a way to do this with more research on cannabis genetics in particular, but removing portions of the chromosomes that make cannabis male could also disrupt other very basic things such as metabolism or protein formation.

I’d say to try and grow your seeds in the conditions you would use in day to day operations. Trait hunting is also about finding out which plants do well in your production environment. It doesn’t really matter if you have the best strain in the area if it is killing your crew and equipment to produce it. If you have another operation in a different region I would take your clones there as well and look for differences in sex. You can even swap strains with a trusted grower in a different region and do the same experiment for them, doubling your hunting capacity as long as you both get to keep cuttings. There’s a slew of things that can make cannabis transition between sexes. As long as you are capable of producing great flowers I wouldn’t get too hung up on the amount of male flowers appearing.