Seed Feminization


Dear BluntMBA – “Seed sellers often talk about feminized seeds. I understand that I want female plants, but how do sellers make feminized seeds?” 

 – Curious in San Diego, California

Dear Curious,

As you are aware, cannabis is a dioecious plant—male and female plants are separate. In the wild, male and female plants will grow side by side. In the fall, when the plants start to get stressed by less light, the females will flower and the males will produce pollen. The wind carries the pollen from the males to the females, which mixes their DNA and creates seeds.

Seeds are undesirable in a marijuana crop. They are both annoying to the end user and represent energy that the plant could have put into growing larger and more THC-rich flowers. To avoid this problem, seed producers take advantage of cannabis’ ability to become a hermaphrodite. A female plant that undergoes significant stress will produce male parts and pollen. Pollen can be carried by the wind (or just the air circulation in your grow room) to a female plant, producing seeds. Because both plants involved in this reproduction are female, they do not contain the chromosomes to be male from sprouting. The seeds are very likely to be female—so they are called “feminized.”


Dear BluntMBA – “I’ve heard of “rodelized” seeds. What are they?”

–  Rodelwhat from Oakland, California

Dear Rodelwhat,

Rodelized seeds are feminized seeds that, like all feminized seeds, are produced with the pollen from a hermaphroditic female and the pistillate flower from a regular female plant. In mass seed production, there are two popular techniques to force flowers to be hermaphroditic.

The first technique is where growers spray the plant with a chemical. Colloidal silver is one popular agent; sodium thiosulfate mixed with silver nitrate is another. These agents, when sprayed on the plants, cause a severe stress reaction. When unfertilized female cannabis plants undergo stress, they become hermaphrodites.
The second technique is where growers let plants continue flowering well past the normal harvest date. Female cannabis plants that have reached full flowering maturity without being fertilized begin to undergo significant stress and become hermaphrodites. This technique is called rodelization.

The first strategy is significantly faster and therefore cheaper. Most feminized seeds are produced this way. It is not organic, however. Growers who would like to keep their product natural prefer rodelized seeds because no unusual chemicals ever need to touch the plant.


Dear BluntMBA – “I have had “feminized” seeds turn out to be male and ruin an entire crop before.  How soon can I tell if a plant is male?” 

– Nervous in Boulder, Colorado

Dear Nervous,

I’m sorry to hear about your crop! While most feminized seed producers are quite effective, some do have issues that cause the production of males. Considering the extreme cost of accidentally finding a male in your cultivation, it is important to be wary.

With advances in technology, you can actually tell if a plant is male within days of sprouting. There are DNA testing companies that will use a rubbing from your seedling to check for male chromosomes. They can do this as soon as the third leaf shows, and the test only takes a couple of days. This will identify true males, but if you have a plant that shows easily hermaphrodites, you can still accidentally pollinate a room.

If you want to go the low-tech route, some growers recommend running a 12/12 light schedule for a week or otherwise stressing a young vegetative plant to induce pre-flowering. With vigilance, a grower can identify the sex differences between the male and female plants as soon as the pre-flowers begin to show (the male flower looks like a banana). After the plants have revealed their sex, remove the males and remove the stress on the females. They’ll go back to vegetative growth and you can continue happily.

I would advise against this approach. Any stress that your plants experience represents energy that is not going towards ideal growth, and energy is money. Use a reliable vendor, be extremely vigilant when you begin the flowering cycle, and you should be okay. Catch those males early!

Dean Croshere is a California-based writer, speaker, and advocate for marijuana growers. His experiences in cultivation, extraction, and food and infused product production began in the early days at MedMen, where he was instrumental in designing new facilities for each stage of production and applying relevant procedures across the country. He holds an MBA from the University of Southern California (USC) and currently leads Business Development for Link4 Greenhouse Controls (, advising on product development and new business ventures.


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