I am making feminized seeds using STS (silver thiosufate solution) and will show you how to make your own feminized seeds without spending a ton of money.
Here’s a video explaining the process of making fem seeds with STS solution:
Female Seeds Get A Bad Rap
First lets dispel the myth that feminized seeds are hermies or are hermie prone. If you use stable genetics and reverse a female to male the plant is no more hermie prone than a normal female plant.
But many “breeders” let their greed get the better of them and want to release the latest hot strain and so they self strains often without testing the genetics and often without testing the cross. Very often these crosses are unstable and even made with seeds from a high demand strain that hermied. No wonder fem seeds get a bad rap.
How Feminized Seeds Are Made
There are a number of ways to make feminized seeds. One method called rodelization allows plants to over mature and make seeds. Plants will often produce seeds without a male by making their own male flowers. It is a survival mechanism that works in the wild but not in the grow room. Plants that produce seeds with this method are naturally hermie prone.
Colloidal silver can be used to reverse plant sex. It must be sprayed every day until male flowers form and many people have used colloidal silver to reverse their plants. I am not going to cover this here as there is lots of info online about how to use it and even build a generator to make it.
STS or silver thiosufate solution is the preferred way to make fem seeds. It is what is used by professional cannabis breeders and in commercial horticulture in general.
Making STS Solution
Here is a link to a PDF that explains how to make STS https://phytotechlab.com/media/documents/TechnicalLiterature/PreparationOfSTSsolution.pdf It should be noted that this solution needs to be diluted further before spraying plants with it.
Also it uses silver nitrate and sodium thiosulfate already diluted to 0.1 M but dont worry if you are not a chemist because I have an easy way to do it. You can buy both ingredients from Amazon already properly diluted and it will cost only about $40 to buy it. With seeds going for $100 a pack and more and fem seeds often going for $10 each it is cheap.
Make Your Own Feminizing Spray
I started my seed project by buying a premixed spray off eBay. It may have gotten to old or may have been diluted too much but it did not work well.
After spraying pistils should be turning brown and drying up but most of mine were not. After using my homemade spay the sprayed buds were turning brown within less than 24 hours. So mix your own because the solution needs to be fresh.
You will need to mix the two in a 4:1 ratio always adding the silver nitrate to the sodium thiosulfate. You can use plastic to mix them although glass is better. Do not use metal containers anything metal to stir the 2 together.
After they were mixed they were poured into a pint spray bottle and I added some distilled water and a drop of dish soap to it.
Common recommendations are a 9:1 dilution rate but I found that some breeders use a 5:1 ratio and I decided to go with that.
Keep the silver nitrate and the finished spray solution in the dark. I store mine in the fridge. No special storage is needed for the sodium thiosulfate. They will keep for a long time and you should be able to carry out several breeding projects with them.
Just remember that the STS solution is only good for about a month and you will get your best results using it right after making it.
MAKING FEMINIZED SEEDS USING STS
You want to start spraying your plants about 4 days before moving them into 12/12 lighting. Some people just spray the buds or a selected branch and some spray the whole plant. However you do it you need to spray every 4 days until you start to see male flowers and then you can stop.
You will probably see white female pistils at first. They will turn brown and dry up from the spray and become male flowers usually in 2 or 3 weeks. Remember this plant is female so it is natural for it to start out with female flowers. Perhaps if I had started with a stronger and fresher spray in veg they would have been male to start with.
The silver interferes with ethylene production. Without ethylene the plant can not make female flowers. But because it is going to flower anyway it can only produce male flowers. So you are not producing a hermie plant. You are producing a female with male flowers and as a result anything she pollinates will make fem seeds.
Some Strains Are Harder To Reverse
It seems some strains are harder to reverse than others and my guess is the more stable the strain is the harder it is to reverse. The Black Banana I am trying to reverse seems to be one of these. That is why I chose to make a stronger solution and I have not seen any burning of foliage even at a 5:1 dilution rate.
Timing is everything?
I started everything into flowering at the same time. I assumed that the spray I used would work and that males flower sooner. But that did not happen this time. Normally my plants are flowering within 14 days of flipping them over. So it might be better to start your treated plant a week or two before the others.
I am hoping that pollen will fly before the other plants are done flowering. If it doesn’t I will have a bunch of bud to harvest. But I would expect to find some seeds in my target plant at least.
Do not try to smoke the treated plant. You need to throw it out.
Day 26 First Male Flowers
Been spraying STS regularly starting in veg about 4 days before switching them over to flowering. I have been checking for male flowers daily and have mainly focused on the top buds.
Today I decided to check the lower buds on this Black Banana plant. Guess what? I found some too! They are hard to see and harder to pick up on camera. But trust me, they are there. They will be more obvious in future updates.