STS Solution Feminizing

Has anyone here actually done the STS feminization process?

I have my silver nitrate and sodium thiosulfate.

There is an article on ILGM about it but doesn’t provide instructions on actually preparing the solution. I have found other articles online that deal with it and enough of them the same that I’m confident I have that process. But the ILGM article says to spray once, other articles say to spray every 5 days for varying amounts of time.

The plants I want to use are my own strain for the first round and they’ve just sprouted so I have a few weeks to gather information.

So, the question - Has anyone actually done this process themselves and can you provide some detail on how you did it?


Don’t know who else might be able to help.

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Breeding is not my forte’ I understand it but I haven’t had to do much more than hyper extend flower period to force hermi for seeds. To get seeds or force female to hermi is simple even without chemicals bring to flower then add stress once in full bloom turning light on for messed up duration during 12/12 like 12/6/2/4 or just leaving plant well past harvest window can trigger


Im not a breeder either
I grow from seed with a occasional clone or two
But i will be watching this thread

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Thanks guys. Hopefully someone who has done this trick will happen along. I’ll post my learning process here as I go. It looks like a simple enough trick.

Maybe some future pharmer will find it useful.

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I’ve used colloidal silver as well as some of the processes that @Donaldj explained… never heard of this process… maybe @Aquaponic_Dumme might have some info… :wink:

:v: :sunglasses:


OK, so I’m going to start posting pics and info to this thread as I gear up for this experiment. Specifics and details are hard to find online but I think I have enough to get started.

In a week or so my first plants should be ready to take some cuttings and flower them. I have 10 seedlings started in a temporary veg area I have set up:

Any thoughts, opinions or personal experiences will be appreciated.

Here’s the process I’ll be using. After a lot of reading around, the process at

seems to be the most complete rundown and is based on the writers personal (successful) experience. It also seems to agree in most aspects with other info available online.

Summarizing here and correcting some typos and incorrect info from original post for my benefit:

In essence, STS Solution Feminizing consists of spraying a known female plant to stress it into becoming male. The resulting pollen contains only female material. Next you pollinate your female plant and let it go to seed. The resulting seeds will all be females.

This process requires the preparation of 2 “parts” of the solution, then mixing the 2 parts together and diluting to create the actual Silver Thiosulfate Solution (STS) you will use to change the sex of your female to male.

No plants treated with STS Solution should be smoked, eaten or ingested in any way.

Part A: .5-gram silver nitrate stirred into 500ml distilled water

Part B: 3.9 grams sodium thiosulfate Pentahydrate stirred into 500ml distilled water

Stock Solution A

  • Fill a pyrex 2-cup measure to the 500ml line with distilled water
  • Measure .5 Grams of Silver Nitrate using a digital scale
  • Slowly pour the silver nitrate crystals in to the 500ml of distilled water while stirring
  • Stir until dissolved (15 seconds)
  • Pour the solution in to a 500ml brown glass bottle and cap it tightly
  • LABEL the bottle “STS PART A” in a clear and long lasting fashion
  • Thoroughly wash and rinse the pyrex measuring cup

Stock Solution B

  • Fill the pyrex 2-cup measure to the 500ml mark with distilled water
  • Measure 3.9 Grams of Sodium Thiosulfate Pentahydrate
  • Add the Sodium Thiosulfate to the distilled water while stirring
  • Stir until completely dissolved (30-45 seconds)
  • Pour the Sodium Thiosulfate solution in to a 500ml brown glass bottle
  • Cap it tightly
  • LABEL the bottle “STS PART B” in a clear and long lasting fashion
  • Thoroughly wash and rinse the pyrex measuring cup

Mixing and Diluting the Stock Solutions

Always Mix Part A in to Part B

This means putting part B in a container first and then adding part A while stirring. The measurements listed here make 16 ounces.

For 16 Ounces of Solution:

  • Use a 60cc syringe and suck up 25cc of Part B solution
  • Gently squirt the Part B solution in to the Pyrex measuring cup
  • Completely rinse the syringe or use a second clean syringe
  • Suck up 25cc of Part A Solution

While stirring the stock solution in the measuring cup rapidly (use a small Stainless Steel Whisk), gently squirt the 25cc’s of Part A solution in to the measuring cup. Go slowly, yet quickly enough to completely mix them within 30 seconds.

The mixture must now be diluted at a 1:9 ratio with distilled water for use. The 50ml from above (25ml each of parts A and B) would be mixed with 450ml of distilled water for 500ml of ready to use STS. This should actually make 17 ounces to fit into your 16 ounce spray bottle…Hmmm.

When stored in a dark cool place, the mixed solution is effective for approximately 1 month. The A and B solutions will be effective for at least 6 months.

The recommendation is to use a brown glass spray bottle as found on Amazon:

Spray plant away from other plants, let dry and return to under lights. Switch to 12/12. Spray every 5 days. After a few weeks you should have mature pollen sacks and can proceed to pollinate your females.

DISCLAIMER: This is my summary of information I have found online about this process and my attempt to create feminized seeds. YOUR use of this process is your sole responsibility and should not be attempted by you without verifying the accuracy, correctness, legality and safety for yourself.I leave this here strictly for the information and edification of future hobbyists.


Also, as an aside, I’m using Sodium Thiosulfate Pentahydrate.You can apparently also use Sodium Thiosulftate Anhydrous.The proportions will be slightly different but the result is the same.

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@PhantomFarmer I’ll be following along, too. My sts components should arrive tomorrow.

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Fantastic @Garyak it’ll be nice to compare notes.

My current crop of candidates. Within a few days, I’ll begin taking cuttings to flower.

We’re allowed unlimited seedlings and we have enough adults in the house that even if I flower them all at once I’m still in compliance with state law.


Yesterday I topped 9 of the 10 candidates and set them in peat pellets under 12/12. Culled 1 that was tacoing on me.

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OK, so I haven’t abandoned this. I had timing problems with selecting clones and needing my grow space for spring plants. I now have a few candidates, some Northern Light clones and a couple of my local strain. I’ll be updating this thread again in the coming days when I spray my first plants.

I’m going to spray a couple of clones to produce feminized pollen and take it carefully to the garden and pollinate a branch of an existing female out there. Then I’ll do a couple of the NL in pots in another area of the property.

The lesson I’ve learned so far is that taking a clone and immediately putting it under 12/12 didn’t work very well for me. They seemed more interested in making roots than flipping to flower. After about 3 or 4 weeks of 12/12 they were showing no sign of flower and I was running out of time. So, I scrapped it and moved on.


Yeah; there’s a point of diminishing returns between vegging the clone long enough to flower versus trying to do both. I think generally it’s best to let it get rooted before dropping the lights.

I’ll be interested in how this goes. @FloridaSon and @Bogleg and @MattyBear might like to see this. Tag me in?


Consider yourself tagged, @Myfriendis410 !

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I’m watching for sure! Thanks Alan for the tag :v:


Heck yeah! Now we’re cooking with gas!


This right here would keep me from using this method.

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This technique is used to sex cuttings. Usually the females are returned to veg lighting to build a proper root structure to feed the buds.

Experience teaches us the best! Lol…

Thanks for the tag, Brother!

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The same applies to Colloidal Silver. The only method I know of that wouldn’t effectively poison the plant is Rodelization (manipulate the light period to stress the plant). With any method, you’re creating a male plant anyway, that you wouldn’t be consuming.