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Tutorial DIY STS Mixing/Using Guide for Feminized Pollen/Seeds R.C.Clarke Method as Base

Douglas.Curtis

Autistic Diplomat in Training
Feminized Seeds are Awesome
Hermaphrodite plants are not awesome. Fortunately, it's possible to create cleanly produced feminized pollen. This pollen can be used to create seeds which are 99.9% female. As long as logical safeguards are taken, these seeds will not be any more sensitive to becoming hermaphrodite than the parent plants

This particular recipe for STS was originally published by Robert C. Clark. Today it is arguably the most recommended and successfully used method of feminizing cannabis. This write up includes the original recipe, along with practical useage tips and other helpful information gained through research and experience.

I know you'll be greatly pleased with your results.
Early-Dane-Spitting-Pollen-1024.png


Non-Hermaphrodite Plants Begin With the Parents
Stress testing your female plants is essential to removing breeding plants with hermaphroditic tendencies. Even if you're **not** using feminized pollen, breeding with unstable parents can produce hermaphroditic seeds. It's extremely important to expose your potential parents to the stresses most commonly known to trigger hermaphroditic flower production. These include, but are not limited to, the following stresses:
* Inconsistent Light Schedules
* Pinhole Light Leaks During Flowering
* Excess or Extreme Changes in Temperature
* Bound Roots
* pH too Low/High
* Lighting Spectrum Change
* Media Excessively Wet/Dry
* Excessive Supercropping/Heavy-Trimming
* Root Pruning
* Proximity to Sessions (just making sure you're reading. lol)
* Over/Under Feeding
* Incorrect Nutrient Profile
* Insects/Disease/Fungi
* Pesticide/Chemical Exposure
* Extended Flowering Time

Only the females which stay 100% female through the tests should be used for breeding purposes.

Yes, Stress Testing
Choosing excellent parents can take a long time and consume a lot of resources. These factors are the main reason so many unstable seeds are available today (2018), Patience and persistence pays off here. The more stable the genetics you're working with, the quicker you'll have a large enough number of potential parents. Each stress takes 1-3 weeks to form male flowers. Stressing multiple clones, of the same plant, ensures accuracy of the test results.

The more stable the original female plants, the more valuable the end seeds will be. Keep stressing until you're absolutely sure the plant is stable. Again, be prepared for this process to take quite a while. Every extra ounce of effort you put into this portion of the program will pay you back in greatly increased quality. **You can do it!**

Silver Thiosulfate Solution (STS)

STS is the most commonly used chemical mix for creating stable feminized pollen. While it may not be the only method, it is arguably the most commonly used and is very reliable. Female cannabis plants require ethylene production to form female flowers. Without ethylene being produced, the female cannabis plant will produce male flowers full of feminized pollen. Silver Thiosulfate Solution(STS) suppresses ethylene production in plants. When this solution is properly applied to the bud sites of a cannabis plant, the plant will not produce ethylene. Again, without the ethylene, male flowers form.


The Basics of Making Silver Thiosulfate Solution
Can you mix a powdered drink mix? Congratulations! You have the skills to make Silver Thiosulfate Solution. STS is mixed up in two parts called "stock" solutions. These solutions are labeled A and B. Solution A is a mixture of silver nitrate and distilled water. Solution B is a mixture of sodium thiosulfate and distilled water. These two solutions can be kept in light-proof bottles, sealed and refrigerated, for extended periods of time, even years.
Chems-n-bottles-n-sprayer-small.png


Once solutions A and B are mixed together, the resulting mix is diluted with distilled water before using. Once mixed, the STS (both full strength and diluted) must be kept from light, and can be used up to a month when stored properly. I've used mixed and diluted solution which was kept in my refrigerator for over 9 months, but fresh solution definitely works the best.

Tools and Materials You Will Need
Where possible, I have linked the exact items I purchased and used. The remaining items I had around the house. 500g of Sodium thiosulfate anhydrous is a LOT of thiosulfate, so smaller projects may want to use the pentahydrate verion, because it's available in smaller sizes.
* Silver Nitrate
* Sodium Thiosulfate (Anhydrus or Pentahydrate Both Work)
* Distilled or Reverse Osmosis Water
* A Digital Scale Accurate to 0.1g
* Two (2) 32oz Brown Glass Bottles
* 1 32oz Brown Glass Bottle w/Black Sprayer Top
* 33 Gallon Black Trash Bag
* Tape
* 60 cc/ml Syringe
* Surfactant (Yucca-Extract works great)
* A Cool Dark Place for Storage (Fridge)
* Nitrile Gloves
* 500ml/2 Cup Glass Mixing Container
* Small wire whisk
* Safety Goggles

Basic Safety Recommendations
The following steps require careful measuring, along with basic chemical safety. It is strongly recommended you work on a flat surface with a plastic sheet or several layers of newspaper to protect it. Silver nitrate does stain brown to black, so gloves and safety goggles are recommended.

Sodium thiosulfate has a very low toxicity, make sure you still wash up any spills well to remove all concern. Both of these solutions can be safely rinsed down the drain, when followed by a large amount of water.

Measuring and Mixing Stock Solution "A"
* Fill your 500ml measuring cup with 500ml of distilled water
* Measure out .5g of Silver Nitrate
* Mix the silver nitrate powder into the 500ml of distilled water
* Pour the silver nitrate solution into a brown glass bottle and seal tightly
* Label the bottle "A" Silver Nitrate
* Thoroughly clean the 500ml container and rinse with distilled water

Measuring and Mixing Stock Solution "B"
* Fill the 500ml container with 500ml of distilled water
* Measure out 2.5 grams of sodium thiosulfate **anhydrous**, **OR** 3.9g of sodium thiosulfate **pentahydrate**
* Mix the sodium thiosulfate with the 500ml of distilled water
* Pour the sodium thiosulfate solution into a brown glass bottle and seal it tightly
* Label the bottle "B" Sodium Thiosulfate
* Thoroughly clean the 500ml container and rinse with distilled water

Keep Both "A" and "B" Solutions Cool and Dark!

Mixing and Diluting STS
The next step is to mix the two stock solutions together properly, creating the actual Silver Thiosulfate Solution (STS).

Before using the STS, it must be diluted to a weak solution for spraying! (Edit 8/2022: Best results are being obtained with Full Strength solution and 2 sprays. One on first day of flower, and the second at day 14. Long flowering may require a spray on day 28)

* Measure 50ml of stock solution "B" with the 60cc syringe and gently squirt it in the 500ml glass measure
* Thoroughly rinse the syringe with distilled water, or change to a new syringe
* Measure 50ml of stock solution "A" with the 60cc syringe
* While whisking solution "B" in the glass measure, slowly squirt solution "A" into the glass measure in less than 30 seconds
* Pour the mixed solution into the 32oz brown glass bottle with black sprayer top
* Add 900ml of distilled water to fill the sprayer the rest of the way, leaving room for a little bit of surfactant
* Add yucca extract in small amounts and shake well
* Test spray on a leaf to if solution still beads up and rolls off
* Add additional yucca extract and shake well, until the solution spreads across the leaf instead of beading up
* Thoroughly rinse all tools using more rinse water than usual


You now have a sprayer bottle with a 1:9 dilution of STS and water. **You want to do your best to protect it from light and heat**. Personally, I wrap the bottle section with a black plastic trash bag and tape it in place. This is for additional light protection while it stores in my fridge. (Edit 4/2020): I've kept the original stock solutions from this tutorial for 2 years now, on the second to bottom rack of the door of my fridge. I haven't changed a thing, and they're still in the same brown bottles you see in the photos. I mixed some fresh solution a few weeks ago for some projects and began spraying a stunted female autoflower with it. (why not, right? lol) Today I noticed a couple open nanners, so you can rest assured the stock solutions do not go 'bad' very quickly.
Chems-n-bottles-n-sprayer-med.png



Successfully Using STS!
I've spent a great deal of time researching the best method(s) to use for success with STS. First I'm going to detail the steps I've used successfully myself. I'm also including the thoughts and tips I've picked up from other growers. Cannabis is a nearly infinitely variable plant, so it's best if you have information from as many sources as possible. Who knows which tip will specifically fit your plants and setup. ;)

Regardless of the spraying schedule you use, **be sure to thoroughly saturate the branch(es) and beginning flower clusters**.

Spraying Schedule I've Used Successfully
* Spray branch(es) you want reversed 5 days before flipping to flower
* Spray every 5 days until major male flower formation has begun

Alternative Spraying Schedule A
* Spray branch(es) you want reversed 2 weeks before flower
* Spray branch(es) you want reversed on the day you flip to flower

Alternative Spraying Schedule B
* Spray branch(es) you want reversed on the day you flip to flower

(Edit 8/2022: As mentioned above, use full strength solution and spray twice. Once on first day of flower and once on day 14. Long flowering may require a spray on day 28.)

A Note on STS "Burning" the Plant
Many growers have reported the STS solution 'burning' the plant. I strongly recommend diluting your spray further than 1:9, if you experience any burning of your plants.
(Edot 8/2022: I believe the burning may be caused by unclean water or chemicals or soap, since I have never seen any burning except with 2yr old solution)

Additional Tips and Tricks
As always, the more information you have, the better you can potentially achieve. The following are little things which can make a big difference in your results.


Using Clones
When possible, I've found it immensely helpful to work with clones of the same plant, reversing one or more for pollen in a small flowering area first. The pollen is collected and stored. At this point, the pollen can be used on any female plants, including clones of itself.

Though it does involve a second step of collecting and preserving the pollen until use, it allows you to create seeds without dealing with a reversed plant in the room. An additional up side is the ability to store the pollen for years, when preserved properly.


Pollen Control
I STRONGLY recommend using filtered intakes and outtakes on any flowering environment you're creating or using pollen in. Many growers have reported developing allergies to cannabis pollen, after working with it for years on end. Filtering the air going in and out of your flowering rooms keeps pollen contained. (mostly lol)

I use spray bottles of r/o filtered water and spray down the air in the room, any time I disturb pollen. Knock the pollen out of the air after every session of working with pollen. Be sure to spray down the insides of tents and flower rooms after each run. This will minimize cross contamination from different pollen sources.

Diluting Your Pollen
Any visible bit of pollen you can see is made up of millions of bits of pollen, making one pollen per pistil pollination impossible. Mixing your pollen at one part pollen to 50 parts corn starch or flour prevents waste. Each pistil requires only one bit of pollen to create a seed and the dilution makes this easy.
(Edit 8/2022: This is best done when you actually go to use it. Dilution before freezing I no longer recommend.)


Using a Makeup Brush to Pollinate With
Many growers report excellent results with evenly pollinating plants, when they use a clean makeup brush. The brush allows easy application of the pollen evenly across the plant. When the pollen is diluted with flour, you're easily able to see which flowers you've already pollinated.
### Storing Your Pollen for Years (Possibly 10+ Years)
Pollen can be stored for a long time in a freezer, as long as it has been thoroughly dried. Silica packs do not absorb down to a low enough relative humidity, so dried rice is used.

Heat an open quart jar of un-cooked rice at 150F-170F for at least 12hrs (anyone know if you can shorten this?). Seal the jar with a lid and ring, and let it cool to room temperature. A wide mouth quart jar is significantly easier to open than a peanut butter jar. The vacuum seal formed while cooling down can be awful. lol

Collect your pollen and carefully transfer it to a foil baking cup or other small container which fits in the jar. Place the foil cup on top of the rice and seal the pollen in the rice container. Set the jar in a cool, dark place for 7 days. Cold temperatures will slow the drying.

(Optional: Toast some flour in a skillet on the stove until it is a dark tan color, then seal hot in another glass, airtight container and let cool to room temperature. This will remove the moisture from the flour. Remove the pollen from the dried rice jar and mix it at a ratio of 1 part pollen to 50 parts flour.) Pollen which has been properly dried does not need flour/cornstarch/rice-grains during storage. You can safely leave the option of 'dilution' till the time you actually use the pollen. I've personally switched to storing pure pollen, since who knows what the future will bring.

Seal the mixed pollen in small containers, foil or plastic sealed pouches or (preferred) 1.5ml centrifuge tubes.

LABEL your containers carefully, using the specific plant name, date and any other information you believe you'll remember later. (Because there's a good chance you won't)

Seal the containers in a thermos and keep it in your freezer. The thermos acts as an additional thermal protection barrier, just in case you have a freezer issue years down the line. It also makes transferring pollen from one place to another a safe operation. Just be sure to keep the thermos at freezing temps, and to limit the amount of time outside the freezer.

Stubborn Female Refusing to Turn?
While the most stable female plants are the type of plants we strongly want to breed with, they are often difficult to get quality amounts of pollen from. These tips should help even the most stubborn female in your stable flip large amounts of viable pollen.

Test Different Spray Schedules
Flower out small clones of the plant you want to reverse. Use a different spray schedule with each clone, keeping careful track. You may find one schedule works much better than the others.

Use Colloidal Silver
Some growers have reported success with the alternative spray schedules, with a follow up spraying of a high ppm colloidal silver solution, 2-3 weeks into flower.


Collect, Dry and Crush the Pods
Have a plant growing great big clusters of male flowers which don't seem to open, or don't have much pollen when they do open?

When the pods have swelled and look like they are fully mature and should be opening (they will look like fat footballs with stripes where the sepals are beginning to split apart), Cut branches and hang them to dry over a collection table until crispy. It should only take a few days. When the relative humidity (RH) is too high for hang drying, using the rice desiccant can get it done.

Drying Pods with Rice:
Strip the clusters of pods from the flowers, leaving as much leaf and stem behind as possible. Wrap the clusters in paper towels and bury them in a sealed jar of dried rice. (Heat un-cooked rice in an oven at 150-170F for at least 12hrs and cool in a sealed jar) The rice will absorb the moisture from the pods and dry them completely. Depending on the volume of the pods you're drying, you may need to stir them once or twice a day. This keeps them from rotting or sprouting fungi before they're dry enough. You should be checking/stirring often enough, you'll definitely be able to tell when they're dry enough for screening.

When the pods are completely dry and crispy, gently crush them through a tea strainer, or similar fine mesh strainer. You'll find large quantities of viable pollen.



What are you waiting for? Go make some fems!! :D
 
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Douglas.Curtis

Autistic Diplomat in Training
Hey thanks :) Glad you approve.


I'm looking forward to many, MANY decent feminized strains being available in a few years. :)
 

frostqueen

Active member
"This particular recipe for STS was originally published by Robert C. Clark."

wut

Nice write-up. This is actually Country Mon's original STS formula from 2003, not 'Clarke's method'. 1:5 thiosulfate to silver ratio, dilution rate of 1:9 or less, pre-stressing the plants to find non-herms, etc. etc. It was first posted on Cannabis World over 15 years ago.

But isn't that just the cannabis business world in a nutshell now, lol. So many unknown and uncredited soldiers in the history of this game. CM did a year of tests and research to come up with this. I do have a great deal of respect for Mr. Clarke, but sorry. Not his technique.

Regardless, this post is a great re-write of it. Nice job.
 

Douglas.Curtis

Autistic Diplomat in Training
I was under the impression Clarke published this in '81, definitely pre-dating Country Mon's posts.
(Edit: Correction, Marijuana Botany in 1993 which still predates by a few years)

Appreciate the accolades, I did take time to pull as much new data as possible while adding my own personal experience. :)
Thanks!
 
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Ibechillin

Masochist Educator
Great post, thanks for sharing DC. You mentioned colloidal silver but not how its made, this picture may be helpful also.

how-to-make-colloidal-silver-generator-to-make-feminized-cannabis-seeds.jpg


This is actually Country Mon's original STS formula from 2003

I was under the impression Clarke published this in '81, definitely pre-dating Country Mon's posts.

This made me lol.
 
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Douglas.Curtis

Autistic Diplomat in Training
Thanks CVH, I agree it's clear and detailed enough for it, definitely up to the mods though.

Excellent suggestion Ibechillin, though I would caution to be sure silver wire is .999 pure since most jewelry wire is not. ;) Easy enough to make, as you show, and there are several high quality suppliers on the net as well. :)
 
Great thread! Played around a little with STS in the past. Quite impressing when a plant you thought you knew well after growing it multiple times turns into a male. While the plant was packed with male flowers I had no luck collecting pollen though, all the pollen sacks were empty. So some genetics do seem to be harder to feminize indeed. Will try your tips about different spray schedules and combining STS with colloidal silver next time, Douglas!
 

djonkoman

Active member
Veteran
Great thread! Played around a little with STS in the past. Quite impressing when a plant you thought you knew well after growing it multiple times turns into a male. While the plant was packed with male flowers I had no luck collecting pollen though, all the pollen sacks were empty. So some genetics do seem to be harder to feminize indeed. Will try your tips about different spray schedules and combining STS with colloidal silver next time, Douglas!

I think you used a too high concentration.
I've started with STS last year, and my first reversed plants I had the same issue. I used a bit higher concentration as recommended in the recipe, 'just to be sure'. plants full of balls, but the balls never opened by themselves, they just fell off unopened after a while. and after prying them open, no visible pollen inside.

however, I dried some pof those balls and did manage to make seeds with it. also one plant did make plenty of visible pollen eventually, when the STS started working out after ~3 weeks.

now I aply using a pipette, just a few drops on some nodes (imo easiest is to apply once(or a few times on days right after eachother, but not a later application weeks later) when flower just started, since if there's already a small cluster of female flowers it's easier to get a drop on it without the drop falling down, the drop will stick a bit in between the pistils), concentration on the lower side so I just get a few balls, and that works way better. usually plenty of visible, fertile pollen. and I only use very little sts-solution that way.

I think ethylene is involved in ripening the male flowers/pollen production somehow, so you need just enough sts to make new flowers develop into male instead of female, but not so much that it interferes with the pollen proiduction later. and the first male flowers are more likely duds, the slightly later ones are often better.
 
I think you used a too high concentration.
I've started with STS last year, and my first reversed plants I had the same issue. I used a bit higher concentration as recommended in the recipe, 'just to be sure'. plants full of balls, but the balls never opened by themselves, they just fell off unopened after a while. and after prying them open, no visible pollen inside.

however, I dried some pof those balls and did manage to make seeds with it. also one plant did make plenty of visible pollen eventually, when the STS started working out after ~3 weeks.

now I aply using a pipette, just a few drops on some nodes (imo easiest is to apply once(or a few times on days right after eachother, but not a later application weeks later) when flower just started, since if there's already a small cluster of female flowers it's easier to get a drop on it without the drop falling down, the drop will stick a bit in between the pistils), concentration on the lower side so I just get a few balls, and that works way better. usually plenty of visible, fertile pollen. and I only use very little sts-solution that way.

I think ethylene is involved in ripening the male flowers/pollen production somehow, so you need just enough sts to make new flowers develop into male instead of female, but not so much that it interferes with the pollen proiduction later. and the first male flowers are more likely duds, the slightly later ones are often better.


Interesting! Yes, quite likely I used too much of the sts solution. While I used the same concentrations described in this post, I sprayed quite a lot of it several times. Will try out your technique next time!
 

Douglas.Curtis

Autistic Diplomat in Training
Excellent notes, thank you for sharing. Every little bit of information can be useful to someone. Awesome to see success stories. :)
 

frostqueen

Active member
I was under the impression Clarke published this in '81, definitely pre-dating Country Mon's posts.

Appreciate the accolades, I did take time to pull as much new data as possible while adding my own personal experience. :)
Thanks!

Clarke talked about rodelization in '81, which is a different technique to obtain pollen. The first fem techniques such as Dutch Passion's used it (basically stress) to create pollen, which is a bad idea.

Yours is by far the best version of any STS guide, so that's what really counts. Country Mon wanted this info to be available to everyone, so you are carrying the torch!
 

Douglas.Curtis

Autistic Diplomat in Training
I can definitely identify with both Clarke's and CM's desires to get this info out. :) Definitely not a big fan of rodelization, since it specifically works only with unstable genetics.



Keep BEing awesome! :D
 

Hookahhead

Active member
Thanks for posting this, I have been reading a bit about this the past couple of weeks. It's nice to have a clear post with all the information that I need. Cheers!
 

Ibechillin

Masochist Educator
I found Some more information/history about manipulating ethylene in plants, figured someone would appreciate.

I found a university research paper pdf on manipulating sexual expression in hemp dated February 27th 1978 from Copernicus University in Poland. It does not use Rodelization, stress or silver soloution though to supress ethylene production.

Link to pdf
https://pbsociety.org.pl/journals/index.php/asbp/article/view/asbp.1978.013/0

I also learned how long ago ethylene supression with silver was discovered as well.

"Ethylene oxide was first reported in 1859 by the French chemist Charles-Adolphe Wurtz, who prepared it by treating 2-chloroethanol with potassium hydroxide:

and discovered the ability of ethylene oxide to react with acids and salts of metals. Wurtz mistakenly assumed that ethylene oxide has the properties of an organic base. This misconception persisted until 1896 when Georg Bredig found that ethylene oxide is not an electrolyte. That it differed from other ethers — particularly by its propensity to engage in addition reactions, which are typical of unsaturated compounds — had long been a matter of debate. The heterocyclic triangular structure of ethylene oxide was proposed by 1868 or earlier.

Wurtz's 1859 synthesis long remained the only method of preparing ethylene oxide, despite numerous attempts, including by Wurtz himself, to produce ethylene oxide directly from ethylene.

Only in 1931 did French chemist Theodore Lefort develop a method of direct oxidation of ethylene in the presence of silver catalyst. Since 1940, almost all industrial production of ethylene oxide has relied on this process.
 
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