Fem seed breeding: STS info and Other questions..

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Cannabis Seeds


Hi! I am a long time lurker. I think I have a few posts. I will just tell you what I want to do and ask a couple of questions, but I should just tell you what sort of responses would help. I don't have any breeding experience but I am an obsessively detailed grower and a well trained chemist. I've had great success with my tissue culture experiments and you can assume for the most part that I have the skill and materials on hand to pretty much go whatever direction for breeding. I understand that seed coat formation is a highly involved process for a plant to undertake and it both fascinates me and presents itself as a challenge that I want to take on.

What I'm trying to do is make, say a few thousand seeds by next year. I'd like to go with a "bullet proof" strain. I'd like the seeds to be 10 out of 10 in consistency, quality, rate/speed of germination, and stability in the line. I'm more interested in making sure they crack, grow strong, and finish without any nanners than anything. IOW I want the type of success that isn't a "creatively bred" plant but rather a solid seed. I have friends whose judgement I value who say that fem seeds are by nature going to be part junk. I'd like to prove them wrong, if possible, without a huge learning curve. Correct me if I'm wrong, but the name of the game is to get a healthy herm, not a pissed off she-male, so this is where technique is important.

Is tissue culture of benefit because the plants respond better or because the cross breeding and propagation rate are more efficient? Should I go traditional or at least look into TC?

Should I be looking to inbreed an already inbred line? Should I look for a fem line? Even better: what genetic should I attempt?

Do I inbreed the same plant or take two from the line? If the latter, how do I select which female to turn?

Of course the age old: CS, STS, or GA3? I can make or have access to all.

Sorry for the long post. I read a bunch but I'm hoping to get a little backup from this site. I'd like to give back in return, too, but I need to have a good plan for starters. I have had some trauma with seeds in the past, and I want to be in charge of my own seed line. I'm no idiot, and I see too many junk seeds around to just sit on my hands and just wish someone else will make good ones for me. Thanks in advance!
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If you seriously want a truely inbred line by next year, then you must start with something already considerably inbred. That is just not enough time starting with any kind of hybrid, because you'd need at least 5-8 generations to weed out rare phenotypes.

If you want no nanners, then start with a strain having little or no hermaphrodite tendency to begin with. I don't know if there are really any plants with NO hermaphrodite ability, but maybe someone knows better than I do.

Start with only females, and use colloidal silver. Because this works by blocking ethylene signalling it seems to work on every strain the same. Of course it can't change the genetics of the plants, so you won't select for hermie genes if they weren't there to begin with.

Selfing is the fastest way to inbreeding. However, it is challenging to do without introducing inbreeding depression, unless you can self a large number of plants. I am guessing you do not have a farm.

If the starting plants are already highly related, though, then you can make your life much easier. You can grow ten females, and select the most vigorous one to be the seed bearing plant. Treat all the rest with the silver and let them all pollinate her. Next, plant all of the resulting seeds from ONLY that plant, and start selecting immediately for fast sprouting, vigorous growth, stress resistance, and any of your other criteria. Be ruthless in the selection. Again, select the best one to be the seed bearing plant, and treat all the others that passed the selection with silver. This half-sibling selection will be easy and effective.

In the end, you will only have females of your strain, but it doesn't matter if you don't mind using the silver to get more seeds. If you wanted a male of the strain in the future, then you could get one by repeatedly backcrossing any random male to the inbred female line.

In my opinion, tissue culture would be a complete waste of time for a breeding project like this. Just start growing.


Jun 9, 2011
What I'm trying to do is make, say a few thousand seeds by next year. I'd like to go with a "bullet proof" strain. I'd like the seeds to be 10 out of 10 in consistency, quality, rate/speed of germination, and stability in the line. I'm more interested in making sure they crack, grow strong, and finish without any nanners than anything. . Correct me if I'm wrong, but the name of the game is to get a healthy herm, not a pissed off she-male, so this is where technique is important.
lets get this str8 right away.. there is no such thing as a health herm... You want a strain which has no reports of any herm ever.. You want to stress test this strain to see if there are herm genetic "just below the surface"... Never use the word herm when breeding... You want to reverse a female to male... Stronger the female the better...
Should I be looking to inbreed an already inbred line? Should I look for a fem line? Even better: what genetic should I attempt?
this is up to you... you get better vigor with crossing two IBLs. But then you need to know 2 strains real good not 1.
Do I inbreed the same plant or take two from the line? If the latter, how do I select which female to turn?
Ok here is a auto non auto related matter... Autos cant be kept as clones so testing is done on a strain line... when you have a cloneable plant it can be tested and saved for use.. You need to know your gene pool.. With a non auto line you can grow out 50 plants select a top notch female ..stress test her and move forward.. not so with auto... With autos its best to reverse multiple plants and then select a winner...
Of course the age old: CS, STS, or GA3? I can make or have access to all.
STS and CS seem the best... GA3 not so much useage.. IMO most commercial breeders use sts, although I have no data that says its better... than CS.
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Clone Ranger

I'm a couple of weeks away from doing a CS vs STS shootout with some F19s cres - you may know where I got them and where I got the Sodium............
Have heard STS produces more pollen - keep you updated on it if you want.
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Jun 9, 2011
Here is some info...

The properties of STS reported that its complex ions are more mobile and can be transported by the vascular system.

Perhaps this shows the difference between these stimulants.


The STS complex was used because it has much greater mobility in plant tissue than uncomplexed silver ion (16).
(16) VEEN H, SC VAN DE GEIJN 1978 Mobility and ionic form of silver as related to longevity of cut carnations. Planta 140: 92-96


While attempting to increase the longevity of cut carnations, Veen and Van de Geijn (1) demonstrated the manifold mobility of the silver ion in the anionic complex silver thiosulphate, [Ag(S203)2]3-, over that in AgNO3. The anti-ethylene action of this compound prompted us to assay its potential in sex reversion of gynoecious cucumbers. Initial trials indicated that Ag(S203)2 induced male flowers much the same as AgNO3. A more detailed experiment was carried out late in the fall of 1978.
(1) Veen, H. and S. C. v.d. Geijn. 1978. Mobility and ionic form of silver as related to longevity of cut carnations. Planta 140:93-96.


The commercial application of silver as an antiethylene treatment was made possible by the discovery by Veen and van de Geijn (1978) that the silver thiosulfate (STS) complex was stable and highly mobile in the vascular system but was still very effective in preventing ethylene action.
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Jun 9, 2011
How To Reverse Sex Using Silver Thiosulfate Solution
The following is a safe, inexpensive, and successful method for reversing the sex of female cannabis plants. Individual plant responses may vary based upon strain, but I can verify that this process is fully effective in stimulating profuse staminate flower production.

This process can be used to:

A: create new feminized seeds from solitary prize mothers that you currently have
B: create interesting feminized-seed hybrids from different prize strains that you currently have
C: create feminized seeds for optimum outdoor use
D: accelerate the "interview" phase of cultivation, in searching for interesting new clone-mothers
E: reduce total plant numbers- great for medical users with severe plant number restrictions
F: increase variety, by helping to create stable feminized seedlines to be used as an alternative to clones

At the bottom of this post are some specific details about the chemicals used, their safety, their cost, and where to get them.

It is important to educate yourself about cannabis breeding theory and technique prior to using a method like this one. Here is a link to Robert Clarke's "Marijuana Botany", which is a very good reference.

"Marijuana Botany" by Robert Connell Clarke
(unfortunately missing the appendices)
Marijuana Botany

It is also important to use basic safety precautions when mixing and handling these chemicals, so read the safety data links provided. The risk is similar to mixing and handling chemical fertilizers, and similar handling procedures are sufficient.

Remember: nothing will ever replace good genetics, and some of your bounty should always go back towards the professional cannabis breeders out there... the ones who have worked for many generations to come up with their true-breeding F1 masterpieces. Support professional breeders by buying their seeds. Also, order from Heaven's Stairway. Not that they need a plug from me, but they are very professional and provide very fast service worldwide.
Preparation of STS:

First, a stock solution is made. It consists of two parts (A and B) that are initially mixed separately, then blended together. Part A is ALWAYS mixed into part B while stirring rapidly. Use distilled water; tap water may cause precipitates to form.

Wear gloves while mixing and using these chemicals, and mix and use in a properly ventilated area. A mask will prevent the breathing of any dust, which is caustic. STS is colorless and odorless, and poses minimal health risks if used as described here. (See material safety data sheet links below). Note that silver nitrate and STS can cause brown stains upon drying, so spray over newspaper and avoid spilling.

Part A: .5 gram silver nitrate stirred into 500ml distilled water
Part B: 2.5 grams sodium thiosulfate (anhydrous) stirred into 500ml distilled water

The silver nitrate dissolves within 15 seconds. The sodium thiosulfate takes 30-45 seconds to dissolve.

The silver nitrate solution (A) is then mixed into the sodium thiosulfate solution (B) while stirring rapidly. The resulting blend is stock silver thiosulfate solution (STS).

This stock solution is then diluted at a ratio of 1:9 to make a working solution. For example, 100ml of stock STS is added to 900ml of distilled water. This is then sprayed on select female plants.

Both the stock STS and the working solution should be refrigerated after use, as well as the powdered chemicals, to avoid activity loss. Excess working solution can be safely poured down the drain after use (with ample running water) with negligible environmental impact. It's pretty cheap.

Each liter of stock STS will make ten 1-liter batches of working solution of STS. With the minimum amount of base chemicals ordered from Photographer's Formulary (see link below), this means that each 1-liter bottle of working solution STS costs less than 9 cents, and can treat 15-20 mid-sized plants. That's 200 1-liter batches of STS for $18. Note that the distilled water costs far more than the chemicals.

The STS working solution is sprayed on select female plants until runoff. Do the spraying over newspaper in a separate area from the flower room. You probably won't smell anything, but ventilate anyway. You now have what I call a "F>M plant"; a female plant that will produce male flowers.

After the F>M plant dries move it into 12/12 immediately. This is usually done three to four weeks prior to the date that the target (to be pollinated) plants will be ready to pollinate. Response times may vary slightly depending upon the strain. More specific times can be determined by trial with your own individual strains. In my trials it took 26 days for the first pollen. 30-35 days seems optimum for planning purposes.

So, assuming that a target plant needs 3-4 weeks to produce fully mature seeds, a strain that takes 8 weeks to mature should be moved into flower at about the same time as the female>male plant. A target plant that finishes flowering in 6 weeks needs to be moved into flower later (10 days or so) so that it doesn't finish before the seeds can fully mature.

A seeded individual branch can be left to mature on a plant for a bit longer, while harvesting the other seedless buds if they finish first. Just leave enough leaves on for the plant for it to stay healthy.


Within days I noticed a yellowing of the leaves on the F>M plants. This effect persisted for two weeks or so; after this they became green again, except for a few of the larger fans. The plants otherwise seemed healthy. No burning was observed. Growth stopped dead for the first ten days, and then resumed slowly. No stretch was ever seen. After two weeks the F>M plants were obviously forming male flower clusters. Not just a few clusters of balls, but complete male flower tops. One plant still formed some pistillate flowers, but overall it was predominantly male.

It is strange indeed to see an old girlfriend that you know like the back of your hand go through a sex change. I'll admit that things were awkward between us at first.

When the F>M plants look like they may soon open and release pollen, ( 3-1/2 to 4 weeks) move them from the main flower room into another unventilated room or closet with lighting on a 12/12 timer. Don't worry too much about watts per square foot; it will only be temporary.

When the pollen flies, move your target plants into the closet and pollinate.

A more controlled approach is to isolate the F>M plants in a third remote closet (no light is necessary in this one, as they are releasing pollen now and are nearly finished anyway). In this remote other closet the pollen is very carefully collected in a plastic produce bag or newspaper sleeve and then brought back to the lighted closet, where the target plants are now located. If this is done, be careful to not mix pollen types by letting the F>Ms dust each other. Avoid movement, or use yet another closet.

Take special care to not let pollen gather on the outside of this bag- a static charge is sometimes present. Drop small open clusters of blooms inside and then close the bag at the mouth and shake. Important: next, step outside and slowly release the excess air from the bag, collapsing it completely, so that pollen doesn't get released accidently. Point downwind; don't let it get on your hands or clothes.

This collapsed pollinated bag is now very carefully slipped over only one branch and is then tied off tightly at the mouth around the branch stem with a twist tie or tape, sealing the pollen inside. Let the bag inflate slightly with air again before sealing it off, so the branch can breathe. This technique keeps the entire plant from seeding. Agitate the bag a bit after tying it off to distribute the pollen. Don't forget to label the branch so you know which seeds are which. Other branches on this same plant can be hit with different pollen sources.

If no lighted closet is available, the plant can be moved back into the main room, but- be very careful: pollen is sneaky. After 4-5 days, the bag is gently removed and the plant completes it's flowering cycle.

Yet another method has worked well for me. I position the target plants in a non-ventilated lighted closet, and then I collect pollen on a piece of mirror or glass. This is then carefully applied to the pistils of one pre-labeled branch by using a very fine watercolor paintbrush. Care is taken to not agitate the branch or the pollen. No sneezing. The plant needs to be in place first; moving it after pollination can shake pollen free and blow this technique.

Regardless of technique, at completion you will have feminized seeds. Let them dry for 2-4 weeks.
About the chemicals:

Silver nitrate is a white crystalline light-sensitive chemical that is commonly used in photography. It is also used in babies' eyes at birth to prevent blindness. It can cause mild skin irritation, and it stains brown. Avoid breathing. I didn't notice any smell or fumes, but ventilation is recommended. Be sure to wash the spray bottle well before you use it elsewhere; better yet: devote a bottle to STS use. A half gram is a surprisingly small amount; it would fit inside a gel capsule.

Here are links to some safety data. A Google search will bring up more information if needed.

Silver Nitrate info:
ICSC:NENG1116 International Chemical Safety Cards (WHO/IPCS/ILO) | CDC/NIOSH
http://www.lions.odu.edu/~redwards/... solution.pdf

For a realistic hazard level comparison, here is a link for the safety and handling data for Ammonium Nitrate, or common fertilizer:

Sodium thiosulfate is also a white crystalline chemical commonly used in photography; it is used in photographic fixers. Same general cautions apply, minus the staining. This formula uses the anhydrous type. Non-hazardous.

Sodium Thiosulfate info:


Where to get the chemicals:

Photographic chemicals, photo chemistry, photo processing equipment, photo chemicals
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Clone Ranger

Hey cres - thanks. I'll print that out (again - Mrs X put it in the bin I think). Doing two fems CS and 2 STS.
Then they go to see other fems waiting.
I've found a lag in the CS'd fems in the past - so should I flip the STS plants a week or two before the receiving fems?
All help, as always, appreciated.


Jun 9, 2011
Timing is always an issue, most sts treatment I have done delay onset of male flowers by a week or two...so if your flowering a six weeker then be careful.

I edited the title of this thread and gave it a sticky as many are looking for sts info...
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Epic Genetics

i saw mention of lack of pollin when reversing a plant with CS , so id just like to comment from my own experience when useing it , when made and used properly i reverse a small plant only , a plant that only a week to 10 days before was a freshly rooted clone (when not doing autos) , this small plant a foot tall at best pollinates my entire 4X4 room with ease

peace :cool: