Silver Thiosulfate (STS) is made into a solution and then sprayed onto female cannabis plants frequently during flower to help reverse the sex of the plant so that it instead produces feminized seeds.
Only half a gallon is needed at a time for each treatment for about 4 plants. You can purchase the solution online or easily make it yourself with a few key ingredients.
How to Make your own STS Solution
- 1 Gallon of Distilled Water
- 0.5/Gram Silver Nitrate Powder
- 2.5/Grams Sodium Thiosulfate Powder
- 2 500/ML Glass Containers
- 1 1000/ML Glass Container
- Use 0.5 grams of silver nitrate in 500/ML of Distilled Water (Stir until fully dissolved)
- Use 2.5 grams of sodium thiosulfate in 500/ML of Distilled Water ( Stir until fully dissolved)
- Pour (simultaneously) both 500/ML mixtures into empty 1000/ML Glass Container
- You now have a 100% STS Solution or 1:1 ratio, still need to dilute it to a 1:9 ratio
- Combine 100/ML of STS 1:1 Solution with 900/ML of Distilled Water in a spray bottle
- You now have a 10% base STS Solution to start spraying your plants with
When to Spray
- Start spraying 1 week before putting the plants into flower
- Spray the entire plant until you see tiny run off including the leaves, stem, and stalk
- Spray again the 1st day of flower, then every 3 days for 7-9 total times (10-11 for stubborn plants)
- Spray until day 22ish – the cannabis plant should start to show signs of reversal
Sometimes leaves a purple stain behind, so use with caution and spray in a certain tent, room, or outside area.