there is also a method used called "Rodalization"
A female plant will produce male bananas on its own flowers at the end of it's blooming cycle. This is not to be confused with a hermie plant. The male bananas do not show up until 2 weeks or more after the flowering cycle has peaked. You sacfrice one of your plants for quality smoke but you eventually get female seeds.

Once you collect the pollen you simply re-distribute it on a unpollinated female and it gives you organically grown female seeds. Soma uses this method. Here is a link from High Times
click here

image 1 is a somatooth # 2 that is now 28 days past peak. I removed the top half and am rodelizing the bottom half. She is starting to produce male bananas to try to keep herself alive.

image 2. The male bananas are starting to appear on the buds at 14 days past amber/bursting trichomes/peak. Some strains take longer and I have seen some not produce any at all.