i know, old thread, but, relevant info for anywho who comes across it, like i did.
"nanners" or bananas, when these appear it is generally because of stress and it is the plants response to try and pollinate itself to perpetuate the plant. All seeds resulting will be female(at least, this is the general consensus). However, sometimes it is just due to genetics, or the fact that the plant has not yet been pollinated and its late into flowering.
this is NOT, i repeat, NOT a true hermie, and, if the trait has shown up, the appearance of nanners does not mean, necessarily, that this strain will always do that, as well as its offspring, its just one of circumstance.
True hermaphrodites have male and female flowers, the nanners are a survival trait, that, to us is very annoying. I have found that if you are diligent you can just pull off all the nanners and salvage the plant. However, it does seem to have an effect on overall yield, as the nanners come out of the calyxes. Also, there is a very small amount of pollen in the nanners, depending on the conditions of the grow room, the plant may only impregnate itself.