it's often environmental. there is generally more than one factor with genetics playing a part. some plants may have the tendency, but will need a particular stressor to turn.
I do agree with this statement, Enviromental factors; that includes us the human. We are the mayor enviromental stressor for any pheno, or are we not part of the environment. Every time we water, or change the photoperiod, or defol train or feed we are the environmental stressor that triggers any change.
The only genetics I find to be highly unstable are landrace genetics, why I think that? because these phenos have been under stress for years and years by mother nature, therefor develope a selfpolinating instinct in order to preserve the genes and pass it to a new generation. All phenos have it hence they are all one same species Cannabis Sativa.
We can change that selfpolinating instinct by acting as enviromental catalist to breed out that selfpolinating "trait". It would take hundreds and hundreds of phenos to get that stable one...
Anyways, I totally consider myself as part of the enviroment thats why I do my plants like I do.
Commercial breeding has made a business selling unstable seeds marked as "feminized" as we know today there is no truly female genetic or pure male genetics (unless we talk about genetically modified organism).
We can debate with facts if that is the way we want to take it, but we also experiment every time we grow. I chose the science of repetition and observation.
Dani, a few years ago I grew some Thai - Malawi (Golden Tiger) outside in pots. Thinking they may be induced to flower early I carried each pot into my shed every night to insure they got only 12 hr of light. It worked for five plants, but two hermied quickly. I haven't done that since, but it works and if you have any strains prone to hermaphroditism forced flowering can be a stressor.
I understand, Thai (landrace) and Malawi (landrace) are probably stressed out very easy because lets face it as much as we try we can never fully replicate the conditions of Africa or Thailand in our grow space.
Things so subtle like the amount of rain fall, the amount of UV index in the sunlight, the angle of the sun, the humidity, I would go as far as the composition of the soil... Its impossible we can dial all these factors in our grows.
For me Sativas are by far the hardest to keep from hermie because we dont live on/near the equator, and they are plants that dont have more than 1 hour of fluctuations on their photoperiod year round. I dont use light schedules like 18/6 anymore when I grow sativas. I use 13/11 or 1230/1130. I have gone as far as to see sunlight patterns around the equator and follow this to try and mimic the photoperiods around the equator.
I love Sativas and I love them even more when they are landraces.