Cannabis, being wind pollinated, is a natural out-crosser. That is what it wants to do to be at its healthiest.
Some plants like tomatoes almost always self pollinate (when you breed tomatoes you have to open the dioecious flowers by hand and remove the stamens before they pollinate the female parts, and then use pollen from another variety’s flower.
Other plants such as Brassicas REALLY try to avoid being selfed by having a biological mechanism called ‘self incompatibility’ to stop it happening.
Cannabis will often eventually produce male flowers on the female plant in the absence of any other pollination… so i guess it is somewhere in the middle. It prefers out-crossing but will take inbreeding if that is all that is available. (remember cannabis doesn’t exist for our consistent smoking pleasure! - that is something we impose upon it)
Inbreeding depression depends (amongst other things) on the population size. If you are repeatedly inbreeding and just using a pair of plants each time then you might start to see it in 3 or 4 generations (depending on what you start with). This is why using larger populations of plants is preferable (but more complicated), and this is why i will often use all the decent males in a population of plants rather than selecting just 1 (i think using all the good males is better for preservation runs, and if you aren’t going to progeny test all the males then my philosophy is ‘if you cant select properly then dont select’ - so i will leave those genetics in the line for other people to select from in the future rather than just picking what i think is the best looking male and losing genetics from the rest. i don’t have the space for proper progeny testing of multiple males, and also reduces the risk of inbreeding depression. Mr.Greengenes of Cherry Bomb fame taught me to do this, and his knowledge and opinion is one i value.
Smokers prefer lines that are consistent and inbreeding obviously helps achieve that… but it is in conflict with what is best for the health and vigor of the plant, and the skill of the breeder is to get the balance right and create a variety that smokes consistently well and is still healthy.
Another way to get consistent progeny is to do an F1 of two consistent varieties. This is what happens more often in general Farming and Horticulture because you get hybrid vigor as well.
Yes it is fascinating!
VG
If anyone wants to dive deeper into the science of plant breeding there is a great book called
‘The Principles of Plant Breeding’ by Robert Allard. The second edition really goes into how plant populations work in breeding.
Its a very expensive book but i ordered it from the Library and then photocopied all the pages!
VG
the interesting thing is so many people fear what ‘big brother could do if someone finds out’. has anyone looked into the criminal offenses for growing too much? i know other states are a lot more progressive but my state has confiscation clauses and a $250 fine, for an unlimited number of plants. many states i’ve seen don’t even classify growing over legal limits as a ‘felony’. where all the charges come from is trying to make money selling your goods. that’s a big no-no. tons of felonies there.
similar situation with veggies except they’re mostly ‘legal’. no one cares about how many veggies you grow in your backyard. the minute you make six figures selling your veggies, that’s when people turn heads. it always follows the money. don’t make any money and just grow your own and no one will bother you. that’s all i really have to say on the matter ^^ it’s really not complicated at all.
@Acro - ever grown a landrace? several? reason why i ask is i notice a lot of people who work with modern plants haven’t experienced a lot of things cannabis has to offer. they are bred and managed for one thing only : profit/production. there’s so much more profit to be made when you don’t have to hunt for males, don’t have to select the good ones, and so on…
i agree. i do have to point out though that i’m not speaking from “old belief” i’m speaking from experience. the modern fems i’ve germinated over the last 5 years from half a dozen different breeders… all of them have issues. i’ve grown enough now to notice a few subtle things (which are subjective for sure). as a breeder, i have selected traits desirable for ‘growing’ and traits desirable for ‘flowering’. fems are excellent for flowering. nearly every fem i’ve grown has made wonderful flowers. it makes sense because fem x fem breeding is purely for flower! but when i look for ‘growing traits’ those NEVER come from fem seeds. additionally sometimes i do research to see if the market has made certain plants available yet… like full-auto long-flower sativas, auto mutants, monster fems, and the like… i’ve seen some AMAZING outdoor plants, but never do i see them mention they’re from fem stock.
VerdantGreen makes an excellent point:
Ah this one?
You can actually kinda avoid inbreeding depression by working several parallel lines and crossing them to restore vigor in the released seeds.
Inbred lines are more useful to create hybrids than to be used directly in production, as they’re used to breed true fro certain trait(s).
I’m currently reading that Allard book, but oh boy is that and arid book 
From this book:
“There are also great differences in the effects of inbreeding, ranging from little or no deterioration in such crops as hemp and the cucurbits to such drastic effects in others, for example, alfalfa, that few lines can be carried beyond the second or third selfed generation.”
No, but i have that one and it is good too. Got that for 10 quid because it had a torn cover!
Yes, very dry… and i won’t pretend to completely understand all of it !
Hey thanks @HolyAngel I was searching after this one!
Idk shit about breeding, I’ve only tried once and got very lucky. But I’ve only grown 1 pack of fems from Ethos and it was lackluster to say the least. Reg seeds all day. Preferably f1’s. I like the vigor and variety.
Edit: I’m also a 1 tent operation so I just have a 3x3 to work with. I can pop 9 seeds at a time and veg them out in 3gal pots and pull the males. Recycle the soil. It’s not that deep lol
Oh man, helps if I can read 
It took me some hella google-fu but I think I found the first edition
Brilliant! - ive never seen the first edition so thanks. The second edition came out in '99 so a lot later.
Thanks! 
Halfway related while we are on the topic… ecornell has a hemp genetics and breeding certificate. I took it. $3500 is way overpriced but they do give you access to some really cool pieces of information.
P.s thanks for the books and references, holy and verdant
Good thread…
…
Came to see the argument;
Left off finding tons of info…
Here’s another classic book : Selection method in plant breeding by boz and caligari (courtesy of @Mithridate)
Oh nice, thanks! Added to the google drive ^^
You have a folder there with books?
ahah, google must have hard time hosting that much lol. Thanks!
oO some good ones over there!
More fems he said beating his drum and playing guitar loudly.