It is not known precisely where ass flowers came from, but the current theory is that some mad scientist created a flower homunculus by injecting ass DNA into a flower egg. Then they would have presumably inserted it into the brain of a Rothot, directly through the Eustachian tube. Inside the brain, the excess technology and information would seep into the egg, allowing it to actually make sense, thereby making ass flowers come into existence.
This theory has not yet been reproduced since Rothots don't have brains.
The life of an ass flower begins as an ass seed, which is encased in a small butt. This seed is carried on the winds, away from its mother. The small butt can also fart, allowing the seed to steer, and even allowing it to spread when there is no wind.
Once the seed lands on the ground, the butt will fart one last time, pushing the seed deep into the ground with all its might, and also exuding a pungent smell that keeps animals that might want to eat the seeds away. Then the butt decays and nourishes the seed within, which will go through several stages of growth, eventually reaching adulthood. Upon adulthood, it is a flower which may range from 10 centimeters to 5 meters tall, covered in small asses. Some adult ass flowers actually have human sized asses on them that you can touch, and that's kinda nice, but then its defense mechanism kicks in and it farts on you and you die which is sad because then your family has to pay for funeral costs and stuff.
Once adult, the ass flower begins farting out pollen, which will pollinate other ass flowers. The ass flower can also pollinate itself in a process called "autofart". Pollinated ass flowers will fart out ass seeds, and so the cycle continues.