Functionally the process of reproduction is the same as in humans. The pregnant parent’s arium will appear to expand as they carry the child until they’re born.
Bunn researchers theorize that the reason why the ariums are unaffected is because the pocket dimension creates a secondary dimension within the center of the arium which the creatures or plants or static objects may or may not see. They are unable to further determine how that works and this is likely to never be resolved.
Priests merely proclaim that it is just how the God made it and it is what it is.
Mages are always arguing with priests and like to say that it’s a form of magic inherent to Bunns.
Doulas are more practical about it and merely shrug and get on with the process of supporting any pregnant Bunns in delivering their kits.
After all, researchers, priests, and mages can argue until they’re blue in the face and red in the ears but babies are babies and have to be born.
Parent Bunn traits carry down to their children. Typically a kit will be born with the flowers/mushrooms/leaves their parents have or have a fusion of their parent's flora.
There are also random flukes in a Bunn's genetic code which may land parents with uncommon or unexpected traits. So it is possible for a Bunn to have a random flower, but the chances of that are quite slim.
Ariums however, are completely random in regards to what a Bunn is born with.
However Kits and even adult Bunns may end up changing traits as they grow older. It's possible, for instance, for an arium to change entirely without much warning.