Beginner Gardening: Peonies spreading?, 1 by VooDooU

VooDooU wrote:
Im stumped... I have read a bit on peonies trying to educate myself but I cant figure out this particular weirdness. The issue is I have peonies coming out my ears! If I had corn that would actually be a true statement! Ill start out with saying that we just moved in this past December.

In the last photo is a small section of what one half of back fence looks like(or did a month ago, nearly all have bloomed at this point). Big healthy and adult peonies. They all started growing at the same time and as you can see developed well. On the other side of the yard we assumed just didnt have any because nothing grew and there is a natural break in the yard with a stone path. I decided id put the garden up there since it wouldnt interfere with the flowers. Fast forward 4-6 weeks and I see peonies coming up is some weird spots like several feet away from the fence and mixed in what would have been the lawn if I hadnt have tilled it up. As you can see in the pictures they are coming up in a big area and really late. Now the ones outside the garden have been mowed down at least twice but not until the other peonies were full bushes and had budded up.

I dig up several and sold them or gave them away so these are actually even later to come up. So any insight would be great but the conundrums are how are they spreading like this, why are they so late to pop up or do you think they were possibly planted like this at some point and werent maintained.