Fencerows are interesting microenvironments. Say the land is cleared, good for pasture or row crops, and the necessity for fencing is at once apparent, either to keep critters in or out.
So, across this open area is now the perfect perch for meadow birds and others that will tolerate the newly opened area, lacking the original biodiversity, including, most likely, trees.
So, foraging birds perch now and then on the fence. And do what birds do. Look around. Make noise. Excrete.
Seeds collect here and there, some germinate, some live longer, and a microenvironment develops along the fence line. Where these roses came from, I’m not sure, but they are striving on this old fenceline (the fence is now gone)….