Where to Find and Catch Cottonee
From Pokemon Go Wiki
Cottonee are found and captured in Nest and Habitat locations.
Nests
Cottonee Nests are locations that consistently spawn Cottonee.
Habitats
Cottonee Habitats are spawn locations where Cottonee is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: