Where to Find and Catch Tangrowth
From Pokemon Go Wiki
Tangrowth are found and captured in Nest and Habitat locations.
Nests
Tangrowth Nests are locations that consistently spawn Tangrowth.
Habitats
Tangrowth Habitats are spawn locations where Tangrowth 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: