This
https://en.wikipedia.org/wiki/Age_verification_system#Legal_... will begin to give you at least feel for the field.
If it reflects reality the areas which currently have rules are porn, social media and video games so whatever your mysterious plants are they're unlikely to have restrictions applied to them . Even those controls are restricted to certain geographic areas.
Admirably, in my opinion, the exception to this is Germany, which has gone some way to recognizing that perhaps allowing five year olds watch people having their heads blown off might be at least as problematic as letting the toddlers watch porn, still no mention of pictures of plants though.
I'm not a lawyer and I don't speak German so anyone who's interested in the German rules should confirm what I've said for themselves https://www.landesrecht-bw.de/bsbw/document/jlr-JMedienSchSt...) .