The German words “künstlich” and “künstlerisch” look and sound similar, and they both come from “Kunst” (f.), meaning “art”, but they describe quite different things:

– “künstlich” means “artificial” and is used to describe things that are unnatural or that imitate natural processes:

“Im Büro stehen nur künstliche Blumen.” – “There are only fake flowers in the office.”
“Ich habe dieses künstliche Licht satt!” – “I am sick of this artificial light!”

– “künstlerisch” means “artistic” and is used to describe anything befitting or relating to art or artists:

“Sie hat eine künstlerische Veranlagung.” – “She has an artistic temperament/disposition.”
“Er macht von der künstlerischen Freiheit gebrauch.” – “He’s making use of artistic license.”

Similar words are “kunstvoll” (in the sense of “artful”) and indeed “artistisch”.

Note: All adjectives listed here can of course also be used as adverbs (i.e. “künstlerisch” can also mean “artistically”: “Es ist künstlerisch gestaltet.” – “It is artistically arranged/designed.”)