Whew, the Edelweiß has a rather varied and tangled history when it comes to its use as a symbol (and I'm a bit short on time right now...).
The Edelweiß is the national flower of Austria (well, both the Edelweiß and the Enzian (gentian in English) are).
Due to it growing mainly higher up in the mountains, it has become a symbol of courage (as in, you have to be courageous to climb up to pick them, I guess), especially in Romanticism.
During the Third Reich, it was used by both the Nazis ("Edelweiß-Division"
https://en.wikipedia.org/wiki/1st_Mountain_Division_(Wehrmacht)) and antifascist groups ("Edelweißpiraten"
https://en.wikipedia.org/wiki/Edelweiss_Pirates).
And those are just a few of the symbolic uses of this flower...