The blue flower was a symbol for the German Romantic movement. It originated in the works of the German author Novalis, and eventually came to represent bittersweet longing, the Sehnsucht that Lewis spoke of.
“The ‘blue flower’ is unattainable and is to remain unattainable. Romantics expressed a longing for home and a longing for what is far off; Schiller called the romantics ‘exiles pining for a homeland’,” write Finnish authors Petri Liukkonen and Ari Pesonen on their page on Novalis.
The blue flower, or "Blaue Blume," of Sehnsucht
"Klingsors Zaubergarten (The Magic Garden of Klingsor)" by Gemälde von Angerer dem Älteren. Note the blue flower gleaming in the center.
