[4] Krohn mostly preferred not to write under his foreign surname, but either adopted a pen name or worked as part of a collective, such as the fennomans, of which he was a leading member.

Under his most notable pseudonym Suonio, he published poetry; e.g. Mansikoita ja mustikoita 1856–61 ("Strawberries and blueberries") and Kuun tarinoita ("Tales of the moon").

As Suonio, he worked as editor of Suomen Kuvalehti and translated many of Sir Walter Scott's novels, such as A Legend of Montrose.

An important contribution to a history of Finnish literature was Krohn's doctoral thesis Suomenkielinen runollisuus ruotsinvallan aikana (1862).

His daughter Helmi Krohn, also an author, married Eemil Nestor Setälä, later the acting head of state of Finland in November 1917, after the abdication of Nicholas II of Russia.