Pflanz was born in July 1914 in Ichenheim, present-day part of Neuried, at the time in Grand Duchy of Baden of the German Empire.

Pflanz claimed his first aerial victory on 30 April 1940 during the early Phoney War period over a Potez 63 northwest of Merzig.

On 28 November 1940, Pflanz probably shot down Royal Air Force (RAF) ace Flight Lieutenant John Dundas of No.

He received the award from Feldmarschall (Field Marschal) Hugo Sperrle with fellow JG 2 "Richthofen" pilots Leutnant Egon Mayer and Oberleutnant Erich Leie on that day.

The triple award presentation was recorded by the Deutsche Wochenschau (German Weekly Review), a newsreel series released in the cinemas.

On 31 July 1942, Pflanz was shot down and killed in action in his Messerschmitt Bf 109 G-1 (Werknummer 10318—factory number) south of Moncheaux.

[15] This and the ♠ (Ace of spades) indicates those aerial victories which made Pflanz an "ace-in-a-day", a term which designates a fighter pilot who has shot down five or more airplanes in a single day.