'Blumenpflücken' was a German operation against the resistance movement in occupied Norway, planned and carried out by the Gestapo and Sicherheitspolizei (late 1944/early 1945).

The operation was planned by SS-Hauptsturmführer Ernst Weiner, a Gestapo officer, and was a part of the Gegenterror schemed as the means to weaken the Norwegian resistance. The purpose was not to terrorise or liquidate central resistance leaders, but rather to capture and kill other Norwegians known to be against the German occupation, and to conceal the real purpose. The killings were made to look like the actions by the Norwegian resistance, specifically the communist parts of it. Many believed the deception well into the 1990s, and during the war, even some of the German participants believed that the initiative had come from SS-Hauptsturmführer Siegfried Fehmer or the Reichskommissariat Norwegen. It remains unknown whether or not the Statspolitiet (Norwegian Nazi police) knew of the undertaking.

According to one author, Weiner participated and, between 12 June and 1 July 1944, shot the first three of the 11 victims: these were Einar Hærland, long thought to have been liquidated by Norwegians, Sigurd Roll and Gunnar Spangen. According to another writer, Sigrid Hammerø was also killed, the operation’s only female victim. The next seven killings took place in November and December 1944. The first was carried out by two Norwegian perpetrators and a German helper, Erwin Morio. The next three were carried out by Germans only. The next killing was by two Norwegians, and the last three were carried out by Nickerl or Heinz Vierke with Norwegian helpers. The last victim, Georg Henrik Resch, killed in Drammen on 6 January 1945 was the wrong person: the two attempts had failed on 4 September and 30 October 1944. All but three of the killings took place in Oslo or Aker.

Of the 11 killings that resulted in trials after the war, there were convictions in each case but that of Vierke. Weiner was interrogated as a part of the post-war legal purge in Norway, but was not convicted: on 17 December 1945, while being held at the Akershus fortress, he is claimed to have shot and killed himself and a fellow prisoner. However, it has been claimed by fellow inmates that he was murdered as an act of revenge.