Pruning

Pruning' is a term used to refer to when a parasite is deemed unfit or useless, and is “thrown away”. It e killed.means they will be taken out of the squad and be killed.

Overview
Having physically and mentally healthy parasites is the absolute necessity to pilot a FRANXX. However, those who have weak bodies or are otherwise not mentally fit to pilot, are usually subjected to a series of tests to change this. If this fails, they will be deemed useless and are eligible for pruning. They will be “thrown away”, which is a mild term used to refer to them being killed.

Children living in the Garden were subject to this frequently, as Squad 13 always mentioned how many children disappeared from the Garden without any explanation from the adults.

List of Parasites pruned

 * Naomi - After she and Hiro failed to synchronize during their final capacity test (manga only).
 * Nana’s former parter - After he and Nana’s FRANXX was destroyed during a battle and he was left mortally wounded (manga only).

List of Parasites eligible for pruning

 * Mitsuru - After it was discovered his unstable Yellow Blood Cells count was affecting his piloting ability. However this was resolved with a Partner shuffle.
 * 9'α - After he and Delta were left critically injured from a battle against theKlaxosaur Princess but they were saved by Squad 13. (Manga only)
 * 9'δ - After she and Alpha were left critically injured from a battle against the Klaxosaur Princess but they were saved by Squad 13. (Manga only)

Trivia

 * In the anime, it is revealed all the children who disappeared and the parasites deemed unfit were never pruned. APE ordered their pruning but Dr. FRANXX, who disagreed with APE’s ideologies, secretly kept the children in a hidden cryogenic room.
 * Naomi was among the children hidden in the room.
 * In the anime, Nana’s former partner was never pruned because he was killed in battle.