Not logical at all. Had to make assumptions at the start just to get going.

R1: C2-C3, C5-C6, C8-C9, C11 - Then mirror it. Apply that sequence to every row and column that is the same.

Thanks for the tips LordHighJim. Was solving a good chunk of it, but messed up somewhere.

Thanks, LordHighJim, didn't even want to try before.

Complete guesswork required.

If stuck, the crosses are at the corners and the flora is centered.

Thanks für the spoilers LordHighJim. Poor puzzle, nice pattern.