If a planet with an upgraded defense tree is captured while the laser mine produced by that tree is active (not still attached to the tree), when that mine is subsequently destroyed, the tree will not produce another laser mine. Since the tree still has a flower attached to it, you cannot add another flower to make it produce laser mines again. If an enemy laser mine destroys that flower, attaching a new flower to the defense tree still will not make it produce a laser mine again.
I have also noticed that enemy defense trees sometimes have multiple flowers attached to it.
This is based on version 2.02 and occurs in every game, in other words the behavior is uniform and consistent. I'm posting about it since I didn't notice this issue mentioned in the release notes for 2.03 (I have Eufloria through Steam and the update hasn't propagated there yet).