These roses will stack but they are not able to be un-stacked. I first encountered this with the moving crate - if they get put back into the crate (which I guess that is for another post but WAY more than just add-ons go back into the moving crate) they will all stack together. I have had this happen twice with the moving crate - had to page a GM to unstack them for me. I have made it a point to TRY to remember to pick them up before I go into customization mode so it isn't an issue. However, today I found another circumstance in which these roses will stack - using the [dump command. If you dump them from one container into another they fuse together.
Not relevant to the safety of the shard or anything but wanted to pass it along anyway And please do not delete them! I love them