Well, they are certainly not very deep. I divided mine last fall and they are up, including the two that evidently fell down into my lawn and are as big as the ones in the bed. If they were flopping, you might try using a heavier mulch around them to prop them up.

If you are talking about Crocosmia Montbretia, it is wildly prolific and chokes itself out very easily. I pull up as many as I can every year (simply yank them out and compost them) and still have more than enough in every subsequent year. Other cultivars are much better behaved (Solfaterre and Emily MacKenzie), and some are even downright stingy about multiplying (Lucifer).