What to do to avoid the overinfestation of Crocosmia in the entire bed?

[abodelook]

I really love the architectural appearance of Crocosmia, though, I heard that they are rather aggressive in their growth when they like the soil. I am examining some of the garden partitions and pots on abodelook to see whether I can order them better. But has no one tried to grow them in sunk pots to prevent the corms wandering too far? I do want those gaudy mid-summer flowers, but I do not want them to smother up my more tender perennials. Tell me your tricks of keeping them in hand!