I planted calla lilies in large pots several years ago and they bloomed profusely each year for the first three years. Last year there was lots of foliage, but no blooms.

Last fall I put them in the ground. They came up this spring with lots of foliage, but again, no blooms.

Have the bulbs gotten too crowded? Should I separate them? Also, should they be replanted nearer to the surface of the ground (the way that iris and some others need to be every few years)?