Transplanting Mature Flower Bulbs
At a certain point in time, a flower bulb planting may become so dense, with root systems so entwined, that they will start to yield more foliage than flowers. Whenever there is more foliage than flowers, it indicates a problem with root systems. (Sometimes it means that underground rodents are nibbling on the roots, or maybe even, the bulbs themselves. Other times, acidic or alkaline soil may prevent mature, if any, root growth.
When a previously blooming, mature planting ceases flower production, it likely means that the bulbs need to be dug up, gently separated with as little root destruction as possible, and replanted to the original proper depth and spacing. The best time to transplant flower bulbs is in the fall, at the normal planting time, when the ground chills down to about 55°F. Before hand, in the spring when the foliage is clearly visible, mark the area and photograph it to make fall transplant easier.
Other reasons for foliage-only and few if any flowers are insufficient cold temperatures over the winter, temperature spiking over the winter, shallow planting or the fact that prior spring foliage was prematurely cut or covered by other plant material.
If a flower bulb planting doesn't even yield foliage, it usually indicates poor water drainage, excessively acidic or alkaline soil, diseased soil or that the some bulbs have been eaten or destroyed by either underground tunneling animals (chipmunks, voles, gophers, prairie dogs) or above ground animals (deer, raccoons, rabbits, squirrels, chipmunks).