One cause could be the disease Staganospora. This is what ours have and Ray
says that any good fungicide should be sprayed onto the leaves two or three
times in spring.
The symptoms are of course, no flowers but also premature browning of the
tips of the leaves and dying back. Because of the too-early die back, the
bulbs get no nourishment, so they form no flowers for the next spring. A
friend tells me this has affected a patch of snowdrops in their garden, too.
--
Sacha
www.hillhousenursery.co.uk
South Devon
(remove the weeds to email me)