Why would daffodils stop blooming after 5 years?
First few years after planting, the daffodils bloomed profusely. The past two, however, foliage emerges without blooms.
Certified GKH Gardening Expert
Here is an article that will help you that discusses why daffodils won't bloom:
It could be the bulbs are just taking a rest and are building strength so that they can bloom the next year. You could try digging up the bulbs and separating them and then planting them in a more spread-out way so that they will multiply and bloom better the next year.