From Gardener's Supply (www.gardeners.com)
Unfortunately, once daffodils have bloomed, they don’t age very gracefully. The spent flower heads turn brown and the foliage gets limp and begins to flop. Not a pretty sight.
Though it’s a good idea to remove the spent flower heads, you should not remove the daffodil’s foliage. While the leaves are green, the plant is producing energy for next year’s flowers.
If you’d rather not look at or bother with that fading daffodil foliage, pair your daffodils with summer-blooming plants, such as daylilies! The daylily foliage will emerge just after the daffodils have bloomed, and will gradually cover the fading foliage.
The only maintenance a daffodil-daylily bed will need is a quick raking in very early spring to remove the old daylily foliage. Both of these plants are hardy, pest- and disease-resistant, tolerate poor soil, and thrive in full sun or partial shade. Daffodils should be planted in the fall. Daylilies may be planted spring or fall.