Oriental Poppies I almost hesitate to mention these because they present a problem of theirown. But Oriental poppies in bloom are a gorgeous sight - and their foliage shoots up very quickly in spring, effectively hiding any bulbs that need hiding. Unfortunately, they then suffer a similar fate and need something that will hide their own decaying foliage. Actually, I just wade on in and cut it down when it starts to look bad - but you can hide it quite well with mature clumps of daylilies. So while the daylily alone may not be the best plant for hiding yellow foliage, using it in conjunction with oriental poppies will give you a long and spectacular flowering display.
Weeping trees do a wonderful job.
The spring bulbs peek through their denuded spring boughs, but are hidden when the tree leafs out. But deep purple or even pink tulips look great with the pale pink of the cherry blossoms. And don't forget pansies. They love to bloom in cool weather and look quite charming with spring bulbs - especially the smaller ones such as crocuses, snowdrops, chionodoxa and muscari. And they will spread nicely as the bulbs start to deteriorate - so that you will hardy notice when the bulbs make their exit.