Possible Clues:

• The blooming yellow cover of the crazy thing up there
• Flower in Wordsworth's 'I Wandered Lonely as a Cloud'
• Vivid yellow
• Part of the host to please poet
• Five hundred wrongly laid off - it's a bloomer
• Flipping hat off, notice flower
• Narcissus' cousin
• Plant needs to have 500 laid off, sadly
• One of those with a trumpet heralding spring
• Cover separated from plug turns yellow