Possible Clues:

• Drug agent I figure out on reflection is a plant
• Suspicion so continued over self-regarding youth
• Poor Russians catching cold in plant
• Susan cries out, dropping end of blue flower
• Stood up cold topless Dutch egotist
• Cuss -- rains damaged flower
• Beautiful young Greek who fell in love with his own reflection
• One of a poetic host's urns is cast almost sloppily
• Bloomer as drug agent sends out missing drug
• Trumpet-bearer at the front calling Russians to assemble