very sweet. excellent idea for a poem. nice comparison.
okay, adult crticism, since you posted on an adult site:
dandelions don't lose color at night; they close up. it's really cool to watch. so, lesson #1: write about what you know. that being said, the 'help' page on this site has some great references. this is one of my favorites:
http://www.uni.edu/english/craft/imagery.html
keep up the good work!