I know about Cornell CALS, but what are some other great schools for plant science?
UC Davis, UC Riverside come to mind.
Are you interested in a particular crop? That could narrow your choices a bit.
What state are you in? Your home state should have a decent college of agriculture at at least one of the public universities. If not, there is likely to be an agreement with the college of agriculture in a nearby state that will offer you in-state tuition rates.