We used Valley Perennials. They're about the only game in town, but the woman who runs it is really great. We had them do the arrangements for us based on the specific flowers we wanted, but they will probably sell the flowers to you as well.
If you don't have any luck with Valley Perennials you can always try Dubuque.
Here's a link to Valley Perennial's location on google maps: http://goo.gl/maps/nOPKG
Garden Party Florist
We are a custom wedding florist and can help you with your flowers.
Congratulations on your upcoming wedding,
Click on each tool to see a sample.