Alpine Park & Gardens is a really neat place in Columbia to get married outdoors. It wasn't quite green and lush by April of 2009 but it was still a really beautiful venue. I photographed a wedding there last April and it was perfect! Here's a link to those photos if you are interested: http://blog.erikajacksonphotography.com/2009/04/married-kathryn-tim.html
I'm with Erika for Alpine. Lots of gorgeous weddings there. If you are having a small wedding, I'd definitely think about contacting Shelter Gardens. It's so gorgeous there so it has the possibility of being a gorgeous venue.
I am sure that you have already found a location to hold your ceremony?? But just in case you are still needing ideas: Martin Luther King Jr. Memorial at Battle Garden's is a beautiful location. The cost is $55. It's really cheap, but SO pretty.