Unknown flower - City Park Botanical Garden

This photo was taken with a Nikon 105mm 2.8. I am not sure what kind of flower this is. There were a couple of volunteers weeding in the garden. They were interested in the pictures I was taking, so I set this one up to show them. I took the shot then let them look through lens to see how close the lens would get. They said seeing it helped them appreciate the flowers more than they already did.