A few weeks ago I was at the farmer's market and saw someone with moonflower plants. At the time I had just dug up my potatoes and had free space so....(listen to me pretend I need an excuse to buy plants). As you can guess from their name, moonflowers only open at night.
I took the picture on the left at dusk, and I took the on eon the right in the dark using a long exposure. In small quantities I don't think you get the full effect, but if you had a nice large planting and a full moon they would be spectacular.