Linen Heidi! I've already gotten so much use out of this dress it's ridiculous. I was thinking about replacing the pleats with piped princess seams but I knew I needed to keep thing simple. As it is, the piping that I did add was pretty time comsuming but turned out well. I used posts from Diary of a Sewing Fanatic and Pattern, Scisors, Cloth to help make the piping happen.
The dress is 100% linen with a cotton gauze lining because there's nothing I hate more than I slippery lining in the summer time.