If I had to choose just one type of flower to photograph, the choice would be dahlias. They come in an endless variety of shapes, colors, sizes and petal arrangements.
Made with a 18-200 mm lens with a Canon 500 D closeup attachment (and of course a tripod and my new Markin M20 ball head - solves the "creep" & "fine-adjustment" problems I had with the Kirk BH-3).