If you plant some of the best from every category of Iris - you will have them blooming from earliest spring (the first real color along with the Hellebores)
through to high summer with the crescendo of the delioursly beautiful Japanese Iris ensata...the more delicate 'beardless' variety that often have face-up sometimes filigreed-looking 6" diameter flowers... (see the first picture). All those big blowsy bearded ones are inbetween. They are my least favorite but they do come in glorious color combinations (see the mixed bunch).
But those to order right now and plant along with your tulips and daffodils, are these incredibly sweet and small early Iris. Sometimes they are referred to as Dwarf Iris and other times Rock Garden Iris; but whatever you call them they create a great buzz of heartwarming excitement when they come peeking out of the ground --- planted around snowdrops they are really the perfect counterpoint. Even peeping out from under this Deer-Away stained Yew, they give that magic resilience...though usually classified as Iris reticulata, there are a few other species (they are always classified together in the catalogues). This dreamy pale blue-green one is Iris histrioides Katherine Hodgkin. They come in an amazing range of colors, the blues alone are described as sky, flax, bluebird, lobelia, blackish and so on. The secret is to plant lots of them and not in one big clump....the bulbs are small and you can go about digging little holes everywhere so they will spring up unexpectedly all over the place.
Brentandbeckysbulbs.com have a wonderful selction with good pictures....but if you are willing to get into a little quantity - then vanengelen.com has more than a dozen to choose from at prices a fraction of the others.