Hi there-It could be the depth at which you planted them. Iris don't need a lot of dirt covering them. (Or so my mom always said to me). There is the iris forum on here-did you post this questions there too? They have lots and lots of information over there. Good luck!

You need to verify with a local source that Dutch iris bulbs are hardy in your area.

There is a possibility you had poor bulbs. If they grew in good soil and the leaves were allowed to ripen they may bloom next year. Provided the winter is not too severe.

It's the beardeds that are planted shallowly.

Dutch Iris like limey soil. They like wet winters, but hot, dry summers. They are not particularly picky about clay or sandy soil.

This all sounds simple, but it is not, at least for me. I want them in my mixed borders, but because our summers are so hot and dry, I do alot of irrigation. The irises come up faithfully, but I get almost no blooms.

You are very far north. Iris gal is right. You need to verify that they are winter hardy in your area, though it sounds like they may be, since you are at least getting leaves.

It could be the depth at which you planted them. Iris don't need a lot of dirt covering them. (Or so my mom always said to me).
Indymom's Mom was thinking of bearded iris rhizomes which are totally different than Dutch iris bulbs.

Though sites selling them say they are hardy to zone 5, I have had very poor luck with them, even the first season after planting them, here in zone 5b/6a.

The site below says they should be planted 6" deep and 6" apart.

Here is a link that might be useful: Dutch Iris at John Scheepers

If you bought at the end of the bulb buying season they might take a year or two to settle in.

You could plant under a deciduous tree such as the south side of a fruiting plum where the sun can get them while the leaves are up and the roots help them stay dry over the summer.

I get good flowering from the ones in the 'gravel garden' - and I probably have more rain/lower overall temperatures over summer than you do.

Personally - feed sparingly, if at all. Benign neglect :-).