they need to be potted up. I find they do better in a free draining soil based compost like a john Innes. Not a peat based one. The rhizome needs to be on the surface [1/2 buried] so they get baked by the sun.

See what Siris suggests, she grows lots and is more knowledgeable than me.

Yes get them out of the garage, wash them off real good and plant them. They are very adaptable to different types of soil as long as they have good drainage. Average potting soil is fine. When you plant them, don't bury them entirely. Let the rhizomes sit on the surface with only the roots buried. The rhizomes must be exposed to the sun in order for it to flower. Your irises didn't flower because they weren't mature enough or they were shaded from the sun - buried too deeply or under a bush/tree perhaps. Find a sunny place for them to live. The sun hitting the rhizome is what triggers it to flower as mentioned above. They might take a couple years to flower.