They really do look like iris. The rhizomes look right. It isn't dutch iris - they have thinner leaves. I am leaning toward Japanese/Louisiana, possibly Siberian. They don't have fans so I really doubt they are bearded iris. Do their roots grow on top of one another? That is typical of the Japanese iris.
If they are Japanese or Louisiana iris, they often take a couple of years to bloom. Was everything newly planted when you moved in? The clumps don't look too large, so I don't think they have been in the ground very long. The little single shoots outside the clump are sort of typical too of these types of iris. Some species cross iris look like that too though, so it is tough to be totally sure until they bloom.
These type of iris are fine under pine straw. Make sure you give them some fertilizer like 10-10-10 now, and a month before bloom time. Do not use anything high in lime near them because that is poisonous to Japanese iris, which haven't been ruled out.
