Do I have to dig them up every year or will they just come back on their own? I know that occasionally I will have to separate them.
Dutch iris will come back on their own every year without extra care from you.
As a child, I called small, very dark blue iris Dutch Iris. You don't have that name listed. Is there another name I might try? Thanks.
Here is a link with information about Dutch Iris.
https://www.gardeningknowhow.com/ornamental/bulbs/iris/planting-dutch-english-and-spanish-irises.htm
I have what I think is Dutch Iris which was given to me by a friend. I have had them for about four years or more and only about two to three bloom. What can I do to make them bloom. Thanks
Dutch Iris can be fickle. They are picky about soil, moisture, temperature and sunlight.
They require a 6 to 9 week cooling period to bloom well.
They also may need to be divided and given a bit more room.
Depending on the variety that you are growing, they may not be as well suited to your growing zone as some others.
Here is a link to refresh you on the care requirements.
https://www.gardeningknowhow.com/ornamental/bulbs/iris/planting-dutch-english-and-spanish-irises.htm
Is it good to cut them back before frost?
It is good to cut the stalks, and the dead growth. It is not necessary to cut the leaves. It will not hurt them, but you should leave them as they will need these to keep roots growing. Here is more information that will help: http://www.clemson.edu/extension/hgic/plants/landscape/flowers/hgic1167.html
You may have too much Nitrogen in the soil.
You can add Phosphorous to the soil; Bone Meal is a great way to amend the soil.
These links will help you.
https://www.gardeningknowhow.com/ornamental/bulbs/iris/iris-plants-not-flowering.htm
https://www.gardeningknowhow.com/ornamental/bulbs/daffodil/daffodils-not-blooming.htm