I currently have Pumilla Dogwood, Itea, Witchhazel, Birch, Black Walnut, Ninebark and a native blue Iris, maybe virginia?.
I tried Aronia & a variegated dogwood, but a local critter kept chewing them down to a stub so I moved them into our fenced yard.
Also tried Pussy Willow but it died. I had it in a spot that alternates between flooded & bone-dry, and at the drip-line of a Black Walnut tree - not sure why it died.
Tried acorus/Sweet Flag, but it got so huge very fast, and didn't bloom so I removed it.

If you fertilize your lawn, try very hard not to get the fertilizer anywhere near standing water - the nitrogen will cause algae bloom, and you'll have green water & rocks which the birds & ducks will avoid. (I've got maybe 4 sq. ft area that rarely drains completely, and there's 2 ducks that both squeeze themselves into the water, so we call this 'ditch' the 'duck pond'.) Later in the summer when it dries out, everything will then be covered w/ dead algae brown crust.

And if you see a cattail growing, don't say "Oh cool! It's a cattail!" - Remove it immediately or you'll be sorry... like I was.

Hope this helps! Good luck!

I put a grey birch and american hazelnut in my raingarden. Both are native to the Midwest and can tolerate wet and variable conditions. You might just Google "rain garden" and "plant list" to see what you find - I found some links from Wisconsin DNR and there are other Midwest community projects going up all the time. Good luck!

Thanks for all those suggestions. I have googled but wanted personal experience - like the tip about the cattails! The Ninebark surprises me - they can tolerate standing water? The water isn't standing long enough to grow algae (unless we keep getting these torrential rains). It lasts a day or so, maybe puddles longer in a few spots but largely drains in 24 - 48 hours as long as the ground is thawed. A garden center last year suggested Japanese anemone so I bought several and planted them about mid summer when we generally don't have standing water anymore - they did well then, but not one came back - expensive and aggravating.

The Ninebark isn't in a low spot. It's up higher on a slope where it gets flooded maybe 2 - 3 times a year. Otherwise it's dry cuz rain water just runs off. This is the 2nd summer it's been in this spot, and had it's roots submerged 2 times, for no longer than 6 hours.
Alot of this area looks bone-dry most of the summer. There's alot of clay, and the top layer gets cracked & dead-looking, but when I dig down past 8" I find very moist clay.