I'm a new gardner, but I noticed nobody has responded. I live on the zone 5/4 border, and many gardners here plant for zone 4, so we're colder than you. I planted my new peonies with the tops exposed, and my local nursery said they wouldn't need mulch. Since peonies are susceptible to rotting if they get too wet and because they are so hardy, they said that the tops can be left exposed. In fact, they very strongly recommended it. So, if they're right, then you won't need the mulch. I don't know for sure, but it seems to me that once the peony is established and grown it pretty much doesn't die, so the mulch issue isn't a big one. Since we expect to get vere healthy snow cover this year (yea!) and wetness can be a problem, I feel better not having the mulch on them.

P.S. As I was previewing this messsage my kids began to scream because our first snowfall has just begun right now!

@deanna Thank you for responding! I ended up raising my rhizomes because I was worried. But they are still covered in mulch. I have huge beds that are completely covered in mulch. I guess I could move the mulch off the areas where I planted the peonies.

Thanks again!

Nobody that I know of has explained why a peony acts the way it does if its depth is more than the 1 1/2" to 2" the eyes are put below surface.....but it is a fact of life.
Too deep, a peony may never bloom.
Put it down to ....that's the way it is...for that plant, no more than 2" the crown is placed below soil surface.

Putting mulch over the crown to me, is much like putting soil over it....so I make sure not to do it.
The foliage is cut down anyway....so any amending of the soil I make sure is done in a side-dressing mode only.
Compost, with or without, added well composted manure is appreciated by peony.
But, it doesn't like sitting in wet soil.....good drainage is important. Compost can help a plant's planting hole retain moisture....so that may add a moisture level that should be looked at.
For winter mulching, I use evergreen boughs. It acts as a good insulator for when the snows come. It can keep the soil from heaving during spring thaws.

I agree with Jeannie. I don't think I would put any mulch over the peonies, just your 2" of dirt. Peonies can be pretty tough plants, as long as you don't bury them too deeply. We inherited some with our farm and they get no winter protection (and temperatures can get as low as -27 F) and they bloom beautifully each year. They're the white peonies with the burgandy edges..very pretty :)

This year we found some burgandy ones coming up in back of the old farmhouse that were probably planted at least thirty years ago.

To mulch or not to mulch depends on your soil rather than the depth of your planting. If you have a problem with plants heaving out of the ground because of the freeze/thaw action of the soil you should mulch until the the plant has time to root. You should remove any mulch from the crown area when the buds start to emerge from the dirt. You can rake the remainder of the mulch and remove or leave it.

If you look at many peony pictures many will have a mulch of leaves in the background. I will place some on newly planted peonies but allow the leaves to remain where they land rather than raking and removing on established plants. Because my leaves will decompose to a thin layer and we have heavy 4-6 inch rains any extra mulch is washed off the buds and for me causes no problem. If I wish to have them decompose quicker I sprinkle common sugar on the leaves.

As I understand the frost heaving, doesn't a thick layer of snow do much to prevent that? From what I understand, this winter should be a nice snowy one. I am brand new to gardening in snow (actually new to gardening in general, but I've always lived in a very temperate climate until now), but I was thinking that if we get generous snowfall that stays through most of the winter then my plants should be protected and insulated. Is that correct?

Last winter our snowcover didn't disappear until spring thaw. Very nice! I just considered it to be pretty. But now it seems that it was also healthy.

Thanks for your post on heaving. I wouldn't have thought of that with the peonies!

Snow will do the same thing as long as it is there. Since no one can guarantee what Mother Nature will do it is best to help her. Last two years places that normally are snow covered most of the winter, think western ski areas did not receive snow until late in the season, February. I just returned from Minnesota and this weekend from Minneapolis South had several inches of snow. I was told that it normally does not snow that much until mid-November.

Talk to your neighbors about your areas normal weather. Last year was strange all over. Good way to meet your neighbors if you are not friends already. Side effect of talking to neighbors is sometimes when they split their plants they will think of you when they have extras. A very good plus when plants are involved.