Should be fine but toss a sheet or light blanket over the plant if you want. You can try and tent the blanket if the buds are right on the top. We are supposed to have snow tomorrow with lows in the 20's.

I keep several cheep ugly sheets that I have bought at garage sales just for this use. Also use them not for the peonies but other plants for the first couple of frosts and freezes during the autumn.

Thanks for your reply! I didn't cover it last night, but I think I got lucky, doesn't look like there was frost, quite a bit of air movement. Tonight will be a different story though, supposed to get really cold tonight. I did intend to cover it, but got busy & forgot all about it. At least I can cover it, my fruit trees & lilacs will just have to risk it :(