I was somewhat surprised to see in Adelman's planting instructions that peonies should be planted with roots horizontal. I always leaned towards planting roots vertically.

Is that for tree peonies? I don't feel so bad now, I don't have the depth and I had to plant them horizontally.

I always plant mine vertically.

These are the generic directions for all peonies. "Lay the root in the prepared hole horizontally with most of the eyes (what will become the new stems) pointed upward. Ones not pointed upwards will reorient themselves towards the sun." However, the tree peonies in particular that I got had strong vertical roots and eyes. I couldn't see bending the roots that much.

I've seen it recommended by big growers to plant horizontally, say it encourages vigorous root growth. Know it's recommended for planting blind roots as eyes can pop out really anywhere along the length. I typically plant mine however it's easiest to get the majority of eyes best positioned to be about the same distance from the surface. If I get a root that is basically one long storage root with eyes at the tip I almost always plant it horizontally—there are some roots that just seem to push for that positioning because of their shape. Those that arrive with more of a connective crown with a few feeder roots I typically plant vertically.

I always plants roots at an angle with eyes pointing up as even as possible.

Adelman's also has a planting video that shows planting basically at soil level and mounding over them. With their zone and the amount of rain they get they can get away with things that colder and drier areas can't.

I have a question on planting if anyone can answer. I spur of the moment purchased a peony this fall. Unfortunately it's on back order and now the shipping estimation is November 20th. I'm in zone 7a Philadelphia. Is that too late to plant outside. What is the best way to deal with receiving a peony so late in the planting season.

I read that as long as the soil is not too hard to work, you can plant.
Some pre dig and keep the planned backfill soil somewhere it won't freeze.
Others cover the area with plastic sheeting.

A video is available on the Facebook of APS group, probably related to this planting method:
https://www.facebook.com/75545...

Ruthanna, I am zone 7a, too. I am still planting.
The most important thing to remember is to make sure that no water pools over the newly planted roots. I make little mounds of soil over mine that I wash away in the Spring after the stems start emerging.
Good luck!

I am in zone 5, and I am still planting