Shame on Armstrong's for selling herbaceous Peonies. They do not do well in Southern California, except the local mountains (with regular irrigation). They need winter chill to bloom. The foliage may come back, but the plant won't bloom (unless you live in the local mountains) I'd take it back and get an Itoh peony when they show up, instead. What you have there if you are a coastal dweller is intended as an expensive annual.

Itohs do quite well in Southern California. I've had one for four years now and it has bloomed well every year, despite the drought and despite the very warm winters we've had the last few years. Plant it in at least 1/2 day sun, in an area with good drainage, but that stays relatively moist. A thick fluffy mulch will keep the soil cool.

Your plant looks healthy and it is only one plant, do not divide. You may not get enough winter chilling at your location. Check with your local county extension about the number of hours chilling where you are. If you have 400 hours or more you will probably be able to see your peonies bloom in a year or two. When you plant in the ground they should be so you can see the top of the root where the buds form,ALL WINTER. That is the part of the plant that needs the chilling. As it is in the pot is too deep for your location. Soil covering the buds is insulation. Al

(socal zone 9)

I've had pretty good luck with growing peonies. I also got one from Armstrong's (Madame Emile Debatene). MED gets full morning to mid-day sun and afternoon shade. Make sure to keep it moist in the hot dry summer months, and in the winter at night time i would drop ice cubs to cover the top of the plant in an effort to simulate colder temps.. and here is my beautiful bloom today.