Well, I can give you my experience with some boxed peonies. I've never dug any up, but I have planted them in the spring, they come up quite small, & have appeared to die completely. They still came up the following spring, bigger. Often it was the 3rd year before I actually got bloom from them. You are in an apartment, I assume you were growing it in a pot? Not impossible, but I would have a hard time because I tend to overwater plants in a pot. Still, not a very rewarding plant when you would have to wait so long to get bloom. Peonies can be very rewarding & beautiful plants, but for an apartment dweller, maybe dahlias would be a better choice?

bpeterson, that root is still several years away from flowering, sorry. If you live in a fairly warm zone a peony might make it through the winter in a pot, think the warmest I've seen people post about potted peonies has been zone 6. If you want to try it I'd replant and just leave it alone, pulling it out of the soil breaks off the little hairlike roots and sets it back further. Like Nancy said peonies are pretty hard to grow in pots, I'd experiment with your root by replanting it in a large pot just so it doesn't have to be moved if it survives since it'll get quite large. If it comes back and increases you might want to double pot it to insulate the roots from summer heat. By this I mean plant it in one of the black nursery pots then put that pot inside a bigger ceramic or similar pot big enough so the sides don't touch. You can put moss or some biodegradable mulch over the soil if you don't want to see the ugly pot but keep it away from the stems--mulch that stays wet could cause rot damage to it. Make sure to water only when it's dry at least down an inch or so--too much water is just as dangerous as too little so make sure your pot(s) drain well. Peonies want full sun but the roots will get overheated quickly in a pot, if you can shade the pot somehow while allowing the growth to get sun that would be your best bet. If you can keep this one alive and it prospers I'd think I'd reward myself by purchasing a 2nd one from a nursery that already has buds so you can have blooms next spring. If you wait for the one you have to bloom I think it'd be at least 3-4 years, sorry.

Thanks guys I ended up dipping it in kelpmax / water solution and potting it again. So sign of growth

You need to read about peonies. There should be no growth until next spring. If you replanted in the plastic pot shown in your other post you probably have killed it.

Plastic pots do tend to heat up more than peonies appreciate in the summer, you can negate that aspect by putting the whole thing into a larger terra cotta or heavy clay pot for insulation. If you can find a spot where the plant gets sun for several hours a day but the pot stays in more shade that'd be the best circumstance for growing in a container. Maifleur is correct about seeing no growth now but hopefully you'll see it again in the spring. I know it's tempting to dig things up when they're not growing as fast as you'd want but it's disruptive to root growth---I'd just leave it alone if it grows in the spring. Good luck!

Over many years I have purchased boxes of mini roots from costco, in the spring. Have always potted them up in one gallon pots with well draining mix, and kept in mostly shade through the summer, being careful to keep soil moist. Almost all survived and grew about a foot of foliage. When the rainy season starts in the fall I plant them in the ground, hardly ever losing one.