I bought a tree peony and planted it in a pot on May 31st, but it seems to almost stop growing after the first 5~6 days. The first several days it was really fast and made small new leaves. After that, the whole plant seems stopped growing with some newly sprouted tiny leaves drying out (which is not surprising, they never seemed viable). Could it be because the weather getting hot? The growth stop seemed to coincide with the temperature getting over 80 degrees. Other than that, the plant does not seem to have any problems with the larger leaves but just not making progress. The best thing I can expect is it's growing roots, which I am not confident about. I think it surely has a shock since it planted in such a late time. I am in zone 6a.

@magnolialover I saw Tracey mentioned Superthrive in another post. Is it safe to use with a newly transplanted tree peony? Maybe it helps to improve things in my case?

The pics were taken upon receiving, Day 6 and Day 14.

@peonyplan Superthrive works wonderfully in transplanting. I literally use it on every new planting and water with it once a week while the root system gets established. It isn't all that expensive and a drop is all that is needed. A little bit goes a long way and I could see a difference when I started using it.

Your peony will be much happier once planted in the ground at a nice deep level. Peonies in pots are very tricky and I don't think the root system is all that happy there in a pot.

Yes, why in pot and indoor? Shade outside - may be temporary and plant it as deep as possible in a bigger pot at least. I feel that you still have 5-6 inches of soil to play around.