I would keep it in the pot until planting time in the fall. I am assuming it is in at least a one gallon pot. It may not bloom next year, but the foliage is attractive. Al

I've planted peonies in the spring before. As a matter of fact, I planted two last year and one is amazingly robust and full of buds now. The other still is young looking.

keep in mind CA is different than MA. Other than the current mini-heat wave we are in, planting and even transplanting is fine during May and often June (with care).