Question
growing in afternoon sun only. should it flower spring-summer.

Answer
Peonies bloom in the spring, my friend.  Paeonia lactiflora 'Dr Alexander Fleming' (aka P. sinensis) is an herbaceous Japanese Peony.  They are slow growing and take time to establish.  Biggest mistake people make with these is planting them too deep, delaying bloom.  Make sure yours has full sun and is not planted more than 2 inches below the soil line.  1 to 1-1/2 inches is even better.