Peony Dahlia 'Bishop of York'

during last summers midseason malaise; I noticed this variety happily flowering at Rutgers Gardens; decided to try my hand at it and or...Read Moredered several from Plant Delights Nursery; healthy plants; and even though it was almost midsummer; they flourished and flowered in my garden; In August 2012 I traveled to Denver and also noticed some growing happily in a privategarden there and returned to N.J. to find mine still in bloom; continuous until frost
this year they were slow to emerge ( 2nd week of June ) but grew vigorously after then; but were very slow to develop buds; which weren't strong; on attempting to open one lost all it's petals except one; a pathetic site; still a vigorous plant ; just not at all floriferous.
so I'm wondering what happened; since the plants seemed healthy I was hesitant to do anything; but perhaps an application of phosphorous rich fertilizer ?
It would be nice to consider these as the dependable garden workhorses as echinaceas do in midsummer