Purple Peony Papaver somniferum. Purple Peony poppies feature wonderful, fully double, tightly packed petals that result in a very striking appearance. The dramatic, peony-shaped flowers only open for one day, but appear from July through September. They can grow to 10cm (4") across. The dried seed heads are highly ornamental, and the edible seeds can be used in baking. Purple Peony poppies are highly attractive to bees, but resistant to grazing deer. Expected plant height to 90cm (36"). Annual.