Outsidepride Peony Double Flower Seed Mix - 5000 Seeds Peony poppies are annual flowers growing in USDA Zones 3 - 8. This poppy flower seed mix grows to 32 - 40 inches in height. These large Peony Poppy flowers are 4 inches across and form on long, sturdy stems. These flowers will make your garden look great, and cut them often to enjoy beautiful arrangements for indoors! Sow 4 - 5 peony poppy seeds per plant.