The Right Place
Oriental poppies grow throughout most of the United States and into Canada (zones 3). They prefer areas where summers are cool. They tolerate winter temperatures as low as -20°F. Because they need fairly cold winter temperatures and dislike hot, humid summers, they won't grow further south than northern Florida (zone 9).
Planting Nursery Stock
Plant Oriental poppy seedlings in late summer or early fall. In cool climates, they thrive in full sun, but where summers are hot, give them afternoon shade. Plant them in groups of three, spacing plants 1 1/2 to 3 feet apart. These poppies do not always transplant easily. Most failures are due to planting seedlings too shallowly. When setting the plants in their holes, be sure their crowns, the thick place where the foliage joins the roots, are about 3 inches below the soil surface. Oriental poppies do best in light, sandy soil with good drainage and lots of humus (such as chopped leaves, peat moss,) mixed in to at least 18 inches deep. The soil should be slightly acid (pH 6.5). Once poppies are established, do not disturb them.