Whether you grow them from seed or purchase plants, Oriental poppies prefer moderately rich soil with good drainage; avoid damp areas. Allow at least a foot between poppies and other plants. Generally they prefer full or partial sunshine, although some shade is necessary for purple-toned Orientals, which turn a liver-like colour in full sun.
Plant 'em in pots
Potted perennial poppies can be planted spring or summer, but a wider choice is available from mail-order nurseries, which usually ship bare-root plants in the fall. Sink the crown two or three inches (five to seven centimetres) below the surface of the soil. Water regularly for the first few weeks—the roots need moisture while they're getting established and before the soil freezes.
Start 'em from seeds
To grow perennial varieties from seed, follow Twomey's technique for starting annual poppies, and give them a dose of root fertilizer such as 10-52-17 after they germinate. Like annuals, they should go outside when they're just three or four inches tall. Depending on the weather, they usually bloom the first year.
After blooming, let the leaves of perennial poppies die back on their own-the health of the plant depends on it. To disguise the gaping holes left in a perennial border once the leaves are gone, plant dahlias, Michaelmas daisies, daylilies or purple coneflowers nearby.
Orientals are hardy to Zone 3—although plants in Zone 2 can usually make it through the winter if protected by consistent snowcover or a straw mulch under and around (but not on top of) the rosette of new growth that appears in the fall. This prevents freeze/thaw cycles in the late winter, which can be damaging. "Water plants well in the fall. If the ground is really soaked, it'll freeze like a block and never really dry out until the final thaw," Twomey says.
Divide plants every five years to keep them vigorous; late summer or early fall is best because they flower early in the season. Carefully dig up the plant without snapping the roots, and vertically split the mass of shoots into several divisions, making sure each has a bit of the grown and as many roots as possible. Position the divisions a foot from other plants and place the crowns two inches (five centimetres) below the surface. Water well for the first few weeks.
* Read about annual poppies.