Even though winter temperatures can drop to -25 degrees Fahrenheit, gardeners in USDA zone 4 have a variety of hardy, brightly colored perennial flowers which they can successfully grow in their gardens year after year. Although many perennials reliably survive extreme winter temperatures, you can ensure their survival by covering them with a protective winter mulch (a 6-to-12-inch layer of hay, straw or leaves). Remove the mulch in early spring.
Native to the North American arctic regions, Iceland poppy (Papaver nudicaule) is a hardy perennial that grows 12 to 24 inches high. It produces the same type of papery-looking, single flowers as larger-growing poppy varieties--but has a longer blooming period. Iceland poppies bloom from May through July from seeds planted either in early spring or the previous fall. Sow seeds on the surface of the soil and gently press in with your hands. Cover the area with hay or fallen leaves for the winter months and remove this protective mulch in early spring, before the ground is fully thawed. Iceland poppies produce orange, yellow and white flowers followed by the trademark poppy seed pods, which can be dried and added to dried arrangements. Planted en masse in a single color, Iceland poppies produce a dazzling splash of color. They are hardy through USDA zone 2.
Also called perennial larkspur, the delphinium plant (Delphinium elatum spp.) comes primarily with blue flowers, but also has lavender, purple, pink, orange, scarlet, yellow and apricot flowers. Many flowers have a white or black center, called a "bee." Delphinum elatum grow up to 6 feet high and produce tall spikes of small individual flowers that open from the bottom up along their spiky stems. It's best to grow delphinium in full sun and moist, well-drained soil. The plants don't do well in soils low in pH; they prefer neutral to slightly alkaline soil. Feed with 10-10-10 fertilizer when planting and again when the flowers begin to bloom. Delphinium are heavy feeders and will benefit from a mulch of partially decomposed compost or well-rotted manure. Plants may need to be staked because of their height. Position tall stakes near the plants when setting them out in early spring. Most varieties of delphinium are hardy through USDA zone 4 with winter protection.
True garden lilies (Lilium spp.) are available in all shades of many colors--such as red, yellow, orange and pink. They bloom anytime from early June through September, depending on the variety. Plant lily bulbs in autumn or early spring. They grow about 36 inches high with a stiff stem and strap-like leaves that grow all along the stem. At the terminal end they form large showy flowers. Many varieties of lilies have very fragrant blossoms. It's best to water your lilies as needed to keep their soil from drying out and to mulch the soil to discourage weeds from growing. Lilies will happily grow and bloom for five years or longer before they need to be dug up and divided. Lilies are hardy and will survive winter without protection through USDA zone 4.