Perennial plants die back during fall and winter months, and bloom again during spring and summer months. USDA hardiness zone 6 runs across the United States, ranging from eastern Washington, down into northern Texas and then up into Maine. Gardeners living in USDA hardiness zone 6 need to plant perennials that can survive both very cold and warm weather. The average coldest winter temperatures in this zone range from zero to -10 degrees F.
The balloon flower (Platycodon grandiflorus) is a clump-forming perennial that earned its name because the flower buds puff up like little balloons. The buds eventually burst open into bell-shaped, violet-blue flowers that bloom from June through August. Hardy in USDA zones 3 to 8, these plants are native to the meadows and slopes of Asia. Balloon flowers typically grow to between 1 and 2 1/2 feet in height. These perennials grow best in fully sunny to partly shady locations. Balloon flowers are commonly used as edging, container and rock garden plants.
Purple coneflowers (Echinacea purpurea) are herbaceous perennials that thrive in USDA zones 3 to 8. Members of the Asteraceae family, these daisy-like flowers have purplish-pink petals that surround orange center cones. These plants have a long bloom period from June through August. The rigid stems can reach up to 5 feet tall. Purple coneflowers grow best in fully sunny locations and tolerate dry, hot and humid conditions. Gardeners usually plant purple coneflowers in mass as borders and in wildflower gardens.
Threadleaf Giant Hyssop
Threadleaf giant hyssop plants (Agastache rupestris), sometimes called sunset hyssops or licorice hyssops, are natives of the mountains of New Mexico and Arizona. These woody perennials grow from 18 to 24 inches tall in garden settings. The small, orange, tube-shaped blossoms typically bloom from July through August. This member of the mint family (Lamiaceae) features aromatic foliage with leaves sometimes used to make teas. Threadleaf giant hyssops are drought-tolerant plants that can grow in poor soils. This plant is often grown in butterfly gardens and rock gardens.
Despite its name, English lavender (Lavandula angustifolia) is actually indigenous to the Mediterranean region. This semi-woody perennial bears highly aromatic flowers and foliage that are commonly used to make potpourris and sachets. Hardy in USDA zones 5 to 8, this lavender grows well in alkaline soil in fully sunny locations. The purple flowers bloom from late spring to early summer. English lavender is often grown in herb gardens, scented gardens and rock gardens.
Red Hot Poker
The red hot poker plant (Kniphofia uvaria), often called a torch lily, is a clump-forming perennial of the lily family (Liliaceae). Native to southern Africa, this plant thrives in USDA zones 5 to 9. The red hot poker features red buds and new flowers that typically mature to a green-yellow color. This plant grows up to 2 feet tall and has blue-green, sword-like leaves that reach 3 feet long. The drooping, tubular flowers bloom in May and June. Gardeners in zone 6 should protect the crowns from winter weather by mulching the soil around the plant and tying the leaves together. Red hot pokers are typically planted in masses as border plants.
Russian sage (Perovskia atriplicifolia) is a woody perennial in the mint family (Lamiaceae) that is native to western China and the Himalayan regions. This sage usually grows from 2 to 4 feet high and features aromatic, greenish-gray leaves. The tubular, lavender or light blue blossoms bloom from July through October. Hardy in USDA zones 5 to 9, Russian sage does best in fully sunny locations. This plant contrasts well with yellow and pink perennials in flower beds.