Perennial Flowers for Cold Climates

USDA Zone 2

Minimum winter readings in USDA zone 2 are between 40 and 50 below zero. Such cold does not daunt the growth of hollyhock (Alcea rosea), a short-lived perennial often located in cottage gardens. Hollyhock grows to 8 feet, needing protection from zone 2 winds, so plant it near fences or against buildings, advises the Washington State University Clark County Extension. "Nigra" is a cultivar for zone 2 featuring maroon flowers so dark that they look to be black from a distance. Hemerocallis "Song Sparrow" is a daylily cultivar for zone 2, generating brown flowers as wide as 5 inches for your perennial borders. Consider using Arctic poppies (Papaver nudicaule) and common fleabane (Erigeron philadelphicus) as flowering perennials in zone 2 as well.

In USDA zone 3, where it can reach 40 below zero in a cruel winter, lady's mantle (Alchemilla mollis) is a possibility as a perennial ground cover. The yellow-green flowers of May are just part of this plant's appeal, as the large, light green leaves, 6 inches in diameter, glisten with water droplets after a rainstorm. Lady's mantle grows to 2 feet high and creates so many seeds that it can cover a small area. Echinacea purpurea "Sir Lancelot" is a purple coneflower cultivar for rock gardens and the front of a zone 3 perennial border, growing to 32 inches and producing pink flowers all summer long. Among the many hostas for zone 3 are cultivars including "Janet," "King Tut" and "Guacamole."

Thirty below zero is about as cold as it will get in USDA zone 4, which happens to be the most frigid zone a New York aster (Aster novi-belgi) grows in. This perennial turns out attractive purple-rayed flowers in September, growing to 2 feet tall. Cut the plant to the ground after it finishes flowering and watch it pop back up the next year. Fragrant, red hollow stems are a feature of hemp agrimony (Eupatorium cannabinum), a perennial for zone 4 attractive to butterflies and hummingbirds. Its pink flowers bloom in August, with the plant preferring damp areas. The fruit and leaves of pokeweed (Phytolacca Americana) are not edible for humans, being toxic, but birds eat the purple-black fruits which develop from the summer's green-white flowers. Capable of growing 10 feet in one growing season, pokeweed always dies to the ground in late fall.

Twenty below zero is not unheard of in USDA zone 5. Locate bear's breeches (Acanthus spinosus) in your perennial borders within this zone. It features pink to mauve flowers arranged in vertical rows on flower spikes. Bear's breeches grow to 4 feet tall. Campanula "Kent Belle" generates a beautiful drooping violet-blue flower resembling a small bell. This cultivar needs some shade in the summer and it blooms during June and July. Sweet William (Dianthus barbatus) and nepeta (Nepeta racemosa) are two more perennials for use in zone 5.