When cold snaps threaten, wise gardeners stay toasty inside, confident their cold-tolerant perennials can shrug off low temperatures. Every garden has its cold spots, such as low, damp, shady hollows and open, exposed areas that may be sunny and dry during summer. Choose plants well-suited to growing conditions to give them the best chance of surviving winter. In spring, leave plants that seem damaged by frost, or even dead, until warmer weather returns before taking any action, as damage can look worse than it is.
Hardiest of its kind, grape leaf anemone (Anemone tomentosa "Robustissima") is a fall-blooming perennial suitable for U.S. Department of Agriculture plant hardiness zones 4 to 8. This tough plant grows happily in full shade and provides prolific silvery-pink flowers, growing up to 36 inches tall and 24 inches wide. Auslese lady's mantle (Alchemilla mollis ''Auslese'') is another shade-loving perennial that tolerates cold temperatures. This plant works well as ground cover, growing 12 inches tall and 12 to 18 inches wide, and is suitable for USDA zones 3 to 8. During summer it's covered in bright, lime-green sprays of flowers.
A cold-tolerant perennial that loves full sun, Ozark sundrops (Oenothera missouriensis) is hardy in USDA zones 4 to 8. Its 4-inch, lemon-yellow flowers appear throughout summer above glossy, lance-shaped green leaves. Ozark sundrops also tolerate drought. "Winky Red & White" columbine (Aquilegia caerulea ''Winky Red & White'') grows happily in USDA zones 3 to 8 in full sun, surviving winter temperatures by dying back in fall. Producing pretty red and white spring flowers attractive to butterflies and hummingbirds, this plant grows 12 to 15 inches tall and wide.
Tolerating cold and drought, hairy bergenia (Bergenia cillata) is named after its large, hairy burgundy leaves. Suitable for USDA zones 5 to 8, this deer-tolerant perennial prefers part shade and grows 1 foot tall and 1 to 2 feet wide. From spring to early summer, it bears white or pale pink flowers on 10-inch-long stems. Another cold-tolerant perennial with interesting foliage, fish-scale sedum (Sedum tetractinum) grows best in USDA zones 4 to 8, its rounded, overlapping, evergreen leaves turning reddish-bronze in fall. A useful, drought-tolerant ground cover plant, fish-scale sedum also provides spikes of bright yellow, summer flowers.
Wet ground can be especially challenging in cold temperatures when plants are dormant and not drawing moisture from the soil. Bistort (Persicaria amplexicaulis) copes with cold, wet conditions well, growing best in USDA zones 4 to 8. A spreading but non-invasive perennial, bistort grows 3 to 6 feet tall and wide, and provides white, bright red or purple flowers on long stalks from early summer to fall. Tolerating even colder temperatures, Japanese iris (Iris ensata) is suitable for USDA zones 3 to 9. Loving wet feet, Japanese iris delights with its red-purple or purple, 6- to 12-inch-wide summer blooms.
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