The foliage on evergreen perennials remains intact despite frigid weather. So, for the most reliably frost-resistant perennials, choose evergreens suited to sub-zero temperatures. Perennials for U.S. Department of Agriculture plant hardiness zone 2 can survive temperatures down to minus 50 degrees Fahrenheit; perennials for zone 3 can survive temperatures down to minus 40 degrees Fahrenheit; and perennials for zone 4 can survive down to minus 30 degrees Fahrenheit.
1. Pretty Winter Flowers
Perk-up your barren winter landscape with evergreen perennials bearing pretty, winter flowers. Incredibly hardy, early bergenia (Bergenia crassifolia) bear magenta-pink flowers from mid-winter to mid spring in any USDA zone. Ideal as an edging or mass planting, it grows 12 to 23 inches tall. Hybrid hellbore “Double Fashion” (Helleborus Nigercors "Double Fashion") bears white double blossoms from early winter to late spring in USDA zones 4 through 9. Excellent for full to partial shade, it grows 12 to 16 inches tall.
2. Extremely Hardy
Some evergreen perennials are extremely hardy and laugh in the face of frosty weather. Golden nugget ice plant (Delosperma congestum) prefers sandy soil in partial shade and puts out yellow flowers from late spring into early fall. An easy way to beautify unsightly gravel screes, it grows 2 to 3 inches tall in USDA zones 4 through 9. Dwarf orange geum “Werner Arends” (Geum “Werner Arends”) puts out bright-orange flowers from late spring to early summer and deadheading encourages continuing blossoms. It grows 12 to 16 inches tall in USDA zones 2 through 9.
3. Go Ahead, Step On It
These evergreen foot traffic-friendly perennials are so frost-resistant, you can grow them in USDA zones 1 through 9. Pink pussy-toes “Rubra” (Antennaria dioica “Rubra”) is a drought-tolerant perennial displaying deep-pink flowers in late spring to early summer and takes a moderate amount of trampling. Perfect between paving stones and on rock walls, it grows 4 to 6 inches tall. A northern Canada native, arctic phlox (Phlox Borealis) shrugs-off light foot traffic. This drought-tolerant plant displays a carpet of hot-pink flowers from mid- to late spring, grows 2 to 4 inches tall and is just the right choice for rock gardens.
4. Native Ferns for Shade
If you’re looking for reliable and easy perennials to fill a shady space with moist soil, you can’t go wrong with Christmas fern (Polystichum acrostichoides) and leather wood fern (Dryopteris marginalis). An eastern U.S. native, Christmas fern thrives despite hot and humid summers, and grows 12 to 23 inches tall in USDA zones 3 through 9. A northeastern U.S. native, Leather wood fern performs best when cut back in late winter and grows 18 to 23 inches tall in USDA zones 2 through 9. Both native ferns are evergreen in most climates.