Most northern gardeners are doubtless well acquainted with the idea of plant hardiness, but actually finding plants which will survive the difficult winters of the upper reaches of the Northern Hemisphere can be a tricky proposition. Even so-called hardy chrysanthemums frequently have trouble making it through a Zone 5 winter; many plant developers label perennials as hardy, though they likely were never given adequate overwintering trials in the upper Great Plains or Alaskan growing zones.
Arctic Lupine (Lupinus arcticus)
This beautiful Alaskan native can survive winters with average lows of minus 30 degrees Fahrenheit, making it spectacularly hardy. Like other lupines, this plant prefers sunny, rocky to sandy or otherwise well-drained soils though it will not tolerate drought conditions. Butterflies love the lupine, which can grow up to 1 foot in height.
Blue Flax (Linum perenne)
Though not the type of flax used for linseed oil and linen fiber production, blue flax is nonetheless a very attractive garden plant. Plants grow in clusters 6 inches across and produce sky-blue flowers in the spring and then again in the fall. Good for borders or rock gardens. Blue flax is native to Alaska.
Bunchberry (Cornus canadensis)
This perennial woodland ground cover has many of the same characteristics of its cousins, the dogwood trees, including oval-shaped, pointed leaves and green flowers surrounded by creamy white petals, or bracts. Flower clusters develop into bunches of bright red berries, which give the plant its common name. Plants grow to 6 inches tall and spread via underground rhizomes.
Fleabane (Erigeron glabellus)
A member of the aster family, this northern native plant produces loose clusters of daisy-like flowers with yellow centers and dozens of white to pink outer petals. Plants grow up to 20 inches tall in full sun; after blooming, fluffy white seedheads form.
Goldenrod (Solidago multiradiata)
A smaller member of the goldenrod family, this yellow-flowered perennial grows no larger than 2 feet in height, producing larger-than-average clusters of ray-type flowers in late summer and early fall. Plants prefer partly shady sites in dry, rocky soils. This goldenrod attracts butterflies and is the preferred larval host plant for the Damoetas Checkerspot butterfly.
Great Burnet (Sanguisorba officinalis)
Another native of Alaska and the upper reaches of the Northern Hemisphere, great burnet is a wildflower which spreads via rhizomes and self re-seeding; dark red pine-cone shaped flowers appear in the summer. While the flowers are interesting, the plant is mainly valuable for its use as an edible plant: young leaves make a good addition to soups and salads.
Harlequin Flower (Corydalis sempervirens)
The foliage of this northern native strongly resembles that of bleeding heart (Dicentra species), and the dangling pink-and-yellow flowers which appear on stalks in the plant's second year also somewhat resemble the flowers of the bleeding heart as well. Cordalis prefers dry, rocky soils in partly shaded locations, growing to between 1 and 2 feet tall.
Joe-Pye Weed (Eupatorium maculatum)
One of the most spectacular native marshland plants, Joe-Pye Weed can grow to between 6 and 10 feet tall, bearing clusters of purple flowers that attract huge numbers of bees, butterflies and hummingbirds. Hardy to Zone 3.
Marsh Mallow (Althaea officinalis)
This native wetland plant was used by northern Plains Indians as medicine to relieve sprains, bruises, coughs and ailments of the urinary tract. Large pink to white flowers appear at leaf junctures along the stem, giving it a hollyhock-like appearance. Hardy to Zone 3.
Marsh Marigold (Caltha palustris)
This bright yellow springtime bloomer grows to roughly 1 foot tall and prefers moist, sunny locations. It is one of the first flowers to appear in spring in its native range. Plants are known to overwinter well through USDA Zone 3.