The United States Department of Agriculture Plant (USDA) Hardiness Zone Map divides the country into growing zones according to average annual minimum winter temperatures. The USDA's map is a good general guide for USDA zone 4; however, using a more specific map and zoning information, like the popular Sunset one, can provide detailed information, making it easier for gardeners to plant and grow in their area.
Translate USDA Zones to Sunset Zones
The USDA map is a great tool if winter low temperature was the only factor affecting the ability of a plant to survive in a particular region. Zones are divided by 10-degree increments. However, numerous other factors come into play within each of the broad zones. These factors include:
- Ocean Influence
The Sunset zones, which have been popularized by Sunset Magazine, are climate zones established by the University of California Cooperative Extension Department. Although USDA zones are widely used, the Sunset zones are more specific and provide a great deal more detail within each growing zone including the factors listed above. According to the Sunset growing map, zone 4 on the USDA map translates to zone A1 on the Sunset Map.
Sunset Zone A1 Characteristics
Zone A1 includes most of the interior of Alaska. This area has long warm days in the summer and a great deal of snow in the winter. Average winter minimums are between -10 and -20 F, while summer highs are in the 70s. The average growing season in this area is around 113 days. Since the soil in this region of Alaska can be very cold and hard to work with, many gardeners use black plastic sheeting and raised beds to warm the soil up before planting. Raised beds also allow you to control the quality of the soil.
Popular Hardy Perennials
Hardy perennials will tolerate the extreme temperatures and live through the cold winters in interior Alaska.
These trailing perennials bloom in spring and are great fillers for rock beds, where they will mound together forming a colorful carpet. Depending on variety, these plants that range in height between 4 and 6 inches, bear red, lilac or lavender flowers. Plant these beauties in well-drained soil and in full sun. Cut back after flowering to promote health.
Shasta daisies are happy plants with a bright yellow center and white petals. Excellent for cut flowers, these summer bloomers form clumps that are 2 feet wide and up to 3 feet tall. Plant these daisies in a site that gets full sun for best results. This low maintenance plant is a favorite of many types of butterflies.
Yarrow is a perennial, somewhat hairy, herb that is native to Europe and Asia. Yarrow will thrive in poor soil and prefers a sunny spot in the garden. Yarrow will grow to 20 inches high on a single stem with rough fern-like leaves and clusters of small white flower heads. This attractive plan blooms in late spring throughout the summer and can be dried to use as a spice with a sage-type taste.
These woodland natives love shade and will do well in filtered or full shade. Beautiful arching heart-shaped pink or white flowers grace this plant with fern-like foliage. If planted in moist soil, the bleeding heart will bloom from early summer until frost. After this plant matures, you can divide it in early spring to make more.
Hardy geraniums are sometimes called cranesbill geraniums because the shape of their seedpods looks similar to a crane's bill. Toothed foliage is very attractive and white, pink, blue, purple or magenta flowers appear to float on top of the leaves. This geranium spreads by rhizomes and will grow to 2 feet tall. Plant in the sun and water during dry periods.
Popular Non-hardy Perennials
It is common in interior Alaska to plant perennials that do not tolerate the extreme cold as annuals. These non-hardy plants are a lovely addition to any summer garden.
Coreopsis is an herb that is related to the sunflower. Plants can grow up to 4 feet tall with beautiful showy yellow flowers with orange centers. This plant is an excellent addition to a wildlife or cutting garden.
There are many varieties of rudbeckia to choose amongst. Many types have yellow or orange flowers with a dark center, but you can also find bronze, russet, and mahogany plants. Daisy-like flowers can be single, semi-double, or double with hairy leaves. Dwarf varieties grow to about 1 foot, while tall varieties reach up to 9 feet.
Annuals live only one year and die. Because they survive only one season, they must be replanted each spring. Many annuals can be started indoors and transplanted outdoors once the weather warms up.
Cosmos are an easy to care for annual that rewards gardeners with silky, daisy-like flowers in a myriad of beautiful colors. These plants are easy to start from seed and do best in full sun. Pinch the spent flowers to encourage lots of blooms. Plants will grow from 1 to 5 feet.
An old-time gardener's favorite, nasturtium is extremely easy to start from seed and will reward gardeners with an abundance of colorful blooms and interesting foliage. Once nasturtiums begin to grow, they require very little care and both leaves and flowers are edible and make excellent garnishes for culinary delights.
Coleus is a stinking foliage plant that can be red, green pin white, purple or yellow. Small flowers will appear in late summer and can be pinched off to encourage bushier foliage. This plant makes a lovely addition to a mixed container garden or does equally well when planted in a shady garden spot.
Popular Trees and Shrubs
Trees and shrubs are a lovely addition to the landscape. Use them as a focal plant or together for a hedge, living fence or windbreak.
Barberry is a cold hardy shrub with beautiful deep burgundy foliage and very sharp thorns. Plant in full sun for best results and prune to your desired shape.
Juniper is a beautiful feathery evergreen shrub that is perfect for rock gardens, trailing over walls or for filling in garden spaces quickly.
This medium size conifer has bluish-green needles and grows to a mature height of 75 feet.
Although cold season vegetables do best in this region, all of the common vegetables grown elsewhere in the United States can be grown with a little extra care. It is best to plant vegetables in raised beds and start plants such as tomatoes, peppers, celery, cucumbers and zucchini inside or purchase transplants. Purchase short season varieties and use black plastic to warm beds prior to planting.
Even though the growing season is short in the interior of Alaska, gardeners can have a lovely and colorful garden if they choose plants appropriate for this region. Use the general USDA zone 4 map to get an idea for your basic plants and then follow with the more specific information provided by Sunset for best results.