GBG Note 27

GBG Note No. 27

Horticulture in Alaska's Great Interior

By Dr. Patricia S. Holloway

Plant a few flowers in Juneau, Alaska and expect to try a litany of diversionary tactics to redirect the massive amounts of water cascading from the sky and flow down the hillsides. Prepare to battle an army of slugs that march relentlessly through the vegetable and flower gardens. Endure high electric bills as you plug in and light up to chase away the gloom of overcast, dripping skies. Move to Anchorage, and the picture gets a little brighter and the slugs not as menacing. However, be prepared to clean up after storms that leave plants coated with ice, and to endure wide fluctuations in winter temperatures, occasional damaging high winds, and cool, cloudy, overcast, often wet summers.

Move even further north to Alaska's Great Interior, and join the ranks of the truly great, horticulturally challenged gardeners! Summer temperatures climbing into the 90s; winter temperatures dipping to a teeth-rattling -60oF and colder; snowfall ranging from a few inches to more than 12 feet; cold soils; desert-like amounts of rainfall; a very short growing season; nearly twenty-four hours of daylight in mid June; and only about four hours of light in mid December – – all of these factors combine to challenge even the most experienced gardener.

In Interior, Alaska, only the hardiest plants in the world can withstand the long, cold winters and extremely short summers. Once snow begins to fall, it rarely melts until spring, and the temperatures dip steadily as the daylength slips away. Few commercial greenhouses operate throughout the winter because of very high electricity and fuel costs. Gardeners move indoors with windowsill gardens, light tables and small greenhouses. Seed catalogs begin arriving in November, and long winter hours are spent planning and plotting the next season's garden. Outdoors, trees and shrubs are subjected to punishing temperatures and extremely low humidity. Snow becomes powdery dry, and the neighborhood moose snaps the tops off those prized paper birch saplings in the front yard. Hares girdle the trunks and nibble the needles off the lodgepole pine trees, while voles tunnel beneath the snow, munching on lily bulbs.

With temperatures hovering in the subzero zone, the gardening season officially begins in late February or early March. Nearly every plant grown in the vegetable and flower garden is started from seed in the greenhouse or under lights. Seedlings of geraniums and begonias are started first, while some of the squashes and broccoli seedlings spend only four to six weeks indoors. During the last week of May, plants are moved outdoors to cold frames, and they are gradually exposed to stronger sunlight and cooler outdoor temperatures. Memorial Day marks the traditional beginning of the planting season when perennial ornamentals, roses, wildflowers, fertilizer, compost and thousands of flower and vegetable bedding plants migrate from local greenhouses to backyard gardens. Homeowners and commercial businesses across the state help make the greenhouse industry the largest agricultural industry in Alaska by a massive distribution of plants that takes place within a few short weeks in May and June.

Many gardeners will try their luck at growing Alaska's famous giant vegetables. Not all vegetable varieties grow to be giants under the midnight sun. Long daylengths, cool summer temperatures, good growing conditions, and the plant's genetic makeup combine to produce the giant size. The famous giant cabbage is the variety, 'O-S Cross' or 'Flat Top'. The record cabbage grown in the Tanana Valley was entered in the 1988 Tanana Valley State Fair by Victor La Jiness. It weighed 63.5 pounds (28.5 kilograms)! Because of hotter and shorter growing season, Interior gardeners don't match the state record of 99 pounds for a cabbage grown in the Matanuska Valley just north of Anchorage.

Another Giant is 'Shogun' broccoli, a late-maturing variety that produces dinnerplate-sized heads (14-inch; 35 centimeters diameter) and weighs up to 4 pounds (1.8 kilograms). Other vegetables become large because they are left in the garden until they are over-mature. Zucchinis larger than baseball bats and soccer ball-sized turnips, rutabagas and kohlrabi are often grown as novelties for the Tanana Valley State Fair held annually in Fairbanks.

Most gardeners are satisfied with normal-sized vegetables and flowers, but the very long daylengths (21 hours and 52 minutes on June 21) make some varieties a real challenge to grow. Most spinach varieties and many beets grow so fast they bolt and bloom without producing edible leaves and roots. Chinese cabbage, many types of mustard greens, and some carrots and radishes produce seed stalks so rapidly they are good only for the compost pile. Onions grown from seed do not form large, storage-type bulbs. Certain varieties of winter squash and fall-blooming chrysanthemums do not bloom because the daylength is too long.

Despite these tales of woe, gardens grow very well in the great Interior. Sweet-tasting potatoes are harvested by the ton. Broccoli, cabbage and cauliflower are second to none in the world for size and quality, that is if the moose don't eat them first! Pesticides use is infrequent or nonexistent because many pests that plaque "lower 48" gardens do not survive the harsh winters. By the end of the summer local stores and farmer's markets are bursting with hothouse tomatoes and cucumbers, fresh herbs, lettuce and other types of greens, peas, beans, turnips, rutabagas, kohlrabi, carrots, beets, and a dazzling array of intensely-colored flowers. The long daylengths and warm summer temperatures promote rapid growth and maturity within a very short period of time. Even artichokes, sweet corn, pumpkins, cucumbers, tomatoes and peppers hot enough to cry for will mature with the aid of soil-warming clear plastic mulches. By summer's end, gardeners are exhausted from the seasonally-intense gardening frenzy. Most welcome the long cold days of winter to build up reserves for another season to come. An when the first catalog comes in the mail, it starts all over again!

School of Natural Resources and Agricultural Sciences

University of Alaska Fairbanks, PO Box 757200, Fairbanks, AK 99775