Growing tips for the far north

A prize-winning garden in the Arctic or Subarctic need not be difficult if you understand how the climate affects the success of your garden and what techniques can be used to compensate for far north growing conditions.

A basic knowledge of gardening in the far north is essential to manipulating the conditions that affect your garden’s success. For example, it is very important to plant your garden as soon as the danger of frost is past, as each day lost is comparable to losing 1 ½ to 2 days in a temperate climate. The most significant factors affecting a Northern garden are the length of the day and the temperature of the soil.

First let’s discover how day length affects plants. Long days affect varieties not suited for the far north by causing bolting- prematurely going to seed- often leaving the gardener without an edible harvest. Bolting is easily overcome by selecting varieties which perform well under long days. All varieties sold by Denali Seed have been tested and perform well under Alaska’s long summer days. However, even the best varieties of spinach are a problem and must be planted very early in the spring and again in late summer to avoid the summer’s longest days and reduce bolting.

The second factor, low soil temperature, requires a little more effort to overcome. In Alaska the soil temperature is in the mid 30s at planting time. There are two main factors to deal with. The first is to reduce cooling from evaporation, and the second is to use solar energy to raise the soil temperature. The first may be accomplished through the use of a clear plastic wind barrier on a fence which allows light to pass through but reduces air flow across the soil and the subsequent cooling from surface evaporation. When gardening in areas where heavy winds prevail, a windbreak will reduce plant damage, hasten maturity and increase production. When the plant leaves are whipped and damaged by the wind the plant cannot produce adequate food to mature the crop. The wind’s passage over the soil surface evaporates the surface moisture, which creates a cooling effect, reducing the soil temperature, which in turn delays or reduces production. A hedge or other natural windbreak can be used, but a nonliving windbreak will not compete with the garden plants for moisture and nutrition. If a clear plastic barrier is used, the sun will penetrate and shine on the plants close to the garden’s edge. An ideal windbreak is three-sided with the protected sides facing the prevailing wind and the open side, if possible, facing the lowest terrain. This allows the cold night air of early fall to drain away from the garden, delaying or avoiding the frost which occurs in the lowest terrain.

The second approach, using solar energy, can take any of several forms. Mounding of the soil so that the slopes are at a 45 degree angle facing the sun will warm the mound, but be sure the top of the mound is at least 8-12 inches across to prevent rapid drying of the soil.

The most recent and most effective innovation to raise soil temperatures is the use of a clear plastic mulch. The advantages of a clear plastic mulch are better germination, accelerated plant growth, faster maturity, and reduced moisture loss. The clear plastic mulch fosters faster and more complete gemination because of the increased soil temperature. The soil under the plastic loses very little water through evaporation and the soil warmth is not dissipated through evaporation by the wind. On sunny days, air temperatures have been found to be 30 degrees warmer than the surrounding air under the plastic mulch. This warm air transfers some of its heat to the soil beneath.

When using the clear plastic mulch, prepare the soil, fertilize, and plant the seed as you normally would. Then spread a 3 or 4 foot wide sheet of 1.5 to 2 mil plastic, centering it on the row. Fold both edges back 6 inches and dig a 4 to 5 inch trench on both sides. Now lay the edges of the plastic in the trenches and cover them with soil. Be sure to keep the plastic taut when filling the trenches. When this has been completed, secure the two ends the same way. If the plastic is not fastened securely, it will be damaged by the wind.

As soon as the seedlings break through the soil’s surface, openings must be cut in the clear plastic mulch to release them. If green beans and other broad-leaved plants are not released immediately, they will sunburn. This will either stunt or kill the young seedlings. Sunburn is a result of the high temperatures under the plastic. Sweet corn, however, grows well in the high temperatures under the plastic and does not have to be released until the plants are 3 to 4 inches tall and the danger of frost is past.

Plants grown through plastic have to be supplied with additional water, which is done through the openings from which the plants are growing.

Weeds will grow under the clear plastic but do not seem to hinder the garden crop if adequate water is supplied. The weeds may be pulled by loosening the plastic on one side, then replacing it after weeding. The use of herbicides is not recommended for most home gardens.

Raised beds are also a good way to increase the soil temperature. The raised bed should be at least one foot high to allow the warmer surrounding air to heat the soil and at least 2 feet wide to help prevent the soil bed from drying out. Wider beds may be more convenient but will not warm the soil as effectively. Raised beds are the most common and easiest method of raising soil temperature, but is also the least effective of the methods described.

The above methods, used alone or in combination, will raise the soil temperature which will decrease the time to maturity on plants with cold-sensitive roots such as sweet corn, green beans, cucumbers, tomatoes, and squash. Less sensitive plants will also benefit from these techniques.

Gardening in the subarctic is not difficult for the prepared, and these tips will help make your garden more successful and your rewards more plentiful.