By Bob Purvis
Getting a 1- or 2-year-old fruit tree to survive an Alaskan winter is not all easy task even if the tree is a hardy Canadian apple variety on an Antonovka or Ranetka rootstock. With winter almost here, it may be worth outlining practices that improve the odds of tree survival. These were developed during my nine (9) years of growing apples in Alaska and watching the successes and failures of others.
Possibly the hardest thing is to induce the young tree to go dormant in a timely fashion. Applying slow-acting sources of nitrogen in August or September (e.g., steer manure) is a grave mistake. As a rule, and especially in the first year, no fertilizer should be applied after mid-July. In view of the sharp increase in rainfall from July to August to September, I advise not watering the tree after August 1 unless there is a period of sunny, dry, warm weather and it appears obvious that the soil is drying out.
Sunscald is a bark injury resulting from direct sun shining on and thawing the sap in the lower part of the tree trunk in late winter and early spring, if the thawing is followed by rapid freezing. The subsequent rupture of capillaries in the cambium (living tissue layer) under the bark can result in the bark coming loose and later tree death. Protection from sunscald is very important for young apple, crabapple, pear, and mountain ash trees because of their thin bark. White plastic tree guards applied in early October and removed in early May are the best source of protection from both sunscald and rodent damage. Unlike burlap or paper, they do not maintain a continually wet surface in contact with the tree bark during wintertime thaws and break-up, which may promote rotting of the bark.
Protection of the roots is best done by mulching the soil out 1-2’ from the base of the trees after the soil freezes and after applying the tree guards, I say “after” because the materials which are best suited for mulch, dry leaves held down by a layer of grass clippings or spruce boughs, can otherwise provide a great home for mice during the winter months The layer of mulch should be at least 4” thick. Its purpose is not to keep the ground from freezing, but rather to prevent the ground from alternate freezing and thawing during the winter months. The mulch should be removed as soon as the snow melts so that the sun can warm the ground.
During the winter of 1991-92, Anchorage experienced unusually heavy snows, resulting in breakage of a number of branches on bearing fruit trees. To cope with this situation, I strongly advocate training the tree to a central leader and staking the leader. When the tree initiates branches in the spring, encourage them to form at least a 40-45° crotch angle by inserting toothpicks or clothespins in the crotch while the wood is still limber; these are structurally sounder under heavy snow or fruit loads than narrow crotches. In mid-October (October 10-20), if your trees have not dropped their leaves, it’s a good idea to strip them off by hand (the leaf blades are what catch the snow; the petioles [stems] of the leaves can be left). Lastly, shake the snow off your trees as it falls if the snowfall is wet heavy, and deep. It takes only minutes to do this, but it takes months or years to grow a replacement branch!
Provision of protection from moose-browse damage is something which should be done at the time the trees are planted. My personal experience was that for a few trees, building enclosures or cages of 2´2 s and chicken wire around the trees worked quite well. For a larger planting, I found that a 7½ high welded-wire fence, supported on metal T-posts, worked quite well in keeping the moose out. If rabbits are a problem, such a fence should be extended down to ground level.
One last precaution which would probably help with bud survival on cherries and other stone fruits is to spray the tree branches with an anti-desiccant such as Wilt-Pruf or Yapor-Gard so that winter winds do not dry out the tree and buds when the tree is unable to take up water.
In the fall of 1988, I was faced with overwintering a large number of fruit trees in pots. I built an enclosure about 5’ high, but open to the sky on the back of my greenhouse; put all the trees in their pots inside it; and after the ground froze, I applied tree guards and a heavy layer first of dry leaves, then of grass clippings to hold them down. Under these conditions, hardly any trees died or suffered severe winter injury after exposure to -34°F. The trees in pots included not only apples, but also a Ure, a Hudar, a Nova, and a Tyson pear, plus 2- year-old trees of Toka and LaCresceot plum. All of these survived, howbeit there was some winter injury on the pears.
In summary, preparing fruit trees for winter involves proper management of fertilizer and water; proper training and support of the tree branches and trunk; removal of leaves; and protection of the bark from sunscald, the roots from alternate freezing and thawing, and the entire tree from moose and rodents. This may sound like a lot of work, but remember that with each winter your tree survives, the odds of further survival are increased, and the fruit it ultimately bears will be more tasty and fresh than most you can buy in the supermarket.
And speaking of moose, Betty Cloud, of Kenai, offers the following…
I have a tip for moose repellant. It has worked very well or me. Last year, I had three (3) cows and five (5) babies in my yard off and on and all at one time. Every bush, tree, or plant I had treated was left intact-no samples taken!
Blend two (2) eggs with water in a blender. Put this mixture into a gallon milk jug and fill with water, 3-4 days later it is ready to put in a spray-type container for spraying your lilacs or anything else! The first year I did this, I did it often, especially after hard rain. Now, I don’t have to do it as often. The moose seem to pass up things they have found unpleasant in the past Be sure you check wind direction before you spray. Once it dries, people don’t know is there.
I am 30 miles out of Kenai, out past Nikiski-these animals are not wandering the streets of Kenai. I have not tried this on cabbage, etc, I use reemay cloth and it helps a great deal.
I also continue the Fairbanks trick of planting my carrots in October, just before freeze-up, under reemay cloth. It works great. They sprout faster than spring-planted seeds.
I enjoy all the tips and information on plant trails. We have lived in Alaska for 40 years and wasted a great deal of money trying different trees and berry bushes. This association helps cut the time we waste on things doomed to freeze-out. Hope you had a great summer!