[permaculture] "Repairing" winter kill apple & pear trees
dwoodard at becon.org
Tue Jul 13 02:53:57 EDT 2010
Sherman, what is your usual lowest winter temperature, and what is the
As well as early cold in the fall, one thing that is very dangerous is a
winter thaw followed by very cold temperatures, such as the classic
Alberta prairie "chinook" followed by a cold snap. The coldest part of
winter typically January-early February, being followed by a thaw brings
the tree out of dormancy and it will never fully recover its earlier
coldhardiness even if subsequent cooling is gradual, but it often is
not. Then an abrupt cold spell can really hammer a tree.
At Vineland Station here in the Niagara Peninsula where the historic low
is minus 16 degrees F. they were unable to keep Sansin Manchurian
apricot alive because of its tendency to come out of dormancy very
easily, although it is coldhardy in southern Manitoba close at around
minus 40 F.
You don't mention cultivars. There is enormous difference in
coldhardiness among cultivars in a given species. I used to know a
grower who lost half his Cox's Orange Pippin apple trees in Agriculture
Canada zone 6a at Milford in the southeast of Prince Edward County, the
peninsula that juts into Lake Ontario from its north shore, in the test
winter of 1980-81. Yet the hardiest apples survive in zone 1b hundreds
of miles north of Edmonton, Alberta. Apples are grown at Fairbanks, Alaska.
Some nurseries that may be useful are:
At the latter, check out Redstone Canyon Gold apple which originated in
Colorado (though I don't know the altitude at which it was selected).
Also, their Carlos Queen apple was selected near
Rocky Mountain House in the Alberta foothills, Agriculture Canada zone
2b, quality reputed not the very best but good, picks September, keeps a
few months, fresh eating and cooking, decent size.
If your conditions are really tough, check out
Alaska Pioneer Fruit Growers
Anchorage is a lot milder than Fairbanks but both have unusual day
length and summer temperatures and not all otherwise coldhardy apples
Evans/Bali from St. Lawrence Nurseries may be the hardiest readily
available sour cherry on a larger tree. The University of Saskatchewan
dwarf sour cherries are likely hardier; see links from
There is some interesting information on this nursery website:
Luscious pear was bred at Brookings, South Dakota. From what I've read,
it's hardy to Ag Can zone 4a, has fruit a little smaller than Bartlett,
flavour similar but more intense.
Patten is an older hardy pear of good repute for canning, for at least
some parts of zone 4.
The Agriculture Canada station at Morden in southern Manitoba, zone 3b,
bred hardy apricots from crosses between Prunus armeniaca and Prunus
mandschurica (often considered a subspecies) resulting in Morden 604 and
Westcot, the latter reported more regular in bearing. There are some
pure Manchurian apricots around such as Brookcot and Prairie Dawn which
may be a little hardier to deep winter cold but more vulnerable to
dormancy problems due to thaws.
Krikon Damson plum from Sweden (for preserves) if you can find it is
considered hardy at Morden.
Mount Royal European plum is well liked in northern areas for fresh
eating and preserves, and is marginally hardy at Morden.
Some selections of the hardy kiwi species Actinidia kolomikta have been
hardy at Morden; it is said not to like full sun. It's high in Vitamin
C, to 300 mg/100 gm.
Another organization which may be useful to you although not specially
oriented to cold winter areas is
St. Catharines, Ontario, Canada
Stephen Sherman wrote:
> Thanks for the advise, and here are some more details...
> I am in Colorado in the mountains at ~8300' elevation. Orchard is on a
> slope with ESE exposure. Soil is a sandy loam. Rather low in P, good to
> a bit high in K and low in N (also some trace deficiencies in B, Mn and
> S according to soil tests). We tend to have dry climate (~20" precip per
> year) and I irrigate as needed, including in winter when the soil is not
> frozen. It can be quite windy here (winds up to 80-90mph are a common
> I have been on a program to improve the soil in the orchard. Fall
> application of composed manure (can't use in spring/summer as it
> releases N way too late in the growing season here). I also have been
> using some conventional fertilizers mostly for building P, but they come
> with N most often (MAP and DAP). I'd love to use soft rock phosphate,
> but using that for large areas is cost prohibitive, unfortunately. I
> don't think the N application last spring (all before bud break) was
> excessive, at least for a normal fall; just that it contributed to late
> growth and a lack of hardening off in combination with the weather and
> deer damage. However I am cutting back on the soil program for a variety
> of reasons, the apple trees among them.
> The trees which died outright were primarily cherries, peach and pear.
> All of those are marginal here and perhaps last winter was a wake-up
> call for me to not waste time on trees that will die within a few years
> even if they do well at first. Most of the apple tree damage looks like
> winter kill. On some there is the obvious bark discoloration and bark
> splitting. No doubt due to lack of hardening off in time for the cold
> snap, and our bright sunny and cold winter days. I use spiral trunk
> protectors and tree wrap, and for the most part the areas covered by
> those made it through OK; although there was some splitting under the
> protectors on two trees. I am considering painting the trunks and lower
> branches with diluted latex paint for this coming winter as that should
> Some of the trees did not show any bark discoloration or splitting, but
> the bark on the upper part of the tree just dried up. That is got
> wrinkled and dry looking. A cut and lift of a small bit early in spring
> showed no green cambium in these cases. This may be due to dehydration
> over the winter. It was especially cold and windy last winter, but there
> was lots of moisture (in the form of snow), so much that I could not do
> my usual winter irrigation as the ground was snow covered and frozen
> from Dec til April. Perhaps due in part to the lack of proper hardening
> off in the fall? Again all of these trees had made it through several
> previous winters here without issues.
> I was thinking that foliar feeding with a P and K base plus kelp might
> help. At least for the trees which are not exhibiting good growth from
> the parts which are growing. But I was a bit concerned that putting on
> an imbalanced fert might cause more issues.
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