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  • From: Bernie Nikolai <Nikolai@v-wave.com>
  • To: nafex@egroups.com
  • Subject: [nafex] Apple Dwarf Rootstock Hardiness in Zone 3
  • Date: Tue, 3 Oct 2000 20:24:43 -0600 (MDT)

It may surprise many Nafexers how hardy dwarf apple rootstocks are IF they
have a snowcover of at least 4 to 6 inches. Here in Edmonton, I am aware of
several trees on rootstocks that most would think would not survive here.
As an example a friend has a 15 year old tree on M27, and a few trees on M9
have survived fully for several years.

The key is mimimun soil temperatures under the snow. According to tests
here in central Alberta, even in mid January at -40C or colder air
temperature, soil temperatures under the snow rarely get as cold as -10C,
and this is uncommon. Usually minimum soil temperatures in a winter (under
the snow) here bottom out at -6 to -8C. From what I've read, even tender
apple rootstocks such as M27 and M9 can take -8C before damage and death
begin to occur. The key is a permanent, non-melting winter snowcover, which
we get in abundance. I'm sure more mild areas with poor or non-consistant
snowcover will have more trouble wintering over apple rootstocks in the
field than I would. Without snow, the soil temperatures can easily drop
below -10C in a cold snap. Also freezing and thawing of the soil is VERY
hard on apple rootstocks after the 3rd or 4th freeze/thaw cycle. Here in
central Alberta once the ground freezes, its frozen solid until April.

Here are some of my comments on dwarf apple rootstocks that have survived
well in central Canada, zone 3/2.

M26 - A friend has about 24 trees on M26 that have survived 100% over the
last 18 years west of Edmonton. The key with this rootstock, while hardy,
is that it is VERY drought intolerant. My friend has drip irrigation. In
other trials on the prairies, Morden Experimental Station as an example, M26
has failed and was deemed not hardy. However these tests were conducted in
unirrigated conditions. My guess is the rootstock died of drought stress,
not cold.

Ottawa 3 - Three weeks ago I visited a commercial apple orchard near
Saskatoon, Saskatchewan of 4000 trees, all on Ottawa 3. The trees are up to
7 years old, and apparently not a tree has died due to the rootstock
failing. But here again, central Saskatchewan, like central Alberta, gets a
consistant snowcover all winter. This rootstock, while hardy and drought
resistant, HATES to be moved as the roots regrow slowly. The commercial
orchard I visited plants 6 inch tall Ottawa 3 rootstocks in place, and
grafts/buds onto the trees in their permanent location in the orchard when
they are large enough. I've found moving trees on Ottawa 3 rootstock seems
to "shock" them. They go into a sort of "suspended hybernation" for 2 or so
years with very little if any growth to the tree until the roots regrow.
Then they grow normally again, but you've "lost" a couple of years.

Bud 9 - I have several trees on test on this rootstock, zero problems so
far, but its only been about 4 years.

Bud 490 - This seems to have a lot of potential in zone 3, yet very few if
any people seem to use it. This rootstock is free standing, hardy, semi
dwarf, fireblight and drought resistant, and very productive. I understand
from tests in New Brunswick this rootstock does poorly in climates with soil
freeze/thaw cycles during the winter. But if your soil freezes consistantly
and doesn't thaw until spring, this is an excellent rootstock!

P22 - While fully hardy for me after 4 years, I wouldn't recommend this
rootstock due to extreme fireblight sensitivity.

Vineland Series, V1, V2, V3 (from Vineland Research Station in Ontario)-
These rootstocks are in the dwarf to semi-dwarf catagory, and are apparently
very hardy (Kerr applecrab is one parent) and fireblight immune/resistant.
Mine have survived 2 central Alberta winters with no problems, but a lot
more hardiness testing needs to be done.

The bottom line is despite what we may have been told, certain dwarf apple
rootstocks do indeed grow and produce well in cold zone 3 and even zone 2
conditions. However consistant snowcover, and with some dwarf rootstocks,
irrigation is required. It is also important NOT to have grass competition
around the trucks of the trees for best results. Clear cultivation does by
far the best, from my experiences anyway.

Bernie Nikolai
Edmonton, Alberta


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  • [nafex] Apple Dwarf Rootstock Hardiness in Zone 3, Bernie Nikolai, 10/03/2000

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