Found this over on NAFEX. Must pass it on to some people here with questions. I found this information to be excellent. Plan on using it in the future. Its long, but a very good read...print it and keep a copy. This should be a sticky or in a FAQ.
Welcome to the asylum.
I've been finishing up the hurry-up, freeze-up! work and haven't been able
to get to this until now.
I have been experimenting with growing peaches and other tender fruit
trees in zone 4a, central MN, pretty intensely since 2000 and less so before
that. I am a collector, tester, grower and breeder and have an experimental,
mostly one of a kind, collection of over 350 trees. Many of these are hardy
here (I think I may now have the largest collection of hardy plums in the
US) but some are tender and would not survive without some modification to
standard "plant and wait" horticultural practices. I have apricots, sweet
cherries and European plums that fit this description but the largest number
of these tender trees and the most tender of them are the peaches. Still, I
have been able to test around 85 named cultivars and have around 55
survivors currently, both named and private selections. They are growing as
branches on 45 hardy peach seedlings that are offspring of the Bear Creek
Siberian C based material, which are also the basis for my testing and
breeding. (Some of you have contributed material for testing or have
provided information that has helped me to track down promising material and
I am grateful.) I know that growing the test branches is not a true measure
of absolute hardiness but it gives me an indication of relative hardiness.
If a cultivar survives as a branch then I make up trees to plant out for a
second test, if not, I am through with it.
Meanwhile, the branches provide me with breeding material which I use to
make crosses on the better selections of the seedlings. Breeding trees have
been selected based on fruit size and quality and on early ripening, which
is important for hardiness as early ripe trees have more time to harden off.
These are the seed parents for crosses made using pollen from the good
quality named cultivars with a known track record for hardiness and/or those
having a long chill hour requirement, which is linked to hardiness. For
pollen parents, I have chosen from the older cultivars of commercial and
backyard/farmers market types rather than from newer commercial ones. This
is because hardiness and other desirable characteristics seem to have become
secondary considerations in contemporary breeding programs to firm flesh and
other commercial qualities. My goal is to produce a peach that I can grow
and eat in MN rather than one that looks good on the shelf in a grocery
store half way across the country. I also use pollen from the private
seedling selections I have collected and, of course, I am making reciprocal
crosses on the good quality branches when their flower buds survive the
winter. The first planting from the crosses of selected seedlings x Harrow
Diamond made in 2004 were grown out this year. They made around 3' of growth
and should provide a small amount of first fruit for evaluation in two more
Here are some things I have learned, many the hard way, about growing
peaches in a cold climate:
- Hardiness is much more complex than minimum winter temps. Especially
so are the conditions in the fall when trees are going dormant, which is
almost never given the attention it deserves and may be at least as
important as winter minimums. Many trees thought to have been killed during
a late Jan/early Feb deep cold spell may have already been dead from a
sudden change to cold in Dec/ Nov, even though the temps were less severe.
Of course when they don't leaf out in Spring the mid winter cold is blamed.
Last years minimum was only -23 F with good snow in late Jan, which should
have been easy for my trees, but we had sudden unusually cold temps for a
long period in December before there was snow cover and so there was a lot
of damage and mortality in the peaches.
- The weak link in peach tree hardiness is the trunk. A tree goes
dormant from the top down and the last thing to harden off is the trunk. An
early cold snap that comes in before the trunk hardens off can kill the tree
trunk without damaging any other part of it. I have learned to delay
celebrating tree survival in spring beyond an examination finding green twig
cambium right out to the tip of every branch and plenty of live buds. Too
many times I have seen those buds break into lush growth only to then stop
growing abruptly and then dry up. This is because, as it has turned out too
many times, the trunk was dead just above the soil line. I am experimenting
with budding and grafting 2'-3' high on the rootstock in hopes of providing
a hardy trunk.
- Bailey rootstock is not the answer to hardiness problems. It may well
be a vigorous rootstock that is itself hardier than most peaches, but it
grows too long into the fall and induces the scions grafted on it to do so
as well, delaying senescence. The common peach seedling rootstocks Lovell,
Halford and Nemaguard also have this effect, as does Pumiselect and the
plums St. Julian 'A' and Mariana 2624. Siberian C based peaches defoliate
early and induce the scion grafted on them to do so when used as a
rootstock, or at least it doesn't get in the way. Some other plum
rootstocks including P.americana and, less so, P. bessei so the same. I am
experimenting with various cherry plums as rootstocks for peach with this in
mind. Scion overgrowth? Sure, but the tree will probably be dead from other
causes before this becomes a serious problem and staking is easy. Suckering?
Its easy to cut off the suckers. An additional benefit of using plums is
that you can then grow peaches in heavier soil than you otherwise could.
- Warm wet weather in fall trumps rootstock in the battle to get the tree
to shut down. Tarping off the roots seems to help but sweating and the
continual presence of the tarp does not permit drying out of the soil
between rains. I wish I knew how to do this without having to roll the tarp
up in good weather. Anybody?
- Southwest injury is a big problem. For those who are blissfully
ignorant of SW injury, here is the story: its a cold day in January with
high pressure in control. There is only a light breeze and a few white puffy
clouds in the the clear blue sky. At 2:00 PM the high temp for the day of
minus 15 F is approaching but while the low sun angle doesn't provide much
heat to the earth (thats why its winter) it feels warm on your face despite
the cold. It is also warm on the vertical tree trunks and their temperature
has risen to way above 0 F. Then the sun dips behind one of those clouds for
just a few minutes but that is long enough to make you feel cold and to
bring the trunk temp suddenly goes back to -15 F. Sun, shade, hot, cold...
repeat until cambium is completely dead on the southwest side of the tree.
Even if the tree isn't killed outright the tree is doomed because there is
now an entry point for insects, bacterial canker, you name it. Pertinent
contributing factors: when the weather is the coldest the sun angle is near
its lowest, and, the farther North you are the lower the winter sun angle
and the bigger the danger of SW injury. By all means paint the trunks white
as high as you can reach and put on white tree wrap/guards (why do they even
make brown tree wrap?).
- Don't plant a tender tree in a "protected" site. I wish I knew how many
times someone has told me about the peach that died in spite of their having
planted it in this great warm and wind protected site right up along the
south side of the house. Absolute cold kills peaches not wind chill unless
you are in a prairie climate with dry snowless winters, and then that is bud
desiccation, not wind chill. And minimum temperatures come around sunrise,
way after any benefit from yesterday afternoons buildup of slightly warmer
temperatures in the tree's little heat island is long gone. Once in a while
I even hear about someone who has tried to espalier a peach against the
south wall of a building in an effort to get it through the winter - Geez!
- Plant your peach on the north side of a shade source - building, row of
evergreens, etc. It should be located far enough away so that it gets full
sun in the summer but close enough so it is in the shade through the coldest
winter months and up to bloomtime. Tender trees can survive severe cold,
often colder than they are rated for, if they remain in deep dormancy. I
found that many zone 5 trees were hardy in my zone 4a temperatures when they
survived -29 F during the winter of '03-'04. Often the zone 5 rating
reflects a trees inability to resist de-hardening in a warm spell and/or to
recover from it and re-harden when the weather turns cold again... rather
than its susceptibility to cold midwinter temperatures. Winter shade helps
keep the tree dormant during winter warm spells, delays its breaking
dormancy in the spring, and delays bloom. In addition, no winter sun on the
trunk = no SW injury.
- Peaches and apricots are a good risk in cold climates. They are very
vigorous and so recover quickly from winter injury. Since they bear fruit on
one year old wood they are always just one good winter away from a crop. So
for an established peach that has died back to the snowline in winter, it
would not be unreasonable to see 6' of new growth during the next summer
which would then bear fruit the following summer after a mild winter.
Madison and Hardired are good choices in spite of tender flower buds because
they are very wood hardy and the tree is more likely to survive a cold
winter in good condition even though the flower buds may die, then they can
produce a full crop the next year if a mild winter follows. By contrast, my
sweet cherries need two mild winters to get fruit - one to form spurs and
another to get fruit. Every cold climate gets occasional mild winters but 2
in a row is rare.
- Don't plant a peach tree thinking that at some time in the distant
future, grandchildren at your side, you will be able to look back and fondly
recall this day. Plant peaches like you do tomatoes expecting their demise
and planning for their replacement. Even in ideal climates and conditions
peaches are not an icon for longevity and for sure they are not going to be
when you plant them on the fringes of their range and beyond. Better to
take heart in the fact that they are vigorous and precocious (I've had a
partial crop on peaches in their second growing season from the graft ) and
you might get lucky for a while with a few unpredictable crops before the
tree dies... and that they are so very good that when you do get them it is
worth the risk and work.
- Reliance is not the hardiest cultivar, and it doesn't have to be. There
is a group of relatively hardy varieties, named and unnamed, that includes
Reliance but also Veteran, McKay (at least as hardy for me as Reliance in
flower and wood) and Madison and Hardired Nectarine (might be a little more
wood hardy). Within this group, planting site and horticultural methods are
much more important than which cultivar you choose to grow. The "Haven"
peaches from MI have done well for me as have the "Prairie" series from IL
and the Harrow varieties. 'Sunapee', the other peach besides Reliance out of
NH, has done well as have WI Balmer, Champion, and Polly. But again, let me
emphasize, its not which cultivar you choose within this group but how you
grow it. Somewhere warmer than here the choice of cultivar may be enough to
make the difference but in my location this alone is not enough as my pile
of dead trees will attest. From what I have learned by listening to the
problems people have growing peaches in zone 5 and even warmer, any place
that has serious winter to the extent that they hope to have a white
Christmas - whether they get one or not - could benefit from some or all of
these growing principles.
- For those of you planting seeds and making your own grafts, no one
year old peach tree is hardy regardless of cultivar. You could get lucky
with heavy snow cover or a mild winter but to ensure survival for the first
winter you have to dig it up a tree and heal it in at an angle with mulch
over the top, or protect it some other way. Any hardiness a peach may
eventually have comes about with age and is not present the first year. I
don't mind killing trees if I learn something from it but nothing is learned
from losing a one year old tree.
Good Luck and remember that grow is a verb.
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