[NAFEX] Cold Peaches ?

Dave Griffin griffingardens at earthlink.net
Thu Dec 1 14:38:38 EST 2005

Hi Richard and all you other Northern growers with a bad case of peach envy,

  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 years. 
  Here are some things I have learned, many the hard way, about growing peaches in a cold climate:
   1. 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.
   2. 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. 
   3. 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. 
 4. 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?
 5. 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?). 
 6. 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! 
 6. 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.
 8. 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. 
 9. 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.
 10. 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.
  11. 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.



----- Original Message ----- 
From: Richard MURPHY 
To: nafex
Sent: 11/21/05 7:03:01 PM 
Subject: [NAFEX] Cold Peaches ?

Hi Gang;

Today's question is about peach trees.

I see 3 varieties listed as 'hardy'.

Reliance   -   Intrepid   -   Contender

All say 'zone 4'.
Descriptions vary, some claim bud & flower hardiness, too.
That's where my big orchard is; zone 4 central Maine.
Do any of you have first hand experience with peaches in southern zone 4 or colder?
I intend to trial 2 trees of each, starting in spring '06.
Anyone been there ??


Richard Murphy

PS    Remember that all that stuff you may consider to be common knowledge, perhaps laying idle in your brain for years, can be dug up and tossed at a novice such as myself. It is received, used, then tucked away for the next dreamer.
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