Handling cold-hardiness

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matt lustig
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Joined: Sat Jan 28, 2017 10:05 pm

Handling cold-hardiness

Post: # 71759Post matt lustig
Wed Jul 01, 2020 12:12 pm

Although USDA hardiness zones are based upon mean minimum temperature, I have generally thought of "actual hardiness" as being due to a lot of factors other than just temperature. For instance, I've thought of actual hardiness as being very influenced by wind exposure (which dries out buds, presumably) and temperature fluctuations (i.e. warm late-Winter temperatures leading to bud break right before a cold snap). I've also generally thought of the roots as more susceptible than stems to the stresses of cold weather. So for instance, I've occasionally taken a small number of potted roses that I've been worried about, dug the pots in, bent over the stems, and covered the stems with sand. Although six inches of sand probably had almost no influence on the actual minimum temperature that the plant was exposed to, it would of course have a huge impact upon the plants' exposure to winter winds and temperature fluctuations.

Do any of you have experience with whether the hardiness of tender roses is primarily based upon simple minimum temperature, or more based upon these other factors? My motivation for inquiring is that I am considering incorporating one or more tea roses into my stock, to breed with diploid roses that are hardy at my location (Zone 6b). My uninformed theory is that such a rose would probably do fine with proper protection--not protection from the actual minimum temperature, but protection from these other factors. Any thoughts? To clarify, I am NOT talking about bringing such a rose inside, but merely protecting from the non-temperature factors.

Matt Lustig

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Re: Handling cold-hardiness

Post: # 71760Post rikuhelin1
Wed Jul 01, 2020 2:54 pm

Live in equivalent of USDA zone2-3, CDN 3-4a. In the early years planted scores of teas, hybrid musks, HP, Damasks, bourbons, portlands, HTs, gallicas centifolia austins. etc etc. Protected by covering with 42 bales of compressed peat moss each fall. Some bent down pegged and covered.

Some survived for a time until age and the 2 weeks it took clear caught up with me so let mother nature’s jury decide. 15 years later, other than for 2 or 3 great hardiness finds, all others died ... still pulling out the dead rootstock.

To me, wind dryness etc are contributors to cases of marginals, but l favour believing cold kills major step outs in zone plantings.

You being in USDA 6 (7 CDN) probably are well set to hop a zone or two with tenders with protection used by like zone and minded planters. I still grow few tenders (ogrs) again but limit numbers and only for pollen contribution and sometimes as mothers. Back to using peat moss and bending canes. Good luck.

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Re: Handling cold-hardiness

Post: # 71771Post mntlover
Thu Jul 02, 2020 4:22 pm

This is a subject I have wondered about a lot.Where we were growing roses we did not get below -20 F. On the map it is shown as a zone 5. But there was wind, which was colder. Also a factor I believe was chief in contribution, was how dry the cold air was. I would mound a foot of compost, straw, or dirt up around the plants. When we got some snow I would shovel up a foot or two of snow on top of that. We still lost most of our zone 5 roses. Some of the zone 4 roses survived, but not too well. Only a few varieties from Canada and some hybrid rugosas would have canes that survived.
Surely the temperature wasn't the contributing factor: there were winters where we didn't see -10 F.
Anyway, I would be interested in hearing from others as well.

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Location: Mayne Island BC, Z8. Warmish dry summers, cool wet winters.

Re: Handling cold-hardiness

Post: # 71774Post donaldvancouver
Thu Jul 02, 2020 10:54 pm

Hi- I agree that there is more to hardiness than cold tolerance. There is Zone 3 with constant deep snow cover, and Zone 3 with freeze/thaw cycles, drying winds, drought, bare ground, and so on. This is why a place like Calgary is so challenging for gardeners; on pape it's not that cold, but there's more to it than just the minimum winter temperature.
This is true for warm areas, too: "Zone 8" doesn't really describe a climate. We're Zone 8 here, with cool wet winters and mild dry summers; never hot, never cold. Other Zone 8 regions get blistering hot in the summer. Not the same environment for roses.
I'm not sure what the solution is. The hardiness zone designation is useful, it's just not complete.
Zone 8, with warm dry summers, cool wet winters. Southern Gulf Islands, BC

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Re: Handling cold-hardiness

Post: # 71775Post rikuhelin1
Fri Jul 03, 2020 12:23 am

Might help to agree on defining hardy to a zone before one gets into arguing between 2nd and 3rd order parameter influences other than cold will kill an unprotected tea. Crown hardy or partially cane hardy does not work for me - reminds of too many disappointments - cane hardy to bloom does work most of the time for me as a guide . This year for the first time some 50% of my Suzannes, Carlos Red, White Star of Finland and other spino hybrids had to be cropped right down to just above the above ground based crown - not going to say they are not hardy to zone 3 to 4 a ... a 3rd parameter did it ... canes to old to rejuvenate after cold left.

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Re: Handling cold-hardiness

Post: # 71779Post rikuhelin1
Fri Jul 03, 2020 12:34 pm

Btw, did enjoy last night watching Monty Don O.B.E. bemoaning on gardeners world, with his stoic demeanour, the tree fatalities at LongMeadow in the winter of 2017-18 from snow and one night at -14C ... figs l think or prunus.

Reminded me of St Michael’s mountain succulent rockery looking like it took a beating after that same winter (replanting was in progress) but Alberta’s prickly pear example was doing great - go rid of mine due to too many lancet stabs.

Karl K
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Re: Handling cold-hardiness

Post: # 71786Post Karl K
Fri Jul 03, 2020 7:23 pm

Breeding for hardiness:

Early to bed …
Bugnet: The Search for Total Hardiness (1941)
"I have often noticed that half-hardy plum or apple trees here, unhurt by December 1, passed unharmed through the rest of the winter no matter how intense the cold.

Late to rise …
Rosen: Resistance to Spring Freezes (1956)
"In general those varieties which have an inherent tendency to break their dormancy ahead of other varieties are apt to suffer more from late spring frosts and freezes."
http://bulbnrose.x10.mx/Roses/breeding/ ... pring.html

And grow slowly at low temperatures.
Risley: Male Controls Sprouting (1958)
http://bulbnrose.x10.mx/Roses/breeding/ ... t1958.html

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Re: Handling cold-hardiness

Post: # 71790Post rikuhelin1
Fri Jul 03, 2020 10:47 pm

Txs for posting ... there still hope for Suzanne x Gertrude. Jekyll, and a couple of others hardy x not hardy as at 120 and nada, but no fungus or rot l notice.

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Joined: Mon Jan 28, 2013 8:49 pm

Re: Handling cold-hardiness

Post: # 71791Post MidAtlas
Fri Jul 03, 2020 11:04 pm

Cane disease can be a major problem under certain circumstances (causing cane loss under normal exposure conditions in warmer zones, or in northern areas where there is winter protection applied, or even sometimes under natural snow cover).

There is also an erratic winter dieback problem that occurs most often in R. rugosa hybrids (Explorer Series and otherwise). It seems to be mostly independent of absolute winter low temperatures, but I haven't figured it out yet. I've observed it happening pretty regularly with roses in Minnesota. There may be something about their Asian species ancestry that reacts badly to wintertime temperature fluctuations, inadequate acclimation to cold during fall/early winter, or excess winter wetness--or some combination of those.


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Re: Handling cold-hardiness

Post: # 71793Post rikuhelin1
Sat Jul 04, 2020 12:02 pm

Agree completely Stefan ... seen both cases and latter too many times to count ... the former with some examples of the “ super “ hardies for the first time this year - that l chalk up to cane age as some are nearly, or over, a decade old and some 15 years. Agathas no problems in north garden, (planted in 07 l believe) just minor cane invigoration done on one.

Explorers continue to be a disappointment but not advertised as zone 3. Conclude not liking my garden and climate ... to even be crown hardy ... nearly all deceased except for a couple of small stature 15 year plus old timers who gone through die down cycles (eg Baffin, Frobisher). Some rugosa hybrids like the pavement series dieback is common place in my garden but comeback like nothing happened.

Mordens for the most part are partially cane hardy and definitely crown hardy except for some early efforts that usually have no problems (“Prairie Dawn”). ... Mind you one PD cropped 6inches this year like a herbaceous perennial due to, too slow leaf out (leaves stunted and too slow a crawl up cane to be normal), other example at 6 to 8 feet and blooming like it should - my pseudo hardy climber.

Of course would not do not to include the sam slick caveat “ones mileage may vary”.

Planted an Okanagan raised? monster sized and priced Winnipeg Parks this spring with the other half dozen or so examples (sentimental favourite that will be thrashed in a couple of winters but will be still going on).

Karl K
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Joined: Sat Jun 02, 2012 4:49 pm

Re: Handling cold-hardiness

Post: # 71827Post Karl K
Wed Jul 08, 2020 4:11 pm

I live in the low desert in southern California. Cold hardiness is not an issue here, but the subject still fascinates me.

I remembered one of Percy Wright's non-rose experiments that may be worth a trial. I can't do it down here, but maybe someone in the north would give it a shot. Simply stated, Wright grafted branches of a super-hardy Saskatchewan plum into the crown of his peach trees. Trees that had not been grafted died during winter. Only the grafted trees survived.

Bernie Nikolai (1994) of Edmonton, Alberta added another twist with a "sandwich" of super-hardy / relatively tender / super-hardy.
The “secret” method is top working the tender variety to a prairie hardy tree. Studies have repeatedly demonstrated the least hardy parts of a tree are the roots, the lower trunk, and the crotch angle of branches where they come out of the main trunk. If you bypass these tender-portions by grafting the tender varieties onto the hardy frame tree branches about six to twelve inches or so from where they come out of the main trunk (on a Dolgo Crab, for example), you may be astonished as to what will survive and produce for you if you live in a cold climate.
https://www.apfga.org/increasing-apple- ... s-to-40-f/

I don't know how useful the last bit might be for rose growers, but it does seem like a good idea to use a rootstock that is sure to respond to whatever chemical message the super-hardy tip grafts might be sending down. And then the "somewhat tender" varieties might be preserved for breeding to the more reliably hardy types.

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