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.
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.
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.
Duane
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.
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.
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.
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. http://bulbnrose.x10.mx/Roses/breeding/Bugnet.html
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/Rosen_Spring.html
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.
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.
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).
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. http://bulbnrose.x10.mx/Heredity/WrightPeach1981.html
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.
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.
Today I happened upon another factor that had not occurred to me. The color of the canes and branches can influence winter hardiness.
There is not mystery to it once we set the stage. Suppose the temperature is hovering about freezing. Sun is shining and branches that are black or brown will be absorbing the solar heat. Any ice in the surface tissues melts. Then a cloud blots out the sun for a little while. The water freezes again. The cloud moves on and the ice melts again. And along comes another cloud. The repetition of freeze-thaw-freeze-thaw wears on the tissues.
Red canes reflect red light (obviously) along with most of the heat. Thus there will be less thawing. This is not a perfect protection, but it contributes to the hardiness we need. White bark, like a birch, would be better, but we make do with what we have.
Another help is wax. Winter winds can be very drying, so a layer of wax protects the canes from desiccation. Clear, glossy wax over red canes would be a winning combination. Or a nearly white layer of wax, like that of ‘Asta von Parpart’ would be nice. http://bulbnrose.x10.mx/Roses/breeding/HarveyHardy1924/HarveyHardy1924.html
Hmmm … may be way down south heavy bottoms refinery wax good idea as according to HMF input good down to US zone 2 and up to zone 8 … definitely not 3a Canadian … tried it and a half dozen or so of his MF crosses and as well waxy imports. Nordlander 1 and 2 marginal.
l was referring to a whimsical guess as to where rather large potted Winnipeg Parks roses were raised that were being offered for sale. Largest l have seen and filling up what l guessed to be 10gallon pot or maybe larger (tub), wasn’t 5 gallon. Longest canes near 3 feet (between 50 tp 60$ CDN). Never seen Morden shrub roses offered at that size.
Okangan Valley is the same as the hot one in the eastern part of your state.
Westbank outside of Kelowna also in the valley and is the home of a large commercial nusery and its growing fields. Product makes it to Alberta.
l caught a sneak peak at hundreds of Oscar Petersons in rows before official release a few tears back.
Ah, I was wondering if you were referring to the Okanogan Valley. We were living in the Okanagan highlands uphill east of the valley. Now relocated a bit south and west in Methow Valley. Just unusual to see the word “Okanagan” as it is rather unique.
Wish I had known about that nursery when we had visited friends up that way. Would have been nice just to see some plants. Not a lot to offer going down the valley on our side of the border.
Duane
Definitely the same valley even if rarely get the right number of “a” s in the name first try - been to it off and on since the 70s.
Use to be big fruit growing valley. In last 25 years converting to gran Crü. The Canadian side from Osoyoos (sic) to past Vernon is densely populated with wineries. Burrowing Owls cabernet Franc is the best I’ve tasted after Italy’s Paleo by Le Machiole (sic). Kelowna is big tourist area for heat deprived Canadians. If ever visit, summer is peak time and traffic will test you.
The nursery is commercial, though it has a small retail outlet with perennials and roses and usual gardening support “stuff”. However never saw rose fields. The rows were rows and rows of 1 and 2 gallon pots of small young small roses newly planted in a large fenced off growing area in front of outlet. The growing fields were full of saplings (fruit, apples, landscaping trees etc). Names Bylands. This year bought a “Calgary” Box having their label and stated good to minus 30C and reminds of the Kentucky blue wisteria also trying this year with claims of good to -30 to - 40c. Paint me skeptical but willing to try.
Number of “a” s may not vary in the name,.unless I type it fast, then it will be whatever comes out of my typing fingers. If I actually stop and think I would get it right every time. Pronouncing it may be worse, but I have found that all over the country with names for places: keeps it interesting I suppose.
There are wineries going in all down the valley from the border to Wenatchee. Not sure about south of that. We didn’t have the heat they had down in the valley, could be like an oven in summer. Tough extreme for roses, given the cold wind off the lake in winter, but quite a few growing around town down there.
Thanks for the info. There are a few small local nurseries around, but not a lot. Not sure there is a lot even in Wenatchee, but I’ll probably check it out this spring. Glad for the internet when it comes to buying roses!
Duane