The American Rose Annual 23: 72-74 (1938)
The "Arcticness" of Various Roses
Percy H. Wright
Wilkie, Saskatchewan, Canada
EDITORS' NOTE.—In the 1937 Annual there was first presented a new plan of rating the quality previously known as hardiness. On page 166 that direct thinking rosarian, the greatly lamented Dr. J. H. Nicolas, proposed a method of mathematical estimation of frost-resistance for which he invented the term "arcticness." Much comment followed. A rosarian of the colder parts of Canada, from whom we have previously heard to advantage, now discusses the matter, presenting important qualifying facts.
THE late Dr. J. H. Nicolas's article on "arcticness" was one of the most interesting in the Annual for 1937. I approved of his invention of the term, and the attempt to get away from the confusion resulting from the very common use of "hardiness" to mean the ability to survive the winter in some particular place, often a comparatively mild one.
However, I was surprised to note how far down in the true scale his 100 per cent appeared; in other words, how little "arcticness" is possessed by the species he chose as representing the utmost in resistance to winter cold. The Arctic or Circumpolar rose, Rosa acicularis, appears in my district of Wilkie, Saskatchewan. It is well to remember, nevertheless, that the strains growing there may not be as hardy as those native in Alaska and the valley of the Mackenzie. If R. acicularis is like R. spinosissima, this variation is to be expected. I have in my garden certain plants of the Scotch rose that have been entirely hardy under my conditions. Even they, however, can scarcely be supposed to be as hardy, or "arctic," as the hardiest strains of R. acicularis, or we should expect to find them alongside the latter in the Far North, flourishing under the aurora borealis.
Dr. Nicolas took -30° F. as the 100 per cent of arcticness. This degree of hardiness is not adequate for a large region in prairie Canada and parts of the adjacent northwestern states. With us, winter temperatures reach -45° F. every season, and often descend considerably lower. In 1936 we experienced -59° F., and 57 consecutive days passed when the thermometer never once lifted above -29° F., either night or day. Roses with the constitution to withstand these lows are indeed a very far cry from the roses from the Southeast so freely used.
The hardy Climbers we in western Canada are breeding must be able to stand -50° F. without harm, if taking down and covering is not to be required. It is interesting to recall that a species which will furnish such hardiness is already in our possession. The Ross Rambler, of which an account was given on page 115 of the 1935 Annual, seems hardy throughout the prairie area, and, in addition, possesses the everblooming quality in greater abundance than does R. rugosa. According to Dr. Nicolas's analysis, we undoubtedly face difficulties in finding something to cross with it which will not bring down the mean beyond our limit of tolerance.
To judge accurately of the constitution of the bush roses is a very difficult matter, for snow covering interferes with their exposure. It is quite possible for roses which would not even withstand Dr. Nicolas's limit of -30° F. when exposed, to be grown with satisfaction anywhere in "the blizzard country." For many species and varieties, the only protection required is to be in the lee of a good hedge, and the same blizzard which makes us feel that we live very near the North Pole will cover them with from 4 to 8 feet of snow. Such an excellent insulator is snow that under such a drift, little as we should expect it, temperatures at the surface of the soil may not go below 10 to 15 degrees of frost the whole winter. In the fall of 1936 1 forgot to take up one of my Hybrid Teas. By great good fortune a heavy snow, with wind, came before there had been any freezing of the ground, and as there were shrubs nearby, it was covered several feet deep. It is still alive and as "perky" as you please.
Another factor which makes difficult the assignment of the various species of rose to a particular degree of arcticness is the varying maturity of the wood at the approach of winter. In Saskatchewan, for instance, R. rubrifolia, hailing from the high Alps, is hardy when we have had a normally dry autumn to promote ripening of the wood. However, if growth continues late, by reason of abundant moisture, and the stems contain a little too much sap when deep frost descends, they may kill back to the snowline, just as would a species with much less reputation for hardiness. It is possible to make a theoretical scale which will show the survival of roses when they are mature, but in short season countries this would be of very little use in practice, for in the Far North no plant which does not receive the proper signals from the shortening of the day, or from some other source, will be in a condition of adequate maturity. For this reason a rose like Doubloons, I am satisfied, will never be hardy here. It may be that their resistance to cold would be good if, by chance, they were mature, but as it is, they are helpless; they never know that winter is coming! Probably any rose with Nutkana blood in it would show even less adaptation here. Nutkana comes from an area where the days become short even sooner than in our latitude, and yet the reduction in the hours of light is followed merely by cool weather, not by intense cold.
Dr. Nicolas's scale is undoubtedly a good guide as to the hardiness of roses under the conditions of Europe and eastern North America. Here, where a dry climate usually promotes early maturity, and where, on the other hand, early maturity is very much required, certain differences appear.
For instance, R. canina is undoubtedly hardier than the 75 per cent given to it according to his scale, or to -15° F. It rarely kills here if below the snowline. Rugosa, which he has placed in the group of 100 per cent arctic roses, behaves exactly the same, killing to the snowline every winter. For all practical purposes, under drought conditions at least, the two species are not far apart in the same group. On the other hand, Multiflora is very far from being equal to Rugosa in hardiness. Hardy roses budded on it sometimes perish from the winter-killing of the stocks below them, but I have never known the same thing to happen to roses on either Rugosa or Canina. The recent successes of Germans and Scandinavians in breeding a little blood of Multiflora into their roses indicates that elsewhere the relationship of hardiness may be very different.
How far the same qualifications apply to Dr. Nicolas's listing of the Austrian Briars in the 90 per cent group, and Austrian Copper and the Scotch roses in the 75 per cent group, I am not sure. These seem to me to be among the hardiest of roses. Persian Yellow and Harison's Yellow frequently come through the winter unscathed, even when they have been deprived of snow covering. Their arcticness is certainly greater than that of either Rugosa or Canina. On the extreme hardiness of certain forms of Spinosissima I have already remarked.
In making up the following addition to Dr. Nicolas's scale, instead of disturbing it at its basis, I am committing the mathematical crime of going above 100 per cent. Let the ability to endure -40° F. be equivalent to 115 per cent arcticness; to endure -50° F. be equivalent to 130 per cent arcticness; and to endure -60° F. be equivalent to 150 per cent arcticness. It will be easy enough to revise the whole scale if necessary to do so.
The following ratings are to be taken as only suggested, and as very much open to correction. To make such a determination, scientific tests would need to be given by removing the snow covering, or in the laboratory. It is not always safe to assume that the hardiness of a species is to be measured by the temperatures of its area, which may have an annual and deep snow cover. Wild raspberries collected in northern Manitoba, for instance, have been found less hardy in the gardens of Ontario and Minnesota than the domesticated varieties commonly grown there. Perhaps the difference may be attributed to the fact that the native Rubus species grow under a forest and not in the open. Evidently species of dwarf plants may penetrate far north of the area fully adapted to them.
|150 per cent||the Circumpolar rose.|
|130 per cent||other northerly species; R. blanda, suffulta, Sayi, Beggeriana, some spinosissimas, and the Ross Rambler.|
|115 per cent||R. rubrifolia, xanthina, foetida, cinnamomea, other spinosissimas.|
|100 per cent||R. rugosa, some canina species, still other spinosissimas, perhaps nitida.|
My experience with the more tender species is not sufficient to suggest any changes farther down in the scale. I heartily wish that someone would undertake to place all the species individually, for then a knowledge of the composition of a new rose would enable us to deduce its probable hardiness. I consider that Dr. Nicolas's suggestion that the arcticness of hybrids ranges between that of their parents was a very valuable contribution to our understanding of roses, and full of implications yet to be worked out. His treatment of the subject in his short article was masterly, full of recognition of its tentative nature and yet with the germ of an important idea, as well as with some most interesting applications.