RHA Newsletter 6(2): 6. Summer 1975
Breeding Yellows

Percy H. Wright

Saskatchewan, Canada

The article by Paul Jerabek in the RHA Newsletter of Spring, 1975, was of extreme interest. It was surprising to read that yellow roses in general lack hardiness. Since the source of their yellow color is a gene or genes inherited from Persian Yellow, which is reasonably hardy here in Central Saskatchewan, one would have expected the yellow roses or Pernetianas to be a bit hardier than most hybrid teas. Their susceptibility to blackspot probably comes from a gene in the same chromosome which is not too distant from the gene for yellowness.

My yellow rose Hazeldean was originated by putting pollen of Persian Yellow on the "Scotch" rose, the subspecies Altaica, which normally blooms a week or more before Persian Yellow does. I was able to make the cross by bringing in pollen from a southern source. The flowers of Hazeldean vary a good deal in size, but the larger ones are a bit larger than the flowers of Persian Yellow, and I consider them of better form and certainly of better scent. They are sufficiently fertile that in some years about one flower in ten will set seed. The pollen is much, much more fertile than that of Persian Yellow.

The important feature of Hazeldean is that it is completely free of blackspot, and this suggests that a new race of yellow roses, like the Pernetianas but free of blackspot could probably be raised from it. Such a project would be long drawn out, for one would get once-bloomers in the first generation, and probably not all of the color. My experience has been with the use of Hazeldean pollen on hardy roses and suggests that the chance of bringing down the full color is rather small but it is also a rare chance that brings down yellow color from Persian Yellow. Of the sisters to Hazeldean that I raised at the same time, only one, a single, had yellowness equal to Hazeldean, and its yellow fades. The yellow of Hazeldean is quite sun-resistant.

By the way, the yellow in the Peace petals is not at all sun worthy. Last year it bloomed for me in the bright sun, and there was scarcely a trace of yellow. Flowers that bloomed just before frost, when the weather was cooler and the sun less intense, had more yellow, and a flower that bloomed for me in January this year was almost a rich yellow. I was amazed at the amount. I consider that non-fading of the yellow color is highly important, even more important, perhaps, than its intensity. It is fortunate that the yellow of Persian Yellow does not fade quickly, even in the bright sun.

I recall no mention of non-fading in the two items on yellow roses that appeared in the Newsletter for Spring, 1975. Perhaps another discussion of this valuable feature would be contributed by someone who lives in the milder area where the growing of hybrid teas is easier than it is here on the Canadian prairies.

I do not wish to leave the impression that to originate a new group of yellow roses from Hazeldean would be an easy task, but the prospect of complete resistance to blackspot and greater hardiness too has its own attraction. My guess is that one would need at least five generations and 1000 seedlings in each generation to attain the objective. By the way, I have never seen mildew on Rosa altaica either, though I doubt if it is completely resistant. The best source of resistance appears to lie in Rosa laxa alba.