American Rose Annual, 1947
The Interactions of Various Rose Species
Percy H. Wright
Moose Range, Saskatchewan, Canada

If I had been able to germinate all the artificially pollinated rose seeds I have produced, I might have been an authority on the topic I have selected. I have gotten between 8,000 and 29,000 seeds every year since 1937 except 1941, and yet out of all these, on account of the lack of germination, the expense of planting out, and the care of seedlings needed till blossoming time, I suppose I have not actually bloomed over 3,000. Some 3,000 are now planted out awaiting blooming.

I saw an article in the Rose Annual proposing that intensive work be done on making a chromosome map of Rosa, as has been done for the common fruit fly, and more tentatively, for numerous forms of life. I am all in favor of starting such a project for its value to pure science, if nothing else.

However, I doubt whether the information on dominance and linkage, so obtained, if the work were done within the hybrid tea, hybrid perpetual and polyantha group, would be of much value to breeders whose aim is to strike out into more original lines of effort. May I assume that most authorities will agree with me when I say that it is obvious that the hybrid tea must soon be given new genes, if it is to develop further? The demand for roses like the hybrid teas in flower and general characters, but more disease resistant and a little hardier—even if only a little hardier—must be very great.

I do not know a great deal about the behavior of species when crossed with hybrid teas, for I have produced few seeds of such crosses, and a still smaller number of these germinated. The climate in northern Saskatchewan is very severe. To illustrate, I need only say that the old stand-by, Harison's Yellow, a byword for hardiness and persistence, kills to the snowline every winter, mild or severe, and sometimes below the snowline. This lack of hardiness eliminates for easy growing the hardiest yellow rose. Double Yellow Scotch is less yellow and still less hardy, and Persian Yellow is noticeably less cold resistant. It has been one of my main projects to cross Rosa spinosissima altaica with Harison's Yellow, and thus obtain a hardy yellow rose for the northern parts of the Canadian Midwest. The best I have been able to do so far is a pale lemon, or a flower otherwise about the same as that of Harison's Yellow. I have since backcrossed this rose, which I call Harison's Hardy, with Harison's Yellow, but none of the seedlings have bloomed yet. I suspect none of them will be sufficiently hardy for my district, although they may perhaps be hardier than Harison's Yellow, and hence useful elsewhere.

As a result of the severity of our climate, I have only recently used hybrid tea pollen at all freely, and my work has consisted of interbreeding the hybrid Rugosas and Mr. F. L. Skinner's Betty Bland (an R. blanda hybrid), and several others, with northerly, hardy, or semi-hardy species, as follows: R. altaica, Macouni, suffulta, acicularis, blanda, virginiana, nitida, rubrifolia, gallica, centifolia, multiflora, laxa (R) and rugosa. In addition, I have used the Ross Rambler and Banshee, which are of undetermined species. Here are some of the results obtained:

Rosa rugosa—Rugosa's descendants are likely to have flower stems both short and weak, bristly branches, bushes spreading, sometimes half prostrate, and an excessive susceptibility to the insect that makes galls. The flowers are often quite large. As is well known, crosses with everbloomers tend to be strongly everblooming.

Rosa suffulta—Suffulta is a remarkable species native to the northern great plains and seldom grows over a foot high (although I have one pure strain that will reach 20 inches). It blooms till late fall but only on young laterals that have not yet bloomed. Each lateral blooms only once. When crossed with other northerly species, it gives hybrids that tend to have small to insignificant flowers, which is rather surprising, for the flower of this dwarf rose is very little smaller than that of R. blanda and about the same size as that of R. laxa (R). It tends to suppress the violet tone in its descendants, and in this respect is extremely valuable in breeding. The leaves of the hybrids are small and rather bluish in tone. The height of the plants is intermediate between that of the parents, usually nearer the taller. The fall blooming habit has always been suppressed in the offspring. Even when crossed with a profuse fall bloomer like the Rugosa hybrid Hansa, the fall blooming characteristic disappears. Each apparently suppresses the everblooming of the other.

Rosa blanda—The thornlessness of R. blanda, and the erectness of the growth, its hardiness, and the violet tone of its "wild rose pink," are fairly dominant.

Rosa Macouni—The bushes of the descendants of R. Macouni are far more spreading, and the flower stems shorter and weaker. They have, I believe, a little greater hardiness, and the same tendency toward violet and to rapid fading.

Rosa acicularis—The Arctic rose tends to give its progeny a less profuse blooming habit than either R. blanda or R. Macouni, but considerably more stature, larger leaves, and fairly long flower stems. It is remarkable for the way it transmits hardiness. The hybrids stood -67° F. in the winter of 1942-1943, and were undamaged to the tips.

Rosa virginiana—This gives rather glossy foliage, healthy and attractive, a violet flower of small size, bushy shape, and a tendency to late flowering.

Rosa nitida—The strikingly shiny foliage is strongly persistent in its progeny but the beautiful autumn tints of the foliage are less so. The hips and the flower stems are bristly, and the latter are very slender and often very weak. The whole bush is weak and tends to lie down in a rainstorm. Suckering (close at hand, not especially to a distance) is extremely rapid, and the plants are difficult to keep weeded. On the other hand, the color of the flowers is good, the violet tones being suppressed as in R. suffulta hybrids; and their form, too, tends to be good. R. nitida should be a valuable parent if the linkage of slender, weak stem can be broken.

Rosa laxa (R)—An interesting rose, 100 per cent hardy, and with small, attractive foliage. Its hybrids tend to have small foliage, small flower, and strong, erect growth.

Rosa spinosissima altaica—Very promising as a parent, usually giving hardiness, healthiness, and fair to good size of flower. If I may judge from one example of a cross with the hybrid perpetual Karl Foerster, the flower stems of its descendants with modern roses will be good, both strong and fairly long, and the texture of the petals will be good.

Rosa rubrifolia—The leaf color can be transmitted to descendants with fair ease, but the leaves often lack healthiness and the plants become "leggy" early. The flowers are comparatively free of violet tones, tend to be smallish, and to have white centers. They resist doubleness too well, and sometimes the petals are small, giving a star-like effect to the flower.

Rosa multiflora—Parts with the small size of its flower fairly easily, but much less easily with the small size of its fruit. Seems to make such a combination with the foregoing species that considerable hybrid vigor results. The smooth stem of the thornless form is not hard to transmit.

Harison's Hardy—Resulting from pollen of Harison's Yellow placed on pistils of Rosa spinosissima altaica, The flower is similar to Harison's Yellow in doubleness and size, averaging slightly larger; color a deep cream in the center of the flower and pale cream at the outside. Foliage intermediate. Plant more erect than the pollen parent. Much hardier than Harison's Yellow; hardy to -60° F. Fertile.

Aylsham—Resulting from pollen of Rosa nitida placed on pistils of the Rugosa hybrid Hansa. Stature of plant intermediate between the two parents, stems slender, with a tendency to recumbency. Flower stems slender and weak. Flower a deep pink, approaching red, free of the violet tones of Hansa, very full, with more petals than Hansa, and much tidier in form, a little smaller. Foliage similar to Rosa nitida but larger and with less autumn coloration. Blooms once in June. Completely fertile.

Another principle which has been uncovered is that if a rose of a pure line, that is, a species, is crossed with a complexly hybridized rose, the characters of the pure-line will be dominant. For example, if species A is crossed with species B, and then the hybrid crossed with species C, the resultant progeny may be strikingly uniform and strongly resemble C. On the other band, if A and C were first crossed, then B crossed with the hybrid, the progeny will strongly resemble B. No one, thus, should expect too much in the first generation from crossing a hybrid tea with a species. If the characters of the hybrid teas are to dominate, put their pollen on a hybrid between two or more species.