American Rose Annual 79: 79-21 (1940)
Progress in Thornless Roses
Dr. Niels E. Hansen,
State College, Brookings, South Dakota

Since my paper “100 Per Cent Thornless Roses” was printed in the 1936 American Rose Annual progress has been made. The work is mainly with Rosa blanda as collected in South Dakota, western and northwestern Minnesota, North Dakota, and Manitoba. In many thousands of miles of field travel I have found it very difficult to get pure thornless plants because roses hybridize readily. The thorns often persist toward the base of the old stems. Also, bristles on the rachis or midrib of the leaf are annoying.

Much hybridized rose seed was harvested from the breeding experiments in 1938 and 1939. The rose-breeding experiments are carried on with a Federal appropriation; the land is furnished by the state.

The nurserymen of America who bud some twenty-five million roses annually would like hardy smooth-wooded stocks. To originate such stocks is also a part of the work.

In 1937, out of 11,053 seedlings of these 100 per cent thornless roses, 613 seedlings, or about 5 1/2 percent, were entirely smooth, even the first year from seed. The hope is, to make this character come true to seed, and that it will be a dominant homozygote in hybridization with standard double roses.

The South Dakota State Rose-Garden is located at Sioux Falls. Here and at Brookings some twenty acres are devoted to originating roses that will be hardy without winter protection, while at the same time originating hardy thornless rose stocks. (The American Rose Annual, with its thousands of readers in America and many foreign lands, has emphasized the fact that South Dakota is first to have a truly State Rose-Garden.)

In clearing twenty acres of rose seedlings in 1932 for the State Rose-Garden at Sioux Falls and at State College, a few 100 per cent thornless rose plants were selected for further work. Both leaves and wood are smooth. These were introduced in 1936. The flowers are single, pink, fragrant. The abundant red rose-hips in autumn and winter are noteworthy. The plants are of sturdy, upright habit. These plants are now being crossed with many large double-flowered varieties in other colors. In its present condition the strain provides a pleasing ornamental shrub that will endure -50° Fahr. without protection, and which may be found useful by the rose-breeders in eliminating thorns. Not only must the eventual varieties be thornless, as are Amadis, Mme. Sancy de Parabère, Kathleen Harrop, and Marguerite Guillard, but they must be hardy to -50° or -60° without protection. Of course, good fragrance and pleasing color and form are also essential.

A large number of hybrid roses of twelve or more petals are saved for back crosses and for new crosses. Evidently it will be a long step-by-step journey up the mountainside, but we are making progress. Indeed the progress in hardy roses at this station was recognized June 29, 1936, at the annual meeting of the American Rose Society at Des Moines, Iowa, in awarding me First Prize for 41 new seedlings. The leading rose in this collection is named Lillian Gibson. See plate facing page 167.

Lillian Gibson was introduced in 1938. Its pedigree includes: Rosa blanda, from Wilton, northern Minnesota x Red Star (a red Hybrid Tea) pollen. This rose was the sensation at the Sioux Falls Flower Show, June, 1938. The flowers are large, double, with over forty petals of a beautiful lively rose-pink, about three inches across, and with delightful rich fragrance. The plant, of strong, upright, sturdy growth, is a very abundant bloomer in late June; sparsely thorny on young shoots, with scattered thorns on the old shoots. A root sprout of this rose, planted spring 1938, bore 31 flowers the next year.

*Since sending this report, Dr. Hansen provides description of another new rose, as follows: “Yawa. (N. E. Hansen, 1940). A sister to Pax Iola (Anci Böhm [a red multiflora from Czecho-Slovakia] x Rosa blanda pollen from Bimidji, Minn.). (Yawa is the Sioux Indian word for “esteem.”) Not a Pax rose, as the main stem is thorny, especially near the base; but all the side shoots are smooth or nearly so. A tall, wide-spreading, open-habit pillar rose, to nine feet. A very free bloomer in June and early July. Fragrant flowers of delightful light coral-pink, quite double (58 petals), 2 inches across, in clusters from 4 to 12, on the side shoots, with 8 to 12-stems. A good rose for corsages or small bouquets. Apparently no seed-hips are formed, indicating that in such combinations the Pax or thornless character must be obtained in the first cross. Perhaps the pollen will be useful.”

Three varieties of what I am glad to call Pax roses were introduced in the spring of 1938. Pax is the Latin for peace, and thorns are no more necessary in roses than war is among humans! These Pax roses are nearly or quite thornless.*

Pax Amanda. (Frau Georg von Simson, a European Multiflora climber x Rosa blanda from Wilton, Minn.) A gorgeous bloomer of semi-double flowers, about 17 petals, of light pink, turning white. Plant strong grower, with dark brown 7-foot stems, smooth save for a very few thorns near the ground; leaf midrib bristly.

Pax Apollo. Rosa sempervirens pallida x pollen of R. blanda from southern Manitoba. A wonderful producer of deep pink flowers in large clusters in June. Petals about 14. Tall, upright, 7-foot, dark red stems; the wood is smooth; on strong shoots the midrib of the leaf is bristly.

Pax Iola. Anci Böhm (a climbing rose from Europe) x pollen of R. blanda from Bemidji, Minn. Flowers semi-double, clear shell-pink. A strong grower, evidently of the pillar type. The shoots close to the ground also full of bloom. Hundreds of flowers, about 25 petals, 2 1/4 inches across, in large clusters. The older flowers are nearly white; these two colors make the bush a thing of beauty. The strong stems are all smooth; the rachis or midrib of the leaf is bristly, but a pleasing thornless bouquet can be cut from the side shoots.

I never hope to originate any rose more beautiful than those now in cultivation. But I hope to get some good double thornless roses, and to give the propagators smooth stocks for greater safety in propagation, as well as entire hardiness.

Seeking for more far northern material in the fall of 1938, I visited Fort McMurray in Alberta, Canada, 300 miles north of Edmonton, and about 534 miles north of the boundary. The minimum winter record here is -70° Fahr. Plenty of wild game; many airplanes every day en route from Edmonton to the far Arctic north, transporting radium and other ores.

Here the wild roses were all thorny, but I collected other plants, including red raspberries and a thornless gooseberry, which I expect will be hear from later.

In the 1939 importations some thornless selections of Rosa canina were received from Germany. These are for understocks. Whether they will help in rose-breeding remains to be seen. In the 1936 report I said this species is “facultatively apomictical,” (C. C. Hurst), which means that, like peaches, they are often independent of the pollen used. They may set seed without it, according to Major Hurst.

My own experience indicates that stronger hybrid vigor comes from the pure species. According to Hurst, over 80 per cent of the rose species are of hybrid origin.

My method of approach might be termed the geographical one. The botanical name is not enough. In fact, it is often that the choice simmers down to one single plant. That is why field selections are so important. To get winter hardiness, I use the northern type; for summer-heat hardiness, the southern type is best. A species varies greatly within its natural range, but sometimes proves widely adaptable.

I have much faith in the pure native species. In working with the native American crab-apple, the back cross with the tame apple produced, in 1939, fruit 3 1/4 inches in diameter.

In many acres of the native bushcherry, Prunus Besseyi, two plants in 1939 produced fruit nearly 1 inch in diameter. The lowest pit-to-fruit ratio was 3.92, which means that out of 100 pounds of fruit a little less than 4 would be pit. The quality is good and the sauce is excellent.

I wish the roses were as easy to tame as the fruits!

It is a real delight to study the roses of the world, as described in Miss Willmott’s “The Genus Rosa.” In this monumental work the following is of special interest:

Rosa blanda is generally found in damp, rocky situations; it ranges from Labrador, Canada, and the northern United States, across the continent to Vancouver Island. The flowers, which are sweet-scented, are large and a rich pink in color. The hips do not last so long on the bushes as those of Rosa Carolina and Rosa humilis, and are not so bright in color, but it is a pretty rose, one of the earliest to flower, and altogether well worth growing. Its forms are infinite, and are a source of endless bewilderment to amateurs who attempt to determine their wild Roses.” … “In North America it is extremely difficult to draw the line between forms of Rosa acicularis and Rosa blanda.”

Editor McFarland has stressed the need of recurrent bloom in roses—we need the flowers throughout the season until frost. This idea is kept in mind also. I have one seedling with tall, erect stems 7 to 8 feet tall with double flowers of a rich bright pink, appearing freely from June till the end of the season. The first week in October, 1939, when stopped by frost, there were many young buds. The plant is perfectly hardy without protection, and of strong growth. It is a seedling of Red Star, a red Hybrid Tea. The pollen used was my Pink Semi, a selection of the Rosa laxa Retz which I brought from Semipalatinsk, west Siberia, in 1913. But this hybrid sets no seed, and my standard now is no thorns. If we all keep on, the thorns will drop off with the black-spot liability.