American Rose Annual 43: 43-44 (1936)
100 Per Cent Thornless Roses
Dr. Niels E. Hansen
State College, Brookings, South Dakota

EDITOR’S NOTE.—In this report of progress at the South Dakota State Rose Garden, Sioux Falls, S.D., Dr. Hansen, an indefatigable worker for hardy roses, goes another long step forward in his development of thornless roses. In the 1927 Annual, details were published of his series of very hardy roses suited to the “cold Northwest.”

IN THE fall of 1932 the work with several hundred varieties of roses had come to a climax. The hardiness had been determined. I had originated some good hardy hybrid roses, especially of the Rugosa type. But after surveying the work, not only at Brookings but in many countries of the world, it was easy to see that it would be impossible for me to excel, or even equal, the marvelous achievements of the rose-breeders of the world who did not have to fight severe winter cold.

I decided that the only way for me to make a definite contribution to rose-breeding was to eliminate the thorns, not only thorns on the wood, but also the bristles on the rachis or midrib of the leaf. This one character that been overlooked largely by the rose-breeders. Hence, in twenty acres of seedlings at Sioux Falls and here at State College, Brookings, every plant was carefully examined from the standpoint of thorns and bristles. A few plants that were 100 per cent smooth were saved. Then the plants were all removed from the State Rose Garden at Sioux Falls. They made a grand bonfire!

In 1933 the garden was summer-fallowed throughout the season to get rid of the roots. In 1934 the plantings began again. This season was the hottest and driest in our history. However, by irrigation the plants were pulled through the season in fair condition, and the past season, 1935, they made a good growth.

In this work I have found it quite easy to obtain smooth stems, some years having over 5,000 plants, but when I determined to go further and eliminate the bristles from the rachis or midrib of the leaf, the difficulty of the work was increased greatly. I had to burn all except a very few plants.

Now I have many hundreds of these 100 per cent smooth-stemmed roses, the flowers single and pink. When I first looked at the problem, I determined that it was necessary to work at only one thing at a time, and to make this thornless character dominant. It would then be possible to breed this to many other varieties of roses and acquire the double flower, other colors, the everblooming habit, and any other desirable character.

Thousands of blossoms are hybridized every year. This work is done mainly at State College by using tubbed plants. They are taken care of along with the large movable orchard of tubbed fruit trees which I keep in the cellar during the winter, remove to the greenhouse after the first of January, and later transfer to the orchard tub-yard, where they remain until fall.

I returned October 19, 1934, from a four-months tour to East Siberia at the invitation of the Russian Soviet government. My son, Carl A. Hansen, was technical assistant during the tour. I studied the rose problem during this tour of agricultural exploration to Russia, but I did not find any thornless roses. However, I found Rosa rugosa and peonies growing wild.

I have studied the rose problem as a side-line in my eight tours of agricultural exploration. As far as possible, I have imported everything in the way of thornless roses from Europe. But many of these “thornless” varieties have scattered thorns which are annoying, especially when hooked, and most of them have bristles on the rachis. Of these, Mme. Sancy de Parabère, and the old English variety, Amadis, are completely thornless. But we want a larger range of color.

It will probably be best to place my 100 per cent thornless hardy roses in the hands of rose-breeders elsewhere with greater facilities in the way of cultivated varieties. The main thing  now is to get the hybridization done as quickly as possible, so that the new varieties will be the ideal 100 per cent thornless. Ultimately they should replace most of the resent list of roses with their abundant thorns. But of even greater importance here in the prairie Northwest, is that of winter hardiness. Hardy thornless roses understocks are also under consideration.

During the past season here at Brookings, more than one hundred new hybrid seedling roses were marked for further attention and propagation. So I am encouraged to believe we can get semi-double and double roses of complete winter hardiness, and that the thorns and bristles will in time be only a memory.