HARDY, EVERBLOOMING ROSES — ones which will withstand temperature of -25°F. without injury — have intrigued the imagination of American rose breeders and rose growers alike from the early days of rose culture. With the appearance of each garden class — the Hybrid Tea, the Floribunda, and the Grandiflora — the frontiers of rose culture have been pushed back until there are few localities where roses cannot be grown successfully, providing a certain amount of effort is expended. This is not due to efforts of the hybridizers alone, for an increasing knowledge of plant culture, rose pests, and pesticides has contributed its full share to rose advancement.
The "certain amount of effort" referred to in the preceding paragraph is frequently the deciding factor in determining whether roses or some plant less demanding in its requirements is to be grown. This is especially true of transition zones between areas of climatic extremes. The area lying between the Mississippi and Missouri Rivers is such a zone. In this area drouth, high light intensities, extremes of heat and cold, and continuous winds — hot in summer, cold in winter — impose handicaps difficult to overcome. The larger number of rose plants growing in home gardens bears witness that they can be surmounted. Nevertheless, these handicaps often discourage the beginner and those not inclined to expend the effort necessary to grow roses under such prevailing conditions.
The economic development of areas inimical to rose culture and attendant shift in population provide ample incentive to the rose breeder to develop garden roses with greater to climatic conditions. There is a need for roses with greater cold hardiness, heat tolerance, and resistance to pests. In our view, the factor of cold hardiness should receive major emphasis, while at the same time, the importance of those other qualities inherent in current varieties can not be ignored.
Rose growers are very selective in their rose choices. The breeder must be cognizant of this. Hardiness, fragrance, or any other single factor is not enough to merit continuing sales appeal for any rose. There are roses which boast superior hardiness (see American Rose Annual, 1959, pages 133-138), but they are found only occasionally in gardens. There is no market for June-blooming roses of superior hardiness, regardless of their merit. This is not peculiar to America for Wilhelm Kordes3 says, "...but as they bloom only once who is going to buy them?"
Sources of extreme hardiness in roses for combining with the the tender repeat-flowering garden roses are not plentiful. Logical rose species having this characteristic are those native to areas subject to little winter precipitation, rapidly fluctuating temperatures, and long periods of extreme heat and cold. A list of these specles would include R. blanda of the prairies; R. suffulta of the spring wheat country; R. acicularis, the circumpolar rose; R. spinosissima altaica; and R. beggeriana from central Siberia.
The Iowa State University rose breeding program has concentrated on combining three species — R. blanda, R. laxa of Retzius and R. fedtschenkoana — with garden roses — Hybrid Teas and Floribundas. All of the hardy species listed in a preceding paragraph were used at the start of the project but were discarded when it was found that they contributed little to the progress of the program.
The usual result obtained in the first generation from a cross involving a once-blooming rose, frequently with impaired fertility, bearing a close resemblance to the species parent — the traits of the tender parent being largely masked by those of the hardy species.
If primary hybrids of a hardy species and garden roses are available, they frequently can provide the means to get around these first generation problems and speed up the breeding program. There were two such hybrids of R. blanda available, Lillian Gibson (R. blanda x Red Star) and Betty Bland (R. blanda x unknown Hybrid Perpetual). Lillian Gibson combines the plant characters of its parents in approximately equal proportions.The flowers, which are borne in clusters of 10-20, possess good form, good petalage, and clean color. It is a triploid which produces an abundance of pollen of low viability. Betty Bland shows evidence of its Hybrid Perpetual parent only in the flower — which is twice as large as that of the normal blanda flower — doubleness, and in inhibition of the suckering tendency of the species parent. Under Iowa conditions it produces seed pods which contain few seeds which seldom germinate. Its pollen has good viability. In these progenies the flowers range from single to semi-double in varying lavender-pink tones. Well-shaped blooms are not common, the principle malformation being a conversion of the pistils to leaf-like organs.
Betty Bland has been a better parent than Lillian Gibson, although it leaves much to be desired. (The progeny vary in hardiness according to their other parent). Excerpts from field notes summarize the Betty Bland-hardy rose variety progenies:
Both individuals produce viable pollen, but are poor seed parents. Use of these selections with Hybrid Tea roses as seed parents has produced populations in which the number of repeat-blooming individuals averages 30-45%. Hardiness is yet to be determined.
The Betty Bland-garden rose progenies have been very similar to those from Lillian Gibson. One odd thing about the Betty Bland seedlings: regardless of the seed parent, 5-10% of the seedlings will be repeat-bloomers. The flowers are so malformed as to be more curious than desirable, however, and the plants are totally lacking in hardiness.
Rosa laxa came into the breeding program almost at its inception upon the advice of Dr. F. L. Skinner, who had been using it for several years. Dr. Skinner had made many combinations with this species and types hardy in his latitude and felt that it was a worth while source of breeding material which had, up to that time, not been used. With the emphasis here being upon the production of Hybrid Teas and Floribundas of superior hardiness, the first step was the production of primary hybrids between the species and garden roses. The initial attempts were disappointing. R. laxa failed to set seed with foreign pollen, and when used as a pollen parent, the seed set was disappointingly low. The plants which from these early crosses were either lacking in vigor and or hardiness or extremely vigorous and hardy. In either case the flowers grossly misshapen.
In 1952 R. laxa pollen was used on one of Kordes' Sweetbrier hybrids, Josef Rothmund. One pod matured containing eight seeds which produced five plants. All were very hardy, withstanding -30°F. fully exposed without injury; relatively dwarf, averaging 3-4 feet in height; and very bushy. Four bore single, white flowers and had foliage which was lost by early August. The fifth had semi-double flowers of pale salmon-pink and persistant foliage.
The pollen from this seedling is extremely viable, resulting in combinations with a wide range of seed parents. The seedlings are slow to mature, often requiring three to four years, so that the raising of succeeding generations is a slow process. Two dilutions of Hybrid Tea and Floribunda blood, however, have not appreciably lessened the total hardiness of the laxa-Rothmund parent, while imparting quality to flower and foliage. The repeat-blooming character is appearing in many individuals, and as breeding emphasis is placed upon these, the character should be recovered in increasing numbers.
R. fedschenkoana came into the breeding program in 1955, the plants having been obtained from T. Hilling and Co. of Woking, England. This species promises much. It is very hardy, and when established, flowers continuously, if not profusely, all season. Field notes record open flowers and buds in many stages of development in late October. The early use of this rose as a parent is similar to that of R. laxa. It is almost useless as a seed parent, and its pollen is poor. The seedlings from it to date are vigorous and have the silvery-green foliage of the species. The flowers vary in petalage from 5 to 15 petals. The superior hardiness of the species does not appear to be lessened by the garden rose parent. Unlike the progeny of R. laxa, repeat-flowering individuals have appeared in the first generation.
At the beginning of this breeding program the prospects of producing hardy everblooming roses did not appear promising. These early efforts have been reassuring, however, and have given reason for continued investigation.
Note: The seedlings described in this paper are mentioned only as examples of breeding results and are not available for distribution.