ARS Magazine, May-June, 1933
Hybridizing Species Roses
J. H. NICOLAS

HYBRIDIZING species roses has for its object not the improvement of the species, but the improvement of our garden roses through the species. Very few species are worth retaining in their tout ensemble. Their plant-habit is not desirable; after their short bloom season, however interesting it may be, the shrubs are not handsome, the foliage generally being unsightly, especially among the hardy species. If everblooming, improved shrubs could be produced, these might be interesting and they may come in the trail of our hunt for improved garden or bedding roses. The main use of species is as a means to "fortify" (as wine-makers say) our weaker strains, mainly the Hybrid Teas, on which we have to fall back for elegance and beauty of bloom. To infuse enough of the species robustness and "arcticness," while retaining the Hybrid Tea type, is the practical line of march, and a long trek it is!

As in anything else, we want to proceed methodically. The season opens with the wild species roses, and this interesting material must not be overlooked, as hybridization of species is the most fascinating pastime, and the possibilities are innumerable, insofar as "civilizing" and blending them into existing types of garden roses is concerned. Hugonis, Ecae; the various forms and hybrids of Rugosa, Moyesi, Xanthina, Altaica; the Austrian Briars, Persian and Harison's Yellows and Austrian Copper; the American native roses, Acicularis, Blanda, Carolina, Lucida, Nutkana, etc.—all will be a riot of colors in May, and Setigera (the Prairie Rose) in late June and July.

One need not have a large collection of species, as they can be used as pollen parents and for such, a few blooms procured from public parks, arboretums, private collections, and other places where rose species are featured, can be used. This pollen is applied to proved seed-bearing Hybrid Teas. Few, if any, Hybrid Teas are in bloom as early as the species, and they will have to be pot plants brought to bloom either in a frame or under glass. Your friend, the florist, will let you put a few pots in his greenhouse until time to plant them outdoors. A small lean-to greenhouse on the south side of the house is not very expensive and would be a wonderful laboratory or "play-house" the year around. Then pollen can be preserved for some time, at any rate until the first Hybrid Teas (or climbers, if these are considered) come to bloom. Pick the pollen blooms, placing them in a box in a dry place. Do not handle or shake them until time to use.

Hybridizing species is different from crossing horticultural varieties. The results are slower as it is more difficult to make a "dent" into the extremely dominant, refractory character of the species, and it will take long, patient efforts to "tame the shrew" and refine it to the point where it will graduate from a wilding to a finished garden rose. In the meantime, interesting "mongrels" and "chimeras" will show at the first generation, and some of the desirable hybrids will be sterile (like Agnes and Vanguard, the new yellow and orange Rugosa hybrids). For the first cross, the selection of the mate has no importance beyond being a good progenitor, as its part in the game is only to "crack" the species. When the time comes to breed the next or first generation of seedlings, one must be more particular, as the influence of the mate will be more forceful. In my work, I generally select the most prolific and continuous bloomer among the Hybrid Teas, regardless of color and fullness of bloom, my main object being to acquire remontance (blooming more than once). The second generation will show definite hybrid types, some being remontant, and on these remontant types I begin to "build" the bloom by careful selection of mates. If we want to retain much of the hardiness or some particular character of the species, its ratio to Hybrid Tea should not be less than one to three or four at the most, depending upon the natural hardiness of the species. Rugosa, for instance, would be considerably weakened and almost eliminated if the ratio goes below one to four.

As to the use of sexes in species hybridizing, I prefer to use the species as pollen parent. Species, probably because of disparity of chromosome numbers, often resent foreign pollen, and many bear seeds with their own pollen only, while their pollen is generally potent on any fertile Hybrid Tea. Then, the problem of germination is a vital one. While Hybrid Teas, as a rule, germinate readily, species seeds are slower, and some drag along a year or two, or even longer.

Mendel and his interpreters, Drs. Bateson and Hugo de Vries, are silent on the role of the sexes, probably because their experiments have been mainly with simple species for both parents, while in horticultural practice a species is generally crossed with a hybrid; but Dr. Blackburn believes that results should be the same whichever sex of a species is used when crossed with a hybrid. However, my experiences of many years concur with Mallerin's of France, Lambert's of Germany, Dot's of Spain, and other practitioners, that the species is more easily and quickly "cracked" when used as pollen parent; its imprint at the first generation is generally more subdued, or to be more correct, the percentage of the mother type, with, of course, a more or less pronounced species influence, will be much larger than the species type, and these mother types will save time in bringing the desired finished product. For instance, a cross of Hortulanus Budde x R. Moyesi gave me slightly modified Hybrid Tea types where Moyesi was only recognized by the weird red single blooms and smaller foliage, while one almost totally mother type revealed the pollen parent only by the queer bottle shape of Moyesi fruits. The reciprocal cross (R. Moyesi x Hortulanus Budde) produced plants almost as uncouth and crude as Moyesi. The same result was obtained with other species crosses, the only exception being a cross of Mrs. E. P. Thom x R. baltica pollen, which gave one seedling very dominantly Mrs. E. P. Thom, although with smaller foliage, but double, with bloom-color and remontance of Thom, one true intermediate but not remontant, and one almost identical to the species.

*Presumably Schoener's Nutkana

Crosses of species roses and Hybrid Teas sometimes give strange results not always compatible—to the layman's eye —with the parents, but, apparently, they are to be expected when unrelated or distant types are cross-bred: A friend of mine [Schoener] sent me a hybrid reputed to be a cross of R. nutkana and Paul Neyron*, a shrubby, vigorous plant but without apparent trace of Nutkana, although the bloom was single and pink. As it excited a great deal of skepticism as to its true origin, I planted a handful of selfed seeds, and in the lot came several more or less Nutkana types, and one almost pure Nutkana in all particulars, even with its root-stolons traveling long distances. This experience satisfied the doubting Thomases—including myself. Another example of the unexpected: A seedling of Royal Red, a rather low-growing Hybrid Tea, with very large, double, fragrant, deep maroon bloom, and R. oxyodon, a medium sized shrub with thin wood and small foliage. This seedling is an extremely vigorous plant, sending heavy, "lumbering" canes 10 feet high; the foliage is, perhaps, the largest Hybrid Tea foliage known; its red blooms, medium to large and semi-double, come in bunches like the pollen parent. Rosa kurdistana from Kurdistan mountains of northwestern Persia, is a small shrub, seldom over 3 feet high, with medium-sized foliage like R. canina to which group it belongs; pollenized with Miss C. E. van Rossem, a very low-growing Bengal hybrid, it gave a seedling of most gigantic proportion, with heavy canes a half inch in diameter, growing 8 to 10 feet high in a season, with very large foliage, blooming only once, but becoming a beautiful maze of medium-sized double, light pink blooms (Kurdestana is white; Miss C. E. van Rossem, red). Where do these extraordinary changes come from and why? I know the crosses went over as other seedlings of the same hips were true intermediates.