WHEN I read most instructions on the details of how to cross-pollinate rose blossoms, especially if the article is accompanied by a photograph of a neat little kit of instruments, I am amused. One would be given to think that the hybridist is a sort of surgeon, and that there is a cloud of mystery hanging about the simple process he aims to use.
I have been obtaining hybridized seeds in such numbers that it has been impossible to care for more than a small part of them. Beginning with two pollinations in 1932 (one of which was blessedly successful, giving 40 seeds, and my whole start in rose enthusiasm), I gradually worked up to 2,147 seeds in 1937. In 1938 1 topped that again, with over 15,000 seeds. In 1941 the pressure of business brought me down to 6,500 seeds. In all this time I have never used any materials but a sharp jack-knife, some typewriter paper and store string!
In the rose genus, cross-pollinations are easy. It is only the work of a momentprovided that the plants one uses for parents are not too far apart!
First, there is no need to make two jobs of the operation. To emasculate one day, and come around the next, hunt up the exact flowers that were left unfinished, and then apply the alien pollen, is unnecessary care and unnecessary labor. Making a single job of it takes much less time, and is fully efficient. Pollen is viable over a fairly long period of time, as long as it does not mold. The mailing of pollen across half the continent has proved that. I have successfully used rose pollen sent me from Ontario and elsewhere.
Of course, if one is to avoid the danger of self-fertilization, he must emasculate at least a few moments before the pollen is ready to shed. The dangers of self-fertilization are probably exaggerated, for rose varieties may be presumed to be like apple varieties, varying among themselves, but in general giving a rather low catch when forced to depend upon own pollen. I have observed very little self-fertilization in growing on my hybrid seeds, although at times I have come very close to the moment of dehiscence. In the case of Rosa rubrifolia I have repeatedly and in numbers got seedlings which show no evidence of having been descended from foreign pollen, but this may be apomixis (*Reproduction of organisms without previous sexual fusion of cells or nuclei.) Rubrifolia, at least in its state of unbalance of the male and female elements, is one of the Canina group, and all the Caninas are reported as subject to apomixis.
Despite the comparatively small chance of self-fertilization, the careful worker will wish to guard against it. If one notices that the pollen begins to shed as he pokes out the anthers with the point of his knife, it is easy to move on to another flower. What one should carefully guard against is leaving the anthers unremoved, hidden in the petalage.
It is not necessary to observe whether the stigma is in its sticky, receptive condition. All one need do is to catch the bud before its own pollen has dropped, and then to apply the foreign pollen. The state of the anthers is a close enough guide.
Gather the buds that are to serve as male parents at least one day ahead, and bring them indoors away from insect interference. The following day it is not necessary for the petals to have opened. To use, simply tear off the petals, and the little group of anthers remaining, full of pollen dust, will serve as a ready-made brush of the right size, from which pollen may be directly applied to the stigmas of the flower. If this pollen brush is used very lightly at first, there will be enough pollen to serve four or five flowers. One can spin it out even to ten, if he is short of the pollen buds. The pollen will drop in tiny yellow clouds, and it is a pleasure to watch it going on and to dream of the new roses that may spring from the subsequent unions.
Paper bags need not be used. They catch the wind and break off stems and buds. Scribble paper, or typewriter paper, cut into small squares or oblongs will give equally as good results. Cut the paper into sizes about two inches each way, or more, according to the size of the buds to be worked. For instance, Rugosa or Gallica buds will require a much larger wrapper than Lucida or Multiflora. After the pollen has fallen where its work lies awaiting it, simply fold the paper over the bud, and tie it around the base of the ovary with a short piece of string or heavy thread. I have seen no evidence that an airspace under the paper is any gain, but one must be careful not to tie the paper too tightly.
The name of the pollen parent should be written on the edge of the paper that folds over the ovary-hip, where the pencil marks will touch only the stem. If written in the center of the piece of paper, the rotting away of the remnants of the petals may discolor the pencil record. The female parent need not be recordedthe mother plant is before you.
Do not remove the paper covering until the harvest of the hips in the fall. In my dryish climate, at least, the paper covering does not do the slightest harm, and it is much easier to find the hips one has worked with white paper to guide the eye.
In pollinating species roses, or other singles, the flowers open just as the dawning sun warms them up. The best time to pollinate is thus in the evening or very early in the morning. With double roses there is less relationship between the opening of the petals and the receptiveness of the stigmas, and one must experiment for himself. The danger is greater of opening up the flower too soon than too late, especially with the exceedingly double varieties. In fact, about every rose there are certain things which we must find out by experience.
In this far northerly climate I have not pollinated Hybrid Teas. If I did the seeds would not ripen before autumn. Even Gallicas scarcely begin coloring up before deep frost, but Centifolias are more seasonable. The rose that is quickest to ripen its hips, of any that I have tried, is Lucida. Pollinations made in late July, to the 25th and later, have given ripe hips in early September. Some everblooming roses do even better than that, for instance, the Rugosa Schneezwerg. The scrapping of the complicated processes so often advised in making pollinations is a great advantage. One can secure five times as many seeds, in the same hours of work, and the task is pleasanter because it is speedy. Out-of-doors pollinations are much more practicable than greenhouse ones.