Rose Magazine 5(4): 68-69 (July-Aug 1943)
Methods of Germinating Rose Seeds
C. A. Davis, Buffalo, N. Y.
Since the beginning of the war, our foreign source of new rose introductions which we have been in the habit of expecting have gradually declined with each occupied country until now there are very few reaching our shores.
We shall miss the charming Polyantha hybrids sent out by the Poulsens of Denmark, the glamorous yellows from Jean Gaujard and Mallerin of France, the new creations by Kordes of Crimson Glory fame, and those of so many other foreign hybridizers who have had to curtail their rose work for the duration.
Fortunately we have some hybridizers in our own country who have given us many fine roses to enjoy and now we must rely on them for our new introductions.
Lately, there seem to be numerous amateurs who have taken up rose breeding, no doubt inspired by prevailing conditions, and have found the work so pleasant and fascinating that they have been searching for more information regarding the subject.
Much has been written about the actual manipulation of cross pollination, with sketches showing the fundamental parts of the flower, how to handle the pollen and make the cross. From here on the information regarding the germination of ease seeds is quite vague and uncertain.
To germinate rose seeds is difficult at heat and to get twenty per cent germination of the total seeds planted is considered good.
Probably there are as many ways of germinating seeds as there are hybridizers and each has his own favorite method, or general method with variations. Some of the methods are planting seeds in pots of special soil or planting in flats, but for the amateur this usually requires more room than he may have at his disposal. Then rose seeds are sometimes stratified in damp peat moss and stored in the refrigerator as suggested by the Boyce-Thompson Institute. I like this method best with certain variations because so many seeds can be after-ripened and germinated in such a small space in the over-crowded refrigerator.
I use four small rectangular pans, nine inches by five inches by one inch deep with close fitting covers. These are partitioned and subdivided into small compartments, the size of which depends on the number of seeds of each cross.
The peat moss is sifted and then sterilized in the oven at 300 degrees Fahrenheit for one hour just to make sure there are no disease germs or insects such as Nematodes, etc. After cooling, I moisten the peat and spread it on the bottom of each compartment about three-eighths of an inch thick. The rose seeds are placed on this carpet of moss with sufficient space between them and then covered with the same amount of damp peat moss. These four pans will store approximately one thousand seeds which after all requires surprisingly little refrigerator space.
My rose seeds are harvested before the first freeze and are planted soon after, however any green hips are given an after-ripening period until they change color to yellow or orange in a shallow bon of damp sand and covered with a pane of glass.
The seed pans are examined once a week and the top layer of moss stirred gently for aeration without touching the seeds. For this I like a pair of tweezers best and they are ideal for lifting germinated seedlings without disturbing the neighboring seeds. After keeping the seeds refrigerated for a few months and sprayed occasionally, they are removed from the refrigerator and held at room temperature. There is quite a flurry of germination during this time. When the flurry is over, back they go into the refrigerator for six weeks, then again at room temperature with subsequent increase in germination. I'm not quite sure if this method of changing seasons affects the seeds, or if they are just naturally ready to germinate. However, it seems to increase the number of seedlings.
There always seem to be certain crosses which you are particularly interested in, a species on a hybrid or some other difficult cross. They seem to be the ones that fail or are very slow to germinate.
After approximately seven mouths of failure to germinate, I give these seeds the "Treatment." This consists of carefully scraping the outer seed coat until the line of cleavage is clearly visible. Then with a dull pocket knife placed along the line of cleavage, carefully press until the seed coat splits in half. You will probably ruin a few seeds until you get the knack but with practice you will become quite proficient in the art of a la Caesarean. The viable embryo is plump and bright straw yellow while the dead embryo is brown and opaque.
It is probably better to leave the embryo on the lower half of the seed coat for support and then put back in the peat moss, cover carefully and keep at room temperature. The embryo so treated will probably germinate in two to six weeks. The method has given ninety per cent germination of viable seeds.
While this method requires more work, I have found it invaluable in bringing about the germination of difficult seeds which after all are the ones most desired.