RHA Newsletter 3(4): 6-7 (1972)
FIGHTING OFF DAMPING-OFF
Saskatoon, Sask. Canada
It was in 1932 that I made my first rose pollinations, and the results of my "beginner's luck" were so exciting that from then on I was "hipped" on rose breeding. From then to the present, I raised approximately 10,000 hybrid seeds in most years, but was so unskillful in germinating my seeds and in protecting my seedlings from damping-off that the percentage of seeds that became flowering plants was disgustingly small.
One year I tried disinfecting my soil in the family oven, but this was a failure. Apparently the completely sterile soil was the ideal "garden" for damping-off organisms that would have at least been checked somewhat by the organisms that the heat had killed.
Another year, I tried mixing a little sulphur-flour with the top soil, a method which I had observed used with outstanding success with pine seedlings. But it didn't work for the rose seedlings. The soil was undoubtedly made a bit acid, and the acidity seemed to inhibit germination, without being particularly inhibiting to the damping-off organisms.
I did not have satisfying success until this year, 1972. I made three changes in my usual method of sowing the seed. First, I no longer placed the seeds directly on top of the soil, then covering with vermiculite. Instead, I put perhaps half an inch of vermiculite on the soil, and sometimes an inch, then placed the seed on this, and covered with another inch of vermiculite.
Second, I arranged for the vessels in which the seedlings were to start to be watered only from the bottom. To do this, I made a frame with one-by-twos, the size of the spaces which would be adequately lighted by my fluorescent fixtures, and placed in this a sheet of polyethylene film to make a shallow basin. Each container has a hole or holes in the bottom, and is sitting in a quarter inch of water about a quarter of the time. The moisture seems to rise in the soil, and from the soil into the vermiculite, well enough to keep the plants growing at their best speed, and yet the surface of the vermiculite is never as moist as if I had watered from the top. The task of watering was much reduced and much simplified, and the danger of overwatering was eliminated.
These two changes in my method were responsible for cutting down my losses from damping-off to practically nil.
The third change I made was interesting, too. In previous years, I had potted up summer plants and put them under the lights also, and aphids and white flies were carried over in these older plants, and soon reduced the vigor of my new seedlings. This year, I left the space under the fluorescent lights completely vacant from about June 15th on. All the "bugs" seemed to die out (from starvation?), and so my new seedlings had a clean start. What a comfort that was!
My containers cost me nothing. I pick up discarded cans that held tomato or orange juice, remove the tops, and make several large holes in the bottom. Then I line the sides inside with a layer of polyethylene film, so that the soil won't stick to the metal. After I sow the seed, I water from the top once, and then tie one piece of film over the top so that it is unnecessary to water again until germination begins.
I am lucky in that the winter temperature of the room in which I store these seeds for their "stratification" period is about 42 degrees F. Most of the germination occurs just when I want it, that is, when the temperature rises to 45 or 50 degrees.