My Answers and My Questions on Hybridizing
MY ANSWERS
Choose parents you love. That way, you’ll be especially excited to see the progeny and they’re more likely to have characteristics you value. For example, I love hybrid-tea form, disease resistance so I needn’t spray, compactness so it’s less hassle to plant or care for, and dense, ideally glossy foliage so it looks good even when not in bloom.
So I’ve picked parents with as many of those characteristics as possible. For example, I use Oso Easy Italian Ice x Rainbow’s End. (That cross has produced quality seedlings. From males, I remove the stamens (which, by the next day will release the pollen) and put them in wide-mouthed baby food jars, labeled, of course. I use wide-mouth so that it’s easy to get the pollen onto my finger. With females, with my fingernail, I remove the stamens to avoid self-pollination and a day later*and to ensure pollination, the day after that, I use my finger to gently put pollen of my chosen male on the female’s stigma. I don’t bother with covering crosses with a paper cone — It’s too unlikely that bees will drop pollen from some other rose onto a flower whose petals have been removed.
I avoid having to label each hip by, in the first flush of blooms, pollinating with a male of which I have enough pollen and then, later in the season, pollinating the plant with a different pollen. Thus I know that the hips that mature early are from the first male parent. Note: I record the males’ names on a [wide plastic stake label using a [#6B pencil, which writes thin and dark and unlike felt-tipped markers, won’t fade.
Starting in September (Of course, it will vary with your climate — I’m in Oakland, CA), I harvest each cross when the hip is part orange or red but still is part green. That avoids a too-thick pericarp (the seed’s hard outer shell), which would reduce or delay germination.
I put hips from each cross in a separate baggie, which I label with the parents’ names, for example, Oso Easy Italian Ice x Rainbow’s End. I put the baggie in the refrigerator’s lowest section so it’s near-freezing — That simulates winter, which is necessary for rose seeds to germinate. Around New Year, I remove the seeds from each hip using a paring knife and my fingernails, and plant the seeds roughly an inch apart in a standard flat filling it Miracle-Gro Moisture Control potting soil to which I’ve mixed 10%[perlite to ensure good drainage and root adherence, and minimize dampoff.
I put the flats in a part-sun location, noting which cross is in each flat or part-flat. When a flat has significant germination, I move it to a sunny location. In a Word file, I note germination rates for each cross — simply good or bad.
I never spray with pesticide or fungicide — I’m only interested in growing, let alone trying to commercialize, roses that do well without spraying. Because I live in the San Francisco Bay Area, which has low humidity and thus gets little blackspot, to assess a cultivar’s viability nationwide, I induce blackspot by, in early evening, spraying the leaves with water that has been soaking blackspotted leaves.
I cull ruthlessly. By Mother’s Day, my approximately 400 seedlings are down to maybe 50: I’ve ditched any with fewer than a dozen petals, have poor vigor, or of course, has any mildew or blackspot. At that point, I transplant each survivor into a deep 4" or 6" pot (Remember, they’re compact roses) and insert one of the aforementioned wide plant label stakes, on which I regularly write notes about its performance using that 6B pencil. By October, I’ve culled to the one to three best. I make cuttings of those for further testing here or if I’m really excited about one, I ask a few national rose nurseries if they’d like me to send them cuttings for testing.
In said Word file, I note which crosses did well enough — both in germination and seedling quality — to justify making more of those crosses next year.
Dear reader, I fear that this leaves too much unanswered. If you have questions, feel free to email me at mnemko@gmail.com
Questions
My germination rate averages just 15 percent and some other rose hybridizers get 20 to 30 percent, so I have questions:
Before planting, should I reduce dampoff and other fungal risk by dunking the seeds in a weak Clorox solution? If so, what dilution and for how long?
At what point in the growing season should I cut back on the feeding and watering? As of now, I keep them well-watered until all hips have been harvested but stop feeding in August, which is a month before the first hips are ready for harvesting.
Should I be stratifying the seeds in the hip or shell them and then stratify them in moist paper napkins? If the latter, should I dunk the napkin-wrapped seeds in the aforementioned Clorox solution?
I find rose hybridizing to be a restful hobby. I hope these ideas and even my questions will help yours yield more results and pleasure, with less stress.