Dr. Malcolm Manners of Florida Southern College, posted to the Antique Rose Forum on Houzz/Garden Web, the following. So far, only Paul Barden has offered him any advice. If anyone here has more to add, please do! You are welcome to post the response there or here, and I will copy and paste it there giving you credit. Thank you! Malcolm has done a great deal for the “rose cause” as well as the citrus industry, and has collected a wonderful selection of tropicals on the FSC campus.
I have an uncle in Pennsylvania (5B) whose Alba Semiplena is loaded up with hips, and he wants to germinate some seeds. Just wondering if anyone here has had experience with albas – are they easy from seed? Do they need a longer stratification than hybrid roses? Perhaps a double stratification? Any other tips for sprouting them? Thanks.
My suspicion is that they’d benefit from warm stratification first (couple months in moist substrate at room temperature or so) before their cold stratification period, like other Caninae relatives. I had much delayed germination going straight to cold where they then needed to go through the next summer and another cold strat before germination. I have to dig out some old data from years ago where I tried different warm stratification treatments before cold and followed germination after. I may have included albas in that experiment. It either helped or didn’t matter. Warm stratification before cold didn’t hurt from my memory. In general now I take seeds out of hips soon after being ripe and then leave them sit in baggies of moist peat at room temperature until mid to late November when they go into the cooler. This process is nice too to delay germination for me a bit as we have a long winter and I don’t have too much space for seedlings to get too large on the plantstand before they can go outside.
When I did a lot of caninas, I used our natural winter here, which hovers between 33-40F, is dark, and very wet. So an outdoor temperate rainforest winter will do the trick. Only 1-2 days per winter will there be light snow, and about 1-2 weeks total have frost w/no moisture in the air. This also seems to work very well for rugosa and multiflora, but not so much for moderns, with some exceptions (like Shockwave, Summer Wind, and some other caninae descendents).
Good practical paper, easy to follow recipe for testing.
Suggesting change a few things for sortta related alba - key one, not letting seeds dry out as they have for last few days, and change to horticultural vermiculite for reasons given (already had) and warm then cold at near freezing for two months each.
This alba does “well” in my garden for winter (only 40% to 60% cane loss). Missed avoid mushy hip as a snap prolonged freeze in October.
Works for R.Rubiginosa here, seedlings completely cover the area planted in by spring. Winter here reaches freezing for maybe 12 hours total over the whole season…so even less cold than you. Agree with rugosa and multiflora germination doing well in the same conditions. Also agree with moderns being iffy with some more than others, most germinate at least somewhat though (but likely could be better), others germinate easily (Blue For You, Man of Steel, Many Happy Returns, Madame Annisette [she’s just iffy on setting seed, the seed she does set though is easy], etc).
None of this is on alba’s though, would assume it applies though as Rosa canina is a weed in Australia in the same range that R. Rubiginosa is including not particularly populated area’s (so spread by birds)