I was going to reply to the “Perennial Blue” thread wherein Kim made a comment about susceptibility to chlorosis, but this is really changing the subject.
Chlorosis is an issue for me here in NW Minnesota, most notably with rugosas. Therese Bugnet is also susceptible to chlorosis here. Our soil is a pH of about 7.5 or higher.
I asked Margit Schowalter if she saw any rugosas that may have been less susceptible to chlorosis, and after taking a look she mentioned only White Pavement. Of course soil can vary like microclimate, so her observation of a single plant isn’t definitive.
It would valuable to develop a rugosa rose that was less susceptible to chlorosis.
I’m interested to hear observations about which roses might be particularly susceptible to chlorosis, or may pass on chlorotic tendencies. Also, from those people living in areas with alkaline soil, if any hardy roses showed a surprising tolerance to alkalinity.
With rugosas, it is very much a matter of soil pH. Anything over 6.0 I’ve heard they don’t like, although it might be up to 7 before they show symptoms. When the pH of the soil is high, the iron in the soil becomes unavailable to some plants. That’s when the turn yellow.
For what it’s worth, in my Rugosa-friendly soil I’ve seen seedlings vary in their tendency towards chlorosis. Most seedlings of a particular cross are fine, but one or two will stand out with their yellow leaves. That leads me to think that susceptibility to chlorosis may be more of a spectrum than an either-or proposition. It may be very much worthwhile to try developing Rugosas that tolerate alkaline soil.
I never tested mine, but from the calcium deposits everywhere, on everything and knowing everything from the ocean to Arizona is ancient sea floor, they must be pretty strong. The soil is very clay/hard pan, which resists absorbing water even when broken into small pieces. Once massaged by copious horse manure, regular moisture and a few months of real heat, it sucked up and held water like mad. In these conditions anything strongly multiflora, rugosa and anything really violet toned turned sickly, ghostly pale green with pastel, nearly white flowers. Reine des Violettes required an Ironite mulch with generous saturated peat moss be worked into the soil around its root zone, as did International Herald Tribune, Violet Hood (and the other purple Lens hybrid multifloras), Blue Mist, Mr. Bluebird and Baby Faurax. Ironically, Cardinal Hume never expressed any iron issues at all, even own root. He was so reliable, I still have a four bud standard I created using Hume as the trunk. If I recall correctly, the tag on it is dated 1994, so he’s a pretty durable stock.
Rugosa chlorosis is something I am working at with two sides.
The soil of my rose field is alcaline enough for most rugosa derived seedlings to exhibit at least when leafing out a transitory to permanent chlorosis.
First is breeding rugosas with less prone to chlorosis species. Mixed results here as chlorosis is not weeded out as hoped.
Second is using mycorrhizal fungi that is very promising even if my plantings weres last two years perturbated by quite unusual floods.
I have heavy clay soil that’s fairly alkaline so my Rugosas can get chlorosis pretty bad, but oddly it varies from year to year. I would say that my rugosa seedlings have gotten it worse than the varieties I grow. But if my memory serves me correctly (and that’s a big IF) I think Showy Pavement and Schneezwerg have gotten it the worst with Blanc Double de Coubert and Darts Dash getting it the least for me. My Therese Bugnet has had a lot of issues also and hasn’t put out much growth so I don’t know if chlorosis is among them.
Like you I would like to create a Rugosa that is more chlorosis resistant so I’ve crossed both Showy Pavement and Blanc Double de Coubert with R.blanda, because R.blanda is native here so it’s adapted to our soil. Also because the R.blanda I’m using is thornless.
If I may extend this a little, what species, species hybrids or classes of roses are least prone to chlorosis. (Presumably such might be used with rugosas to temper their sensitivity, no?) I’m in the south, so I’m not that concerned about cold-hardiness, but rather heat-tolerance, and my soil is clay and caliche (nasty stuff) so I’m anticipating issues.
I would have guessed that R. californica might have a tolerance, but as I believe she is in the pedigrees of some of the mauves mentioned as chlorotic…
What about R. woodsii or R. stellata? (Has either really been explored at all? I dunno why, but looking at photos of stellata, I remembered an old shrub of “Petite Pink Scotch” I saw somewhere in TX. I don’t think there is a relation…)
Though I’ve never really done anything to affect or test them, Californica, Hugonis, Stellata mirifica and Fedtschenkoana have never expressed chlorosis in either climate (mid desert and savannah) here. Roxburghii, however, is complaining bitterly right now about just this, or at least it LOOKS like chlorosis. I’ve also not seen the issue on any of the Fedtschenkoana seedlings. Purpurea, the- China, seems extremely resistant to it here. I’ve never witnessed anything resembling chlorosis on it, nor on Fortuniana. 86-3, the Basye Banksiae - Laevigata cross, is prone to it.
Putting Paul’s and Kim’s information together, it would seem crossing Dart’s Dash with Cardinal Hume or Purpurea would have a decent chance of creating a good mauve Rugosa for California and other alkaline areas. Does anyone have those varieties on hand for a test?
I have a root sucker from Hume under the Baby Faurax standard and I have Purpurea. Linda Campbell (totally sterile to date) is the closest thing I have to a Rugosa anymore. Rugosas simply HATE it here, so they’ve gone where they’re happier, making me even happier.
I have Purpurea and Therese Bugnet, so I can cross those in a few weeks. I can test the seedlings with some home made high pH water and soil.
This is interesting to me because it relates to my salt tolerance line, salt and alkalinity often go together. I need a few more Rugosas anyway, I think I’ll pick up a Dart’s Dash.
I hope you guys aren’t basing your decision to get Darts Dash because of what I said. What I said is based on the best of my recollection and that’s pretty iffy. I moved my Rugosas last spring to a better spot and there wasn’t much of a problem with chlorosis last year. It was in 2010 before I moved them that there was a problem with chlorosis and most of that was with some pure R.rugosa that I had grown from seed. I do remember that Darts Dash and Blanc Double de Coubert were healthier than Schneezwerg and Showy Pavement in 2010, but how much of that was from being less suceptable to chlorosis is hard to say. When I moved Darts Dash last spring I planted it too close to the other roses so it was over crowded and it suffered from BS more than the other Rugosas did.
David Mears asked: do you think the ‘mycorhizal fungi’ might inoculate the rugosas over time if grown in that sort of enritched soil ?
Is R, rubra effected there with this problem ?
Mycorhizal fungi act just as a very spectacular soil improvement. From the better roots mycorhize induce: in the seed tray and after transplanting growth is much bettered and chlorosis minimized. Soil will be inoculated, roses need reinoculation when severely barerooted.
Hans of Bierkreek as asked about how it is possible to manage a no chemical rose nursery pointed to mycorhizal fungi.
All rugosa and derived of progenies are more or less affected with individual variation. Selecting for chlorosis resistance rather ineffective.
Native here species sempervirens is chlorosis immune.
We shouldn’t write off Linda Campbell as a pollen parent. The pollen I examined was 25-40% fertile. Here are two pictures of seedlings from Linda Campbell pollen. The yellow one is with Pacific Serenade as the mother, and the white one has Everest Double Fragrance as the mother. Both are from the 2009 season. In the background of the EVDF seedling you can see some downy mildew on leaves. Yes, this was indoors, under the lights.
Don Holeman extracted the embryos for me–he was practicing for the Pro-Am Invitational Embryo Extraction Tournament. (He was seeded first, and took an easy win.)