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THANK YOU for posting this, it's a huge help for people in hot climates!!!!
Do you have any other Austins that are as heat resistant?
Nate
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Thanks for your comments raingreen.
Many Austin roses do well in hot climate if given a location with dappled shade less CPM which is performing well even in full sun. The bloom size, however, reduces and so does fragrance. Those that have done well with me (with reduced bloom size plus reduced fragrance) include St Swithun, The Prince, Jubilee Celebration, Princess Alexandra of Kent, Pat Austin, The Dark Lady, Graham Thomas, William Morris, Lady Emma Hamilton, The Alnwick Rose and Huntington Rose. I have given a two inch top layer of home made compost to my roses (most of them are in pots) that is rich in K, Ca and trace elements. Ca enhances ability of roses to fight heat (in my view) though it does lighten the shade of blooms.
Moreover, root stock also matters in case of grafted / budded roses. My Austin roses grafted on centifolia rootstock have performed far better in heat than those grafted on multiflora / Dr Huey rootstocks.
best regards
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Yes, I managed a container garden and found Calcium deficiency to be a problem with the plants I was giving 'high bloom' fertilizer (high in Phosphorus). If I could do a container garden again, I would not use a high-P fertilizer but use P in a more equal ratio w/ higher K for disease and drought resistance and maybe use supplemental Calcium as well:-).
Again, thankyou for your observations. I'm using Crown Princess Margareta in a garden because of your observation on heat tolerance. It's interesting that you found Pat Austin to be heat tolerant, sometimes it is considered heat sensitive.
Nate
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Khalid is right about his roses on Centifolia rootstock as being more drought tolerant. I have a Centifolia rose and never water it. But Pat Austin as own-root is wimpy and a water-hog, despite in less than 4 hours of sun. Grafted on an aggressive rootstock like Centifolia helps with drought .. my Centifolia rose sends suckers through my rock-hard clay, and I don't even water it.
Heat-resistance has to do with the thickness of petals and the thickness of leaves. Roses that last long in the vase have thicker petals that don't fry in hot-full-sun. Crown Princess Magareta CPM is my favorite cut flower for the vase, and its leaves is quite thick. Old Garden roses like Comte de Chambord, Duchess de Rohan are NOT heat-resistant, their petals are so soft that they fry easily in full sun, these last 2 days in the vase ... compare to CPM which lasts 4 days in the vase.
The best combo would be heat-resistant roses (thick petals and thick leaves) grafted on a drought-resistance root-stock like Centifolia. Dr. Huey-rootstock is good for heavy clay, but it doesn't spread out widely like Centifolia. Multiflora-rootstock is the worst for dry and hot climate .. that one prefers acidic loamy soil with tons of rain.
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Thanks Straw. In addition to petal substance, heat-shock proteins probably also underlie heat resistance in roses---see http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2009.01987.x/full , article on heat shock proteins in roses. They are special proteins that protect tissue from damage under high temps....according to the article the same proteins also protect against other stresses like cold. Altho the rose people at Gardenweb don't appear to be aware of the proteins, they may be the reason heat-tolerant flowers tend to last as cut flowers. The proteins protect against the oxidation reactions that occur in decomposition, so flowers stay fresh longer.
Thanks!
Nate
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Thanks Nate, for a fantastic biochemistry explanation of heat-resistance.
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raingreen, thanks for info on hardshock proteins. There is so much to learn about roses.
best regards
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Interesting paper. Thanks for the link. It reminded me of some of the things said in the Tea rose book (Chapman et al). Some of the ones that last exceptionally well when cut are also ones that are exceptionally good in summer. Heat shock proteins sound like an obvious contributing factor here, although probably wouldn't be the only relevant factor.
These lines were interesting too: "However, the growth of most R. chinensis varieties is limited by unfavorable environmental conditions such as high temperature, high salt concentration and drought. Under stress conditions, these varieties do not blossom but enter dormancy directly..."
Which is what established Teas do. The book says if there's a drought on you just stop feeding them and they'll sit in dormancy quite happily. Then when it rains again you just feed them again, and off they go.
I wonder if there's any research on HSP's in R. gigantea.
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Note, they were being imprecise...they're calling a floribunda, Schloss Mannheim, R. chinensis. SM is actually a son of Europeana which also shows unusual tolerances, thriving in both Texas heat and subarctic conditions in Scandanavia.
I actually want to know about HSP in R. chinensis itself, and R. gigantea. Guessing, based on the distribution, that R. chinensis would have more HSP than higher-elevation R. gigantea. Gigantea hybrids and the primitive tea Safrano don't do well for Robert Rippetoe in Palm Desert, California, being prone to sunburn. And he likes Chinas: "In my opinion Chinas are the ultimate drought resistant rose suitable to modern gardens. (private HMF message from Robert Rippetoe)"
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I missed that they were using Schloss Mannheim, Good point about imprecision. It'd have some chinensis genes in it (probably couldn't find a modern rose without them), but it's far from being straight chinensis.
Alister Clark had good results using gigantea as a parent for roses grown in hot conditions, so it can't be too bad. Also its natural range (northeast India, northern Myanmar, and Yunnan in China) appears to get similar temperatures to the natural range of chinensis (Guizhou, Hubei, and Sichuan).
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#11 of 19 posted
20 JUN 16 by
 raingreen
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Here is some data on climates of the 2 species. R. gigantea does appear to inhabit cool-summer climates. The Alister Clark giganteas do well in my area (Pomona, California) which is somewhat like the climate in south Australia, with occasional extreme heat. However, Robert Rippetoe is the last word on heat tolerance (Palm Desert, California).
I've been wondering about the climate characteristics of R. gigantea for a long time, and I've tried before to find representative climates (unsuccessfully). I don't mean to quibble, just trying to get closer to understanding the plants. My understanding is that the cultivated teas and chinas are intermixed hybrids of the 2 species.
R. gigantea "Mixed forests, thickets, scrub on hillsides, pastures, grassy slopes, roadsides; 1400--2700 m. Native in Yunnan [Myanmar, N Thailand, N Vietnam]. (Flora of China online)"
July low/hi for representative climates:
Sa Pa, Vietnam at 1500 m 64/74 F 18/23 C
Kunming, China at 1900 m 62/75 F 17/24 C.
R. chinensis spontanea "Rocky slopes and hills, usually on limestone and shales, 500–
1950 m. Sichuan, Gansu, Hubei, Guizhou. (http://www.theheritagerosesgroup.org/articles/rchinensis-spontanea-rix.pdf)"
July low/hi for representative climates:
Guiyang, China at 1300 m 69/83 F 21/28 C
Zunyi, China at 860 m 71/86 F 21/30 C
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I just took a quick look on Wiki last night for climate ranges. Really we're only talking a few degrees difference between 24 and 28. Even 30 C isn't that hot. But yes, throwing the poor things into an oven in the California desert would be a whole 'nother game. The thing about subtropical climates is that when it's hot there's usually some humidity around too. Not the case in the desert, so I can see that really hammering subtropical plants. And highs of up to 49 C is really cooking.
"My understanding is that the cultivated teas and chinas are intermixed hybrids of the 2 species."
Teas definitely are. Some of the things we call Chinas definitely are. Not so sure about others. As far as I understand it the older "Chinas" like Old Blush and the other "stud Chinas" are probably just chinensis hybrids. Other "Chinas", like Comtesse du Cayla for example, have Tea mixed into them which would mean some gigantea genes in there somewhere.
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Oh and I spotted this when looking around: "According to rose historian Brent Dickerson, the Tea classification owes as much to marketing as to botany; 19th-century nurserymen would label their Asian-based cultivars as "Teas" if they possessed the desirable Tea flower form, and "Chinas" if they did not."
From https://en.wikipedia.org/wiki/Garden_roses#Tea
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#14 of 19 posted
21 JUN 16 by
raingreen
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Thanks Give me caffeine. I'm trying to find roses that are highly drought resistant for my area so I'm looking for insane, rather than reasonable, levels of heat tolerance. That is because I believe heat effects increase in dry soil.
There was a study on the Mediterranean island of Ibiza by Mattocks roses that found that the Teas died off when they were left dry during the summer drought--I had been pinning my hopes on the ability of the Teas to go dormant in summer heat, but apparently they can only tolerate moderately harsh conditions. That was a big disappointment, because Tea roses should rule :-).
Robert Rippetoe did say Mrs. B. R. Cant was a star performer in his conditions.
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It might be worth trying General Gallieni too. That has a reputation for good performance in hot weather.
Another bunch worth looking at could be the Bishop's Lodge roses that were found surviving at Hay, NSW. They're in the garden listing here under the Bishop's Lodge name. I think some of them are available in the US. Anyway La Roseraie du Désert claims to ship world wide if you're keen.
Hay has a pretty extreme climate: https://en.wikipedia.org/wiki/Hay%2C_New_South_Wales#Climate
What Khalid said about centifolia rootstock is probably worth trying too. It'd be interesting to get budwood for a few Teas and try them side by side on different rootstocks.
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Quite a few of the Bishop's Lodge roses are on R indica major (Fun Jwan Lo) rootstock, which is a survivor in dry areas (often more so than the scion it used to carry).
I'd go for Teas (and Chinas and Noisettes and Polyanthas) on their own roots any time.
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I intend to try some on their own roots at my place, but have bought some on rootstock just to get started. AFAIK nobody sells own-root plants in Australia.
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Oh and I just spotted this member's stuff. The conditions there sound analogous to yours.
http://www.helpmefind.com/gardening/l.php?l=3.24680
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#17 of 19 posted
22 JUN 16 by
raingreen
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Thanks for the tips Caffeine
I'm looking for the winter growth and I'm assuming the centifolia stock wouldn't work for that?
My dream is to cross the hardy David Austins like Crown Princess Margareta w/ Rosa minutifolia. Of course R. minutifolia needs no water at all in my climate. Yes I have rose ideas all over the place.
Nate
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