In my opinion, the two most desirable colours to develop in a breeding program are purple and yellow. The reason for this is obvious. Since these two colours are more uncommon in roses, the novelty of them is attractive to the gardener or rosarian. This is especially true in cold climates, where Floribundas and Hybrid Teas having purple flowers are difficult to grow and never size up like they do in warmer climates.
In cold climates (Zone 3), there are several hardy yellow cultivars that can be successfully grown. For example, ‘Agnes’, ‘Harison’s Yellow’, ‘Hazeldean’, ‘Persian Yellow’, ‘Morden Sunrise’ and ‘Topaz Yellow’. The latter two cultivars winter kill severely but bloom on new wood. However, hardy purple cultivars are rare. The only hardy purple cultivar is Robert Erskine’s ‘Caroyal’ (‘Hansa’ x ‘Lac la Nonne’). The breeding of ‘Caroyal’ gives us one strategy to develop hardy purple cultivars. That is, a back cross to provide a double dose of the purple red colour that ‘Hansa’ has. In fact, I call this method 'double dosing" to develop a desirable flower colour or shrub characteristic. I think it’s possible this is the way the purple Rosa gallica cultivars were developed, but a different climate and no doubt other circumstances did not allow the development of purple Rugosas many years ago.
The second method to develop the purple colour in Rugosas is to use a species in the breeding program that develops it in the progeny. Again, we have a good example in ‘Basye’s Purple’ that has the species Rosa foliolosa in the parentage. In an attempt to duplicate ‘Basye’s Purple’ but having semi-double or double flowers, I crossed ‘Hansa’ with Rosa foliolosa. The result was progeny with semi-double, medium purple flowers. One selection was registered and named ‘Purple Springs’ in late 2005. It is hardy to Zone 2.
There is no reason, since we know how to do it, why the colour purple cannot be more common in Rugosas. All it takes is the effort and time to do it.
Congradulations Paul on your ‘Purple Springs’. I agree with you about colors and have tried to consciously breed for warm colors (yellows, oranges…) and also purples in hardier roses. One thing that people can do if they have the resources is to follow up on pH and flower color. THe purple in modern roses generally isn’t due to a different anthocyanin (color pigment) than in most pink and red roses, but pH and interactions with metal ions and other factors. A few years ago I did a petal pH survey (grind up a certain weight of petals and added distilled water and used the pH probe) of different colored roses and saw a clear trend for higher petal pH being associated with more purple coloration. It was especially interesting to see the change in petal pH at opening to senescence for those roses which “blue” with age (turn purple). I came across an article before this that looked at the cause of ‘bluing’ in ‘Mercedes’ cut roses and they attributed it mainly to pH spikes. This article gave me the idea to look at pH of some cultivars and seedlings and try to see how pH can be used to breed for particular color effects. I think that if we want purples we can choose parents which have a higher petal pH to help with the goal. For instance, Rise 'N Shine has a huge pH spike. So, if we want a rose like ‘Distant Drums’ that has some warm background colors (carotenoids) and then overlaying anthocyanins which first appear pink and then age to purple RNS may be a good parent to provide the carotenoids plus the potential for pH spiking to allow anthocyanins from another parent to go through the color transition. ‘Snow Pavement’ has a very unique soft mauve/purple. I wonder what can be obtained from using it as a parent with ‘Hansa’ or other more purple rugosas?
Your idea of looking at the pH of cultivar and seedling flowers for use in breeding programs to develop purple flowers is very exciting. Interestingly, Rosa foliolosa (‘Basye’s Purple’) I would expect grows in soils of a relatively high pH. Rosa acicularis, reputedly one of the parents of ‘Lac La Nonne’(‘Caroyal’), is often also found growing in soils of a high pH.
In October I was botanizing the native roses in an area of the centre part of the Alberta/Saskatchewan border. The soils in this area are generally poor in quality and have a high pH. I was surprised to discover that the most common native rose is Rosa arkansana. My intention is to go back to this area next July to see what variation there is in the flower pattern/colour of the genotypes (Rosa arkansana has much more variation in flower pattern/colour than the other two prairie native species, Rosa acicularis and Rosa woodsii). I should do the pH test to see if there is a correlation between it and flower patterns/colours.
I got full flowered plants similar to ‘Basye’s Purple’ a few years ago but all darker seedlings were with the poor growth habit of this var. I do not like these black-red stiff stems and sparser dark foliage here french Riviera.
Do your ‘Purple Springs’ have a better plant habit?
F1 foliolosa hybrids are pretty well higher PH soils tolerant but the further generations are often as chlorotic as the succeptible parent.
Are your hardiness requirements not met by the multifloras? I suppose most of them are more zone 4 than 3, but the numerous rambling multifloras (Rose marie Viaud, Amethyste, Vielchenblau) as well as smaller mulitfloras (Baby Faurax) would suggest great potential in this class.
David, do you know if the pH of the multifloras supports your theories concerning hybridizing for pH?
It is my impression, though perhaps wrong, that “purpling” in roses, much like low-centered “cabbage” forms, was considered to be an undesirable trait for some time, and roses with such attributes were culled from breeding stock. I would agree that it’s almost surprising that there aren’t more roses with this color.
I’m curious though, are roses with clearer yellows likely to have higher pH’s? Breeding with clear yellows was advised to me for achieving “bluer” mauves. I always assumed it was because a clearer yellow would lack a pigment which might otherwise “muddy” or warm up a purple hue. (I wondered why a white wouldn’t suffice as it would seemingly lack a “muddying pigment.” But some white roses, it is my understanding, are not white for want of pigments so much as they lack the ability to finish developing the pigment precursors (having no enzyme dihydroflavinol reductase) to a visible colored chemical. Depending on whether an offspring acquires the DFR gene or not, a white rose may have white offspring, or some other color hidden in its ancestry. But I digress, and you guys probably already know more about that than I ever will…)
At any rate, multiple biogenetic firms are working to introduce delphinidin genes to roses, (florigene, for instance, who created “blue” carnations in the moon series through recombinant gene work) though they too have the pH obstacle. Apparently, they introduce numerous genes into a selected cultivar including a knockout for the rose DFR (to clear the color) a delphinidin gene from a petunia, and a new DFR gene from an iris to finish the petunia delphinidin so that it is visible. I don’t know that the color is much better than say a “blue girl” since rose pH is lower than carnation.
i will refrain from commenting on such techniques…
My ‘Purple Springs’ has a better shrub form than ‘Basye’s Purple’. It is stockier and more upright but also much more thornier. The development of this cultivar clearly indicates how the direction of the cross, when doing species or near species hybridization, can highly influence the form, texture and hardiness of the shrub and to some degree the appearance of the flowers. This fact should always be kept in mind when breeding at the species or near species level.
Philip,
Good point about the possibility that seedlings with purple flowers could have been discarded from early breeding programs.
You also make a good point about using the Rosa multiflora rambling cultivars with purple flowers in breeding programs. However, these cultivars are, of course, not cold hardy in my Zone 3 climate. I would also be leery of using them in a breeding program because of their susceptibility to powdery mildew. Having said that, I think an optimum breeding program should incorporate Rosa multiflora to obtain floriferous and graceful shrubs. It’s always been one of my goals to cross Rosa multiflora with Rosa acicularis to obtain a relatively cold hardy tetraploid breeding line that can be used for further breeding. Hopefully, I’ll accomplish that this year.
I confess I have very little familiarity with the species roses, and even less experience cross-hybridizing them.
At any rate, given my geographic location I am more inclined to look to the yellow single Banksias for my goals! Purezza gives me some hope that a recurrent yellow might be possible.
Back to the topic however, I wonder if anyone has done more extensive comparisons of rose pH’s…
My friend asked that question. I had wondered about the Ph and the huge variance in color with Rosa californica since the pH in it’s habitat range is quite variable. Plus it seems to be rather tolerant (aka grows like a monster) of acidic soil here.
