Is Rosa laxa a hybrid?

I have not seen R. laxa and know little of its variability. I pass along the following for its possible interest.

Peter Harris sent me a copy of Täckholm’s “Zytologische Studien über die Gattung Rosa” (Acta Horti Bergiani, Bd 7. no. 3, 1922).

Täckholm relied on Almquist to determine the identity of the specimens he examined for chromosome numbers. Under Rosa laxa he wrote, “Nach Almquist ist dieses Spezimen und überhaupt die ganze Art laxa als die Hybride beggeriana X cinnamomea anzusehen.”

“According to Almquist this specimen and indeed the whole type laxa is to be regarded as the hybrids beggeriana X cinnamomea.”

Täckholm went on to note that one specimen he examined was a tetraploid.

Almquist also regarded some varieties of R. beggeriana to be similar hybrids, or their derivatives.

In the entry for R. beggeriana Schrenk var. typica Christ, Täckholm explained that Almquist thought the leaves of the real R. beggeriana should be “clearly pointed”. The lack of this essential character (in Almquist’s opinion) indicated that such specimens were derived from crosses between beggeriana and cinnamomea.

Peter Harris sent me another paper dealing with the relationship between Rosa beggeriana and R. laxa. The authors found that the karyotype of R. laxa showed greater chromosome diversity than that of R. beggeriana. This fact, and the deciduous sepals of R. laxa, suggest that R. laxa is not an autotetraploid of R. beggeriana. The authors did not examine the karyotypes of R. cinnamomea and the related R. davurica, which might or might not provide further information on the origin of R. laxa, as implied by Almquist’s observations.

Karyotype and Flow Cytometry Analysis of the Natural Populations of Rosa beggeriana and Rosa laxa in Xinjiang, China
S. Yang, Y.J. Han, S.H. Yang and H. Ge
Institute of Vegetables and Flowers
Chinese Academy of Agricultural Sciences
Beijing 100081, China
As the typical local rose species in Xinjiang, R. beggeriana and R. laxa are highly similar in the morphology except that the sepals are deciduous in R. beggeriana while they are persistent in R. laxa after hips ripening. Both species had been applied to interspecific hybridization with modern rose cultivars for the introgressions of stress-resistances. In this study, R. beggeriana from three populations and R. laxa from four populations varied with different altitudes had been selected for ploidy and karyotype analysis. The results showed that the populations of R. beggeriana and R. laxa are diploid and tetraploid respectively. The karyotypes of seven populations of two species are all identified as the small chromosomes types, which belong to original, symmetric and ‘2A’ types. Moreover, different karyotype diversity was found in the populations between R. beggeriana and R. laxa.

Cutler, Hugh C. (1946). Races of maize in South America. Harvard Univ., Bot. Mus. Leafl. 12:257-291.
“It must be recognized further that a collection of plants is rarely a random sample of the population. Botanists have more or less innocently practiced misrepresentation for many years by selecting specimens of a convenient size or those which were the most attractive, the most nearly perfect or the most unusual, even when these were unique in the population they were supposed to represent. Thus, in the case of maize, colored or freak ears frequently receive more attention than normal ones. For example, in a harvest of 8000 ears at Santiago de Chiquitos, Bolivia, only four ears differed from the predominating type, yet in a collection representing this lot three of the atypical ears were included and only four of the major type.”

Though this statement refers to maize, the problem is the same with other plants. It is just too tempting to collect rarities because they stand out from the majority. But then someone who is studying herbarium specimens may suppose that the odd specimens are typical of something.

On May 30, 2013 I left Oklahoma City and reached to Damasca, VA on June 1. It was the height of the R. multiflora blooming season. This naturalized species was mostly uniform, but there were rare specimens along the way that had pale but definitely pink flowers. If I had collected specimens along the way, no doubt these pink-flowered specimens would have been over-represented.

When you come down to it modern roses originated with just four species of which maybe there were as many as five or six individual chinensis, a couple of individual moschata, a couple of individual multiflora and a single foetida.

If I had collected specimens along the way, no doubt these pink-flowered specimens would have been over-represented.

Probably just as well you didn’t. Depending on how you went you might have risked a year in jail.


No worries. I’m not making mass collections. And if I were, I would not be stopping along the interstate to take specimens. The two variations that I find mildly interesting are easily accessible. There is a pink-flowered Multiflora just a mile or so from my home, and the one I found with cupped flowers is further away, but safe from traffic and out of sight of the Multiflora police.

My particular concern at the moment, is how some botanists define species - and distinguish allied species - with far too few specimens. And to make things worse, they sometimes ignore specimens that conflict with their pronouncements.

Boulenger (1937) wrote about the remarkable resemblance of Rosa blanda to R. cinnamomea.

“According Crépin, the paired prickles are absent in R. blanda and this statement has been repeated in the synopsis recently provided by Ms. Erlanson, without referring to the var. geminata Schuette, which she had spoken of in a previous work (1925) on the Michigan Roses. But the experience I have gained of the genus Rosa made me doubt the absolute constancy of this nature and, as I expected, it did not take me long to find exceptions — I even identified seven cases among specimens determined as R. blanda by Crépin himself. While these are exceptions, yet we must not forget that R. cinnamomea, the type of Cinnamomeae of Crépin, with “prickles usually regularly paired” can show exceptions in reverse, both in Europe and in Asia; such exceptions, on both sides, are likely to embarrass anyone seeking to identify isolated specimens whose origin is unknown, so we should not ignore them.”

Actually, Erlanson cited var subgeminata Schuette.

In the same work Boulenger also wrote, “In a work that precedes this, I expressed the opinion that it is hardly possible to separate the R. gymnocarpa of America from R. Fargesiana of North China; if the specific distinction must be even, due to the imperfection of our knowledge of it, it remains questionable.”

Now it makes a little more sense to me how Almquist (in Täckholm, 1922) could regard R. willmottiae as a form of the American R. gymnocarpa, and R. davurica Pall. var lancifolia C. A. Meyer as R. blanda. R. davurica is closely allied to R. cinnamomea, which is confusingly similar to R. blanda.

The specimens Almquist identified as R. laxa (and, in his opinion, hybrids of beggeriana and cinnamomea) were diploids, with one exceptional tetraploid. Yang, et al. (2014) found only tetraploids in four populations of R. laxa.

There has been discussion and research into the proper identity of the plants grown in the U.S. and Canada as R. laxa and ‘Ross Rambler’. If they are diploid, they might be hybrids of laxa and cinnamomea, or derivatives from such hybrids.

Buck (1960) found that “Laxa-ness” (so to speak) was inherited as a unit character.

“Pollen from the ‘Crimson Glory’-R. laxa seedling was effective in producing viable seed on a wide range of cultivars of the Hybrid Tea, Floribunda, and Grandiflora garden classes. The seedlings segregate into two sharply defined groups of approximately equal numbers. One group bears a pronounced resemblance to R. laxa in growth habit, foliage and prickle characteristics. The flowers, which are borne only in June, are single, two to three inches in diameter, and are in the lighter tones of pink, salmon, and yellow. All the plants in this group are as hardy as the species parent. The plants of the second group resemble the garden rose parent in floral and foliage characteristics. The plants are June-blooming; the everblooming habit of the Hybrid Tea and the remontance of R. laxa being absent. All plants of this group winter-killed during the winter of 1958-59, even though they had been given winter protection. All the seedlings retained the freedom from powdery mildew and the susceptibility to blackspot of the ‘Crimson Glory’-R. laxa parent.”

Buck noted that R. laxa Retz. is allied to R. cinnamomea. It is not clear to me whether Laxa-ness should be regarded as Beggeriana-ness or Cinnamomea-ness.


A little background on hybrids and amphidiploids.

Judge Logan raised a seedling from the Aughinbaugh dewberry that was apparently a hybrid of that (pistillate) variety with a red raspberry growing near it. Logan was hoping for dewberry x blackberry hybrids (which he also raised), and was not aware that dewberry x raspberry hybrids were even possible. Despite the fact that his Loganberry was clearly neither a dewberry nor a raspberry, some critics refused to believe that an F1 hybrid could breed true to type. We know better, now.

I see that I didn’t finish what I had intended to point out.

The ‘Loganberry’ was a first generation hybrid of a dewberry x red raspberry cross. Burbank’s ‘Primus’ berry was also 1st generation, this from the dewberry and a Siberian raspberry.

Burbank’s ‘Phenomenal’ berry, to the contrary, was 2nd generation. Nothing so striking turned up in the F1.

Finally, Burbank’s ‘Paradox’ turned up in the 4th generation from a cross of Shaffer’s Colossal raspberry and the Crystal White blackberry.

The point I wanted to make is that if the tetraploid Rosa laxa is a hybrid of the diploid species R. beggeriana and R. cinnamomea (or the allied R. davurica), the chromosome doubling may turn up in the F1, F2 or later generation. This could account for much variation in R. laxa. And just as importantly, it could explain diversity in the diploid species, as the diploid hybrids revert (more or less) to the parental types.

It does strike me as odd that botanists can be so concerned with leaf details while ignoring the presence/absence of rhizomes. Hurst diagnosed R. beggeriana as DD, which implies that the specimen(s) he examined had rhizomes. R. cabulica, which Hurst noted was often labeled as R. beggeriana in gardens, was designated BB (with no rhizomes).

Lumping specimens based on leaf characters, while ignoring rhizomes, seems odd to me. Just as silly, I think, as designating various specimens in a segregating progeny as distinct species.

I think that with regard to the definition of species, we have to give a little slack to anyone born before 1900 or so. Earlier, there was a huge “splitting” tendency so that the number of so-called rose species was in the many hundreds. The concepts of hybrid sterility and self-incompatibility were not always well understood, so any time two roses failed to make seeds in a cross, it was perhaps assumed they were different species. Consider Austrian Copper or Persian Yellow. Are these species or hybrids? I for sure don’t know. Where would they survive and propagate if left to their own devices? Yet, who has succeeded in identifying parental species if they arose by hybridization? If you only had tools to look at visible phenotypes, you would tend to latch onto those. If you didn’t get roots with the specimen you examined, you could easily miss the presence/absence of rhizomes, or suckering roots, or root-produced adventitious shoots.

Herbarium specimens are often the result of opportunism- someone was passing through on a train or wagon and collected what they could reach in the time available. Very few botanists are so dedicated to a single family that they systematically collect it all over the place and do a full monograph on the variation within or between species. I know that’s the case at the K-State herbarium where my wife worked for a decade or more. Also, if you look at where some plant pathogen was first seen, you’ll see it was where there was someone looking. Distribution maps often track the presence of land-grant colleges, or large towns. This all leads to huge bias in sampling.

Is Johnsongrass or giant miscanthus a unique species, or just a cross of two well-known species?

Now that we have good cytology tools and can do FISH (fluorescent in situ hybridization) we can map out the chromosomes that contributed in these grasses, as has been done with common wheat and its progenitors. Until those tools came along it was not easy to sort out species.

Also, if we recognize that evolution is reticulate, not simply linear branching, we’ll find that there are quite a few zigs and zags on the way up the tree like the way strangler figs are woven into a self-grafting trunk. So we find sometimes there are plants that are unique recombinants of two species but won’t readily cross back to either of the parents, suggesting they are new species.

I don’t disagree about giving some slack to the pre-1900 crowd. However, there was quite a lot of lumping going on, along with the splitting. Boitard lumped roses into just three species!

And the issue of cross-sterility has always been confusing. For instance, Rev. William Herbert separated Sprekelia from Hippeastrum (both considered Amaryllis by Linnaeus) because he could not persuade them to cross-breed. But in a different place he mentioned that he could not persuade Sprekelia to set seed from any pollen, even its own. Other experimenters have successfully crossed Sprekelia and Hippeastrum, raising fertile offspring, yet few people today would reunite them in a single genus.

Heslop-Harrison (1921) quoted Linnaeus as to the difficulty of delimiting Rosa species, then continued:

Although written more than a hundred and fifty years ago, to most botanists, even of to-day, the above extracts from the > Species Plantarum > appear to be as true as Linnaeus imagined; as a natural consequence, except to the specialist, the genus Rosa is more or less of a tabooed subject.

Nor can this be wondered at when the novice beholds the bewildering array of forms, seemingly alike, masquerading under different names in the carefully labelled herbaria of the rhodologist, or even after he has attempted to name a casually collected rose by means of some flora. Both experiences are disheartening, but to the enquiring mind readily understandable. In the first place, so casually are rose specimens accumulated, and so effectually does the process of drying repress any but the most unreliable of characters, that forms, in reality most diverse, in the end look precisely alike; for example, it is quite an easy matter to produce a form of > Rosa coriifolia > so similar as a herbarium specimen to a member of the > tomentosa > group that even to the trained eye they are almost indistinguishable. If then the original descriptions of species be based on such material, as they often enough were, how little can we expect such accounts to square with the roses as they grow in nature, and how futile, therefore, our endeavours to determine a plant by their aid. Even with an ordinary genus a dried specimen may prove troublesome enough although the obstacles to a correct determination are not insurmountable, and so would it be with > Rosa > were it not that its members—call them species, little species, elementary species, microgenes or what you will—are so excessively variable that another difficulty arises. In some cases no two bushes are exactly alike; by that very fact they practically invite the attention of some individual blessed (?) with the “mihi”—or what Crepin used to call the “bush-mania”— who forthwith sees material for a possible new species. Obviously enough, the most hardened sinner would avoid the error of describing, as distinct, plants differing merely in some microscopic denticle on the back of the main leaf-serrations or in characters of similar value. Far from it, he selects his specimens from a bush as remote from the nearest book description as possible and upon those erects his “new” species.

Trans. Nat. Hist. Soc. Northumberland and Durham 5(2): 244-325. (1921)
The Genus Rosa, its Hybridology and other Genetical Problems
J W Heslop Harrison D.SC

The fact that two species that are clearly distinct while alive can appear indistinguishable when pressed and dried is of great concern to anyone making a serious study. And I am just as concerned that so many collectors take only branches, ignoring roots and rhizomes that should be of more interest than minor differences in the leaves.

I don’t know about Johnson grass, aside from the fact that it hybridizes with Milo. The grasses do make for interesting studies. Sugarcane, for example, has been hybridized with both sorghum and maize. And partial hybrids of Rye x Maize have been stabilized with all 42 Rye chromosomes and a single pair from the Maize parent.

The discovery that hexaploid bread wheat is derived from a single species of Triticum and two species of Aegilops came as a bit of a surprise to some systematists. And the fact that the three sets of chromosomes remain recognizably those of the three ancestral species (with some modifications) is worth noting in regards to Hurst’s “septet scheme” – even though it is merely coincidental that wheat and its kin have chromosome numbers that are multiples of 7 (as in Rosa).

Evolution is not always reticulate, though. Sometimes when species hybridize, some of the possible segregates are not found because of environmental constraints. The Louisiana irises Iris hexagona var giganti-caerulea (HGC) and I. fulva occasionally hybridize despite the fact that the former is visited by night-flying moths, while the latter is pollinated by butterflies. The species also differ in their tolerance of “wet feet”. And so, the surviving hybrids usually tend strongly to favor one or the other parent. However, where the environment has been disrupted by digging channels between bayous, for example, hybrid swarms may appear in all their reticulate glory thanks to the “hybridization of the environment”.

As for Rosa foetida, I have to wonder whether anyone has tried growing it dry in the summer and let it go dormant, rather than trying to keep it growing by watering. Collins (1905) reported that both the Mango and the Avocado may thrive in regions with continuous high humidity, but refuse to fruit. Both require a dry season to be fully fertile. Perhaps this is also true of R. foetida.

Thank you Karl for finding those refs. About R foetida you’ve a very interesting idea, but I think that parts of Colorado would meet the requirement of dry summers. Yet, I’ve never heard of hips there, or anywhere. I got one hip out of a hundred or more pollinations with Carefree Beauty, one year. That’s it. I forget what else I tried on it.

Do the mangos fail to bloom, or act sterile? With R foetida there’s no bloom failure. What about things like minutifolia and R persica (Hulthemia) I wonder.

I got one hip out of a hundred or more pollinations with Carefree Beauty, one year.

I’m whittling on seeds now that are f2 to that cross. Not a lot of embryos but some, with moyesii and woodsii fenderli pollen. There is a single seed from CC pollen on 54-08-01 but I haven’t gotten to it yet.

I think genes are as important as environment with foetida fertility. Harison’s Yellow set hips two years running since having been planted out in a bed of other spins and right next to Dorenbos Selection. It might be useful to make some planned crosses in that direction with foetida proper.

Piecing together statements from various authors, I suspect that R. foetida is a highland plant that relies on water stored deep in the soil, rather than from rain during the growing season. It also seems that the short-lived foliage is an adaptation to a short (3=4 month) growing season. As the hips ripen (in the native area) the leaves drop and the bush goes into its summer dormancy. Does it remain dormant until the following Spring? I’m guessing that it does, though the plants may start to grow again in gardens, particularly when grafted to roots of other roses.

Apparently R. foetida can set seed, sometimes.

“This interesting variety [Williams’ Yellow] was raised about ten years ago by Mr. John Williams of Pitmaston, near Worcester, from seeds obtained from the single yellow rose, which but very rarely matures its fruit in this country. Among the seedlings raised on that occasion three proved to be double, one of which is the subject before us, which from its flowering freely, and from the size, form, and colour of its blossoms is justly esteemed a most valuable addition to our collection of hardy roses. Mr. Williams, in a communication to Mr. Sabine, describes it as a plant of vigorous growth, and that it sends forth abundance of suckers.”—D. Don in The British Flower Garden, v. 4, t. 353 (1838)

Williams had previously (1824) mentioned that the Double Yellow Rose [R. hemisphaerica] bloomed fairly well when budded to the Musk Cluster Rose. I don’t know whether the seed parent of his Double Yellow was budded or own-root.

Also, John Gerard (1597) wrote, “the seedes of yellow Roses have brought foorth yellow Roses, such as the flower was from whence they were taken; which they woulde not do by any coniecturall reason, if that of themselves they were not a naturall kinde of Rose.”

As for mangos and avocados, Collins stated only that they did not bear fruit, or were not so prolific, when raised in constant humidity.

The Avocado, a Salad Fruit from the Tropics USDA B.P.I. Bull. 77. p. 31-32 (1905)
G N Collins
Extension of season is an important desideratum, especially in the direction of later fruiting forms, the desirability of which is considered farther on. Advance in this direction is likely to be made by the introduction of new varieties and, perhaps, by extending the cultivation of the trees to regions of more continuous moisture where the season of flowering can be to some extent controlled. The tree flourishes in many localities where it fails to bear fruit, and, as with the mango, this sterility is usually found in localities of almost continuous humidity. Under such conditions an artificial check, such as root pruning, has been found to induce flowering and the setting of fruit. This can easily be overdone, however, in which case the trees will bear one large crop and then die.
Some of the most prolific trees are those grown in rather small depressions of porous rock in southern Florida, where the plants are, in a manner, root-bound, while the porous nature of the rock affords good drainage. There are a number of ways in which the growth may be checked and the yield increased. The baring of the roots to the sun would appear a very satisfactory method. A custom of hacking the trees to make them bear is practiced by the Indians of Mexico. In any case where the fruiting is induced by artificial means the season will be more or less under control.

The Mango in Porto Rico, USDA B.P.I Bull. 28. (1903)
G N Collins
The mango will grow in a variety of conditions, and it seems to have little preference as to soil, the most important requirement being a deep soil that is well drained. As to climate, it is much more exacting, and the fact that the tree may thrive in a given locality and yet fail to produce fruit should always be kept in mind. It may be considered as proven that the mango will be prolific only in regions subjected to a considerable dry season. On the moist north side of Porto Rico the trees grow luxuriantly, but they are not nearly so prolific nor is the fruit of such good quality as on the dry south side, and in the very dry region about Yauco and at Cabo Rojo the fruit seemed at its best, while its abundance was attested by the fact that fine fruit was selling as low as 12 for a cent. In Guatemala and Mexico the mango was found at its best only in regions where severe dry seasons prevailed.

Interesting thread having acquired young laxas (maybe both a diploid and tretraploid based on a verbal map).

And due to a appreciated transfer from a dedicated pure hardy hybridizer, my rose prize of the year - maybe new decade - “Rosa beggeriana nigrescens’ - (source origin back two owners to Loubert).

Or alternative name, I like describing it as a single pink flowered, “Black” R. beggeriana nigrescensa - coined by an Albertan rosarian from a provided French translation as to meaning. Hips have been confirmed as black coloured with pic proof as Polstjarnaan has been tough over the various tries.

Look forwarded working synergistically with these two rose varieties to get a tall “climber/ rambler” with moderns. Years down the road.

Photo credit “Andre” from “Quebec”