Roots - the neglected part of breeding roses

The focus of rose breeding, of course, has been on the development of attractive flowers. In recent years, breeders have devoted more attention to developing disease resistant shrubs. There is now more emphasis on having shrubs with good architecture and attractive foliage. But very little attention is paid to root systems, despite the fact the increasing trend of marketing roses grown on their own roots.

Rose species, of course, have root systems adapted to the ecosystem they grow in. For example, Rosa arkansana has a deep root system, enabling it to grow in dry geographical regions having poor soils. Conversely, Rosa palustris is adapted to growing in wet soils. Rosa acicularis and Rosa rugosa grow in soils having poor nutrition. But the latter species is also susceptible to chlorosis, if the soil pH is to high or if it is too wet.

I’ll never forget having to discard some Rosa palustris shrubs, because they had suckered too much. The root systems of them were massive. So I wonder why a trait like this can’t be incorporated more in breeding programs. We know so little how a rose root system affects the shrub’s ability to take up nutrients, which likely is a major factor in the vigour of it. And I don’t think we know anythng about combining rose species in a breeding program that optimizes the development of root systems, which could be valuable, for example, for growing roses in containers or in geographial regions having extreme climates.

I would like to see a maor research program done on this subject, but there is no reason, of course, why amateur rose breeders can’t also do some work in this respect. Perhaps some breeders have already made some good observations in their work of using species in their programs. If so, I would like to hear about them.

Good point.

I think that selecting for “how it does” will automatically cull those with weak root systems, as long as one is trialing roses in the ground.

Selecting for root vigor (and type?) at a fairly early stage in seedling development might be a way to predict garden performance, if one is limited in garden evaluation space.

Random side thought… Several years ago I grew out some F2’s and F3’s of a cross between Dianthus amurensis and a random annual dianthus. I selected for silvery foliage, a neat mounded habit, and flowers that were deeper in color that those of D. amurensis, which is kind of lavender. Then I kind of forgot about the project, but had some plants scattered around in our gardens. For whatever reason, including getting overrun by weeds, they vanished one by one until this summer there were only two left. I decided that there must be some merit to the survivors, and chose to dig and divide the best looking one. I expected a fairly shallow and fibrous root system, and was amazed by the depth and thickness of the roots under the clump. In this case, perhaps the nature of this plant’s root system helped it to be a true perennial in this difficult climate.

"So I wonder why a trait like this can’t be incorporated more in breeding programs. We know so little how a rose root system affects the shrub’s ability to take up nutrients, which likely is a major factor in the vigour of it. And I don’t think we know anythng about combining rose species in a breeding program that optimizes the development of root systems, which could be valuable, for example, for growing roses in containers or in geographial regions having extreme climates. "

I really think that there is a lot of selecting and culling for strong root systems if one selects for a healthy disease resistant and vigorous plant. I do not believe that I have seen a superior plant with inferior or an inadequate root system. One of my final ‘judgements’ of a plant before potting it up to the next size is almost always that of looking at the roots, and if two or more are similar, the ones with the best root system are selected while the others are culled. I do not see it as part of my job to coddle or babysit if all other things are equal. One thing that I do know is that strong healthy roots make for a strong healthy plant, again if all things are equal.

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This is the exact problem I’m beating my head against now. I’m playing with RRV-resistant species, and making cinnamomeae behave themselves in a garden is like trying to breed a non-suckering blackberry tree. AFAIK, every proven rootstock is vulnerable, except for maybe (sterile?) Baltimore Belle. I’m sure there are ways out of the dilemma, but don’t know enough to make very educated guesses.

Right now I’ve got no solution in mind until my R. damascena bifera x Ragged Robin start blooming. Then I can cross it with cinnamomeae and tell people, “Of course it suckers, it’s an HP!”

So I, too, look forward to hearing what discoveries have been made with regard to breeding for roots. For those of us in North America, I feel like it’s THE biggest headache involved in “going native.”

I could not agree more!!! This is actually one of the criteria I use when culling roses. I make notations on the root system of all my seedlings at the time they are moved to a gallon pot. I also make notations about how easily they root. “If you can’t root them, you can’t share them.” If they have to be grafted, I’m not interested.

It is a curious fact of breeding that traits which are preserved by natural selection can go by the wayside when we stop paying attention, and eliminate the original “selective pressure”.

Burbank (1914):
“The failure to give attention to the matter of fragrance sometimes leads to the cultivation of a special variety of fragrant blossom that has altogether lost its perfume. An illustration of this came to my attention not long ago when visiting the seed farm of the best known seedsman in America. He showed me his new varieties of sweet-peas with great pride; and when I called his attention to the fact that a number of them were totally lacking in fragrance of any kind, he was not a little surprised.”

Beaton (1852):
“The best doctor for our present purpose, is he who can infuse the hardihood of the wild Cape Geraniums into the new race of fancies, for most of the wild ones are much more hardy than the generality of the prize sorts, as I have proved over and over again, having the two growing side by side in the borders of a conservatory wall, where it was very rare indeed to lose a Cape species in winter, and where no winter passed, however mild, without leaving blanks in the large sorts.”

I suppose wild potatoes have no great difficulty growing in clayey soil. But who wants to dig spuds from clay? So, potatoes were cultivated in sandy or other soft soil for centuries. It probably didn’t take long for them to become adapted to loose soil, and shed the specific adaptations for clay.

Some breeders (so I’ve read) bud their seedlings to Multiflora or other stock long before the young ones can show their stuff on their own root. This sort of breeding program leads to varieties that do well when budded. But on their own roots? I wouldn’t bet.


The root-vigor-health connection became obvious to me several years ago. I used to pot everything, of course, selecting the size of the pot to suit the vigor of the seedling as I transplanted them from the seedling tables. After several years of watching those which went directly into four inch pots, I realized VERY few of them ever amounted to anything. Those which immediately went into two, five, even seven gallon cans have always been the healthiest, most productive of the lot, no matter what the cross. Interestingly, the “species” crosses have resulted in some of the more vigorous root systems right off the bat. The germination of hybrid X species has consistently been lower than from hybrid X hybrid crosses, but the resulting seedlings have traditionally had far more extensive root systems, therefore increased vigor than the majority of the hybrid X hybrid crosses.

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Interesting! Were most of those crosses phylogenically distant, or did reasonably close relatives do that too?

Distant. Minis, HTs, floribundas, Teas X (mini X Hugonis) and Fedtschenkoana.

Thanks Paul to put this issue to light.

It is a theme I considered little less than twenty years ago when I undertook breeding no TLC ownroot roses for the southerners.

No tender loving care is for no spray in a climate that successively favor every desease. For little to no pruning also.

Roots are a constant concern of mine I posted about with little echo.
No wonder: for the last century as grafting was the rule, rose breeders were oblivious

And it is a very complex subject so I will only point a few parts.

First: what is a good root system…
Nice looking or performing…

Second: is it selectable when container grown…
Quite questionnable only considering how much root competition is prevalent out of pots and how potting medias are different.

Third: root system is interacting cooperating to competiting with all soil microorganisms be they insects worms bacterias funghi…

Another point is that soils are rather varied as are millenaries adapted species root systems.

Just a few among preliminary points.

A few considerations:

The most adaptable garden rose rootstock: rosa canina is not adapted to containers while less adaptable multiflora thrives.

A few outstandingly rooted species: banksiae, roxburghii, bracteata

A few in garden environment poor rooted less adaptable species: rugosa (chlorosis, drough), nitida (drough), multiflora (chlorosis)

There are no good roots without good leaves. Consistant desease resistance is a must.

Root system architecture is correlated or not with above soil plant architecture.

I grow my seedlings in pots that are ‘too small’ for them and always own-root. IF they survive several years with constricted root systems, doing well despite being pot bound, I consider them winners and pot them up. If they then thrive and take off, I’m a happy camper (as are they, I’m sure). I generally give up on cultivars that can’t survive being in a pot.

Which brings up a question. What IS a good root system? One that can continue to keep the plant healthy despite being limited? Or one that needs room to grow in order to take up enough nutrients to produce a good plant.

One that is efficient and vigorous enough to generate and maintain a healthy, productive plant even in a restricted space is surely bound to be a good system to produce an even better plant once unleashed into the ground. A good percentage of the plants likely to be sold in the future will be potted. What good is one which requires room to develop a decent plant in a potted market?

Root systems in roses vary, just as they do in apples. They range from a mass of fibrous roots to ‘Dr. Covell’s Carrot-rooted Understock’, and everything in between.

Japanese Rugosas are shallow-rooted, thirsty plants. The Russian forms are drought resistant. There is also the matter of pH, texture (sand vs. clay), and mineral content.

Then there’s this old observation:

The Rose Book, a practical treatise on the culture of the rose (1864)
James Shirley Hibberd
Many roses will make a good start in soils quite unfit for them, and when the first flush of youth is over they sicken and become worthless, or die outright; and on the best of soils for general purposes there are some sorts that refuse to make themselves “at home.” Where Gloire de Rosamene does well you are pretty sure to find that La Reine turns consumptive, and vice versa.

A good root system is one that is suited to available conditions. And people around the world have very different ideas about what constitutes a “good garden soil”.

The Hibberd quote is great, Karl, thank you! Jeri Jennings can grow Gloire de Rosomanes to beat the band in her Camarillo, CA garden, but La Reine stinks there, as it does here, too. Except for several found roses which may well be La Reine, such as Crestline Mulberry, which appear to have the vigor and adaptability the La Reine in commerce appears to lack.

I found those seedling which sit in the seedling trays and are covered with PM are prime suspects of a bad rootball. When lifted the root mass may only extend out 1 inch from the plant stalk, where those which are healthy, root length is 2/3 the length of the seedling or even more. My days, waiting for seedlings to so call catch, up are gone as down the road they present problems. One thing I have heard, some major breeders develop a cultivar which may struggle on its own roots and look sickly and then graft it onto vigorous rootstock to make it viable. I have a climber seedling which germinated 7 months ago, has a height of 6 feet and flowering so would gather its roots system is functioning pretty well. One of my prime traits which I breed for is vigour and it is not possible without good roots.


Absolutely, Warren! That is what I observed several years ago and it hold true every year. There can’t be a decent plant above ground without a decent one below. That is the prime reason why so many roses introduced from the 1920s through the end of the Twentieth Century make such rotten own root plants. Some root and grow well, but many don’t. Why should they? No one ever tested them own root. They only had to bud easily and produce an acceptable level of Grade 1 plants on the stocks of choice.

I mentioned how I breed for vigour above. I was talking to Hans from Biercreek and telling him about the bud wood I sent to Belgium. It took 12 days, and by the time they arrived in Belgium, most of the bud wood had developed callus.


Depending upon the stage of maturity, the genetics and temps, callusing in transit isn’t uncommon, Warren. I’ve received cuttings from people all around the country which had callused and vice versa.

Warren, You make a good point regarding PM and the correlating lousy root system. Almost without exception, (note the almost) most PM’d seedlings do not have a good, let alone a great root structure. I have a bunch (I kept two specimens from each differing mother plant and Joe B had sent me some very viable pollen) of Prairie Peace offspring that are sorely in need of potting up, and the notable thing about them is that not one of them has showed any complaints about being crowded, root bound, although they have been dry upon many occasions, and totally grown way beyond the size of the pot. One of them did go dormant, turning a deep crimson, which just happened around Nov. 15th, and all the rest are still a very nice deep green with no brown outs or burnt edges. The root structures of these plants were amazing when they were potted up from their seedling cups over a yr ago without exception. Although several of my 2 and 3 yr old seedlings did show some blackspot when I went out of town several weeks ago and fully half of my roses were starting to show signs of forced dormancy, (I rely on a teenager to water when I am gone and although most survive, not many of them thrive) not one of the PP seedlings showed any negative aspects of the lack of watering, even though they are all in a full sun facing westward position. Good root systems are definitely something every serious hybridiser should be looking for. Kim-Your note about many 20th century roses is so true. I was trying my hand about 7-8 yrs ago at rooting roses and I decided to root many of the popular roses of the 70’s to the 90’s. Most of those are dead now, just because when they became stressed in the least, they gave up and failed to thrive to the point of being pulled. My alkaline soil is definitely part of the problem but I think that the root systems did not adapt well to less than ideal conditions.