handful of chromosome counts

I haven’t been in the lab counting chromosomes in awhile, but last night had some fun and got a few I had waiting done. Here’s what I learned:


Adelaide Hoodless

Golden Horizon

Souvenir de St. Anne’s (Not a surprise as it is a sport of a known triploid)

I’m not too surprised Adelaide Hoodless is triploid. It seems to have low female fertility. It seems like a lot of the landscape roses on the market are triploid (all Knock Outs, most Flower Carpets, most Meidilands, most Oso Easys etc…). It seems like it is a good compromise between the generalized traits associated with ploidy. At lower ploidy there tends to be higher growth rates and branching and at higher ploidy larger, thicker plant parts. I suspect breeders to some extent have indirectly selected for roses that are triploid because of the ornamental appeal/balance between such traits associated with ploidy and also a trend for lower fertility in essence helps the rose self clean and tend to rebloom faster in the landscape.



Thanks for that info, David!

I attempted to breed ‘Golden Horizon’ last year since it is one of the strongest deep yellows I have ever seen. It set seed fairly easily (didn’t accept every pollen I put on it) and I would guess that its seed germinated at a rate of about 30%. I currently have a small crop of seedlings of three crosses that are maturing nicely. I’m very interested to see if the intense yellow follows the seedlings.

Question: in modern roses, are tetraploids generally less vigorous than diploids? I have a number of tetraploid crosses that seem to take quite a bit more time to build up into a good-sized shrub compared to some of the diploid seedlings I grow.

By the way, I have a group of ‘Golden Angel’ X ‘John Davis’ seedlings from last year that are about to flower for the first time, and they are VERY attractive plants with wonderful foliage and branching habit. So far, out of 12 seedlings, two appear to be yellows!


PS: "Candy-O Vivid Red’ has started to flower and it is very attractive. I look forward to seeing it build into a mature shrub. Kudos!


Do you have counted “Horcoexist”. I just bought a poted one and wonder a its ploidy as its pedigree is all tetraploid while it looks as a thin small parts diploid.

Do I recall correctly that ‘Cardinal de Richelieu’ is a triploid?


Yes, it is. Some have reported getting offspring from its pollen, but I’m skeptical about that.

Hi David,

I was thinking that you had already determined that Adelaide Hoodless was a triploid, but it was Alexander Mackenzie that you had.

I was wondering if you were leaning towards creating triploids deliberately for landscape purposes? I created some triploids last year more as an intermediary step and not necessarily as the end result. I was thinking of making a few crosses this year to try and create a rose similar to Fuchsia Meidiland but only hardier. It dies back to the ground even with winter protection.


Hi Paul B.,

I’m excited to learn when your ‘Golden Horizon’ seedlings start flowering if the nice yellow can get passed on. Thank you for sharing on the forum what a beautiful yellow GH is!! I ordered some and am really enjoying them. I agree Paul that it sure seems the higher ploidy seedlings seem less vigorous in general. Often in casual reading and such it seems that the impression gets made that since polyploids have larger plant parts they should generally be more vigorous. It doesn’t seem to generally be that way. Good thing there are usually exceptions to most trends and we can find some vigorous tetraploids.

I wish I had a ‘Horcoexist’ to count. I don’t recall off the top of my head reading about the ploidy of ‘Cardinal de Richelieu’ being reported. Maybe I can count it someday. I don’t have one anymore. Perhaps I can see if there is one at the MN Landscape arboretum.

Hi Paul G.

I would sure love to lean more towards triploids for landscape use. This year will hopefully be the first year in a few years I will hopefully be able to make a significant amount of controlled crosses again. It’s been hard moving all my roses and waiting for them to recover. I’m hoping to use some of these more fertile, disease resistant triploid landscape roses as pollen parents on my hardier shrub seedlings that are primarily tetraploid. There should be a good percentage of triploids out of it. In pollinations involving 4x females x 3x males I got about half 4x and half 3x progeny. Leen Leus got well over 90% 4x offspring. Perhaps she has heavier pollen application techniques that I use and the 2x pollen grains outcompete the 1x ones to get primarily 4x offspring. In potato it was found that pollen tubes from 2x pollen was more vigorous than 1x pollen.

Take Care,


Hi Fara,

Yes, Cardinal is triploid. I tried several years to get offspring of the triploids Cardinal de Richelieu and Mme Alfred Carriere by using them as pollen donors.

I got quite excited when I finally managed to raise a few seedlings from those crosses, however in the meantime I convinced myself that these were parthenocarpic.

To create apomictic seedlings experimentally pollen might be sterilized by radiation. Using naturally sterile pollen works apparentely also in starting apomictic processes in the hip parent.

A certain percentage of seed might be parthenocarpic anyway?


I’ve gotten seeds from crosses using Cardinal de Richelieu as a seed parent, but none have sprouted so far.

That is very interesting. Does that mean your Cardinal produces hips ?

I have never seen any on my plant, and I also never heard from anyone else having hips on CdR.

Of course a very old cultivar had a long time to accumulate mutations and might have split into several closely related forms.

Who was the other parent of your seeds?



Theoretically, there should be 50% 1n gametes and 50% 2n gametes from a triploid, so I would have expected the results that you got. There probably is a difference in the vigor of the pollen and/or pollen tubes between different plants and that is why you and Leen are getting such different results.

I used several triploids this past year as pollen parents with fairly good results. I used Fuchsia Meidiland and Bonica. I had better hip set and seed germination from Bonica than from FM. I had only one seedling from Morden Centennial OP x FM cross last year. Several years ago I tried FM as a seed parent without any luck and I grew some OP seeds from it as well. There weren


Yes, it produces hips readily. The other parent was “Fa’s Marbled Moss” (which I cross with everything because really, you never know…). I got only three or so seeds per hip, and none sprouted. Hopefully that was just mishandling on my part, and I’m trying the same cross again this year.

After about 5 or 6 years of placing mixed pollen on Cardinal Richelieu I finally got hip set. From 3 hips I got six seeds. Three germinated but two quickly gave up the spirit. One survived and has done well. It’s a very double blush cream. I was extremely careful in tracking the hips, seeds and seedlings of the Cardinal to insure I would not make labeling mistakes. Prior to last year I would have completely agreed that the Cardinal was totally sterile.

Hi Fara,

might be a question of climate whether CdR is able to reproduce. I found a paper from 1960 stating it to be completely sterile in the UK and this is a citation " Thus although Cardinal de Richelieu has never set a hip outdoors in the eight years under observation at Bayfordbury, Sam McGredy tells me it will do so occasionally under glass."

The complete paper can be found at http://www.bulbnrose.org/Roses/breeding/Rowley/Rowley_Triploids.html

I am living close to the border between Germany and the Netherlands, so my climate might match Great Britains. I have to get a green house

; /


Hi, Ulrike,

I’m right up against the Rocky Mountains, at about 1600 meters. I’ll have to make careful notes this year on how CdR does, but I’m determined to get offspring from it! (And from Reine des Violettes!)


You have a much better chance of getting offspring from Reine des Violettes. Might I also suggest that Rose de Reschet is quite fertile (pollen better) and has the ability to breed colors like Reine des Violettes? I have a seedling that is Rose de Rescht X Tradescant and is a spooky bluish/grey/purple color that you would make you squeal. I’ll take a photo when it blooms.


Hi Fara,

a place at an elevation of 1600m, that might be quite harsh at times. Your CdR seems to be a very determined unusual plant. Just thinking: it might have changed its ploidy. Wish you good luck with it. Let us know, when you have your first seedling from it.

Cheers Ulrike