The Orleans Rose-related polyanthas sport freely. (Check out thread linked below.)
I've also had a climbing sport of Europeana that has double the petals and real height.

With the Orleans kin, it must be genetic; with Europeana it was from rooting a very thin stem and then in the second year, a six foot cane emerged.

My guess about the Knock-out like-color sports is that anytime hundreds of thousands of clones are made, there will be some variation, and they've taken it and run with it.

Here is a link that might be useful: My comments on Orleans in this thread

I have many many roses and have never experienced a sport. All my roses that are sports have reverted at times.

I have never had a new sport either, it is the roses that are known for this that do this; F J Grotendrost, Pink F J Grotendorst, Winchester Cathedral, Mme Pierre Oger, Baron Girod de l'Ain, I think this is all. They sort of revert to their origin or sport to the pink version rather often.

I got a sport of 'Gardens Of The World' that I managed to root. GOTW is kind of an obscure HT (Christensen, 1993) that is a pink and white blend. My sport is an orange and white blend. It's grown into quite a good plant as large as the original. The flowers have never reverted back. It must be the only one in the world. That's kind of fun.

And of course 'Mary Rose' has sported to 'Redoute' and 'Winchester Cathedral', and my 'Redoute' has reverted to 'Mary Rose' from time to time. Also got a couple of Yellow Tamoras but never bothered to root them. I think the Austins are good at sporting.

Also getting 'Old Port' flowers this year with white polka dots--I can't tell if it is a sport or some sort of strange phenomenon. I wish it was a sport, it's cool!

There's a Camellia that is famous for sporting, I think it's 'Chandler'. There are about 10 different sports of that particular Camellia, all beautiful. My Mom & Dad had a row of them that started out all 'Chandler' and they ended up all sports, sometimes 2 or 3 on the same plant, for many years.

I have a huge Alba SemiPlena that has several canes that blossom pale pink. The canes are branching from two larger canes that also blossoms the "regular" way, so I know it is not a rootstock.

My Cécile Brunners always sport to the spray form and I had it go the other way once-I took come cuttings of Bush Cécile Brunner and they grew to short intensely thorny extremely floriferous bushs but I lost them when I moved..they were more fragrant as well-strange..like everything condensed down...nothing stable otherwise.

patricia

Variagata di Bologna is sporting several different versions this year-so far nothing is blooming on it that looks like the original. Some of the roses look like Variagata di Bologna Rouge, named by Mike Lowe. Some still have a splash of white.
So far, I'm not minding. VDB didn't like Montana too well, and didn't do much. This new versions seems to have more heat/dry air tolerance.

Back in the fifties I grew the floribunda Jiminy Cricket, a brilliant tangerine orange flower with reddish green canes. One cane in the middle of the bush developed and had the usual reddish green coloration on one side and a medium green coloration on the other. There was a distinct line of demarcation along the entire length of the cane. One half was green and the other half the usual reddish green. As branches developed off the cane, those on the reddish green side developed that color with the usual tangerine orange flowers and branches growing from medium green side developed entire medium green branches with medium yellow flowers. I was too much of a newbie in those days to know what to do though I did recognize it as a sport. Today I would have gotten my plastic bottles out and made cuttings!
Jim

I have 'Rose de Resht' plants that push 7-8 feet tall, while others stay 2-3 feet high - I'm not sure what to call this phenomenon. Otherwise, I haven't personally had clearly identifiable sports yet, either.

My friend's Grandmother's Hat sported a light pink version that is probably "Larry Daniels." He's also noted a single sport of New Dawn and a pure white Chloris - he seems to inspire the unique (actually, he just watches his roses very, very closely)!
Anita

These responses are really quite interesting. Roses are really cool.

Robert

Possible reason why Cemeteryroses' friends has had several sports. This theory was something I read in ORGANIC GARDENING AND FARMING MAGAZINE decades ago when the originator was editing it.
Apparently farmers had noticed that there were certain areas in their fields where the plants where known to frequently mutate. Testing showed that in these areas there were (I believe-geophysicists help me out) electromagnetic fields either entering or exiting the earth's surface. And in the " hot spots" the forces were so strong that it encouraged genetic mutations in the plants. Apparently these waves enter and exit in specific areas around the globe. They were detected with suitable meters which registered the increased forces. Sorry I am not more specific on the details but it was over thirty years ago- they ran a series of articles on the phenomenon then it died out. Maybe someone can pipe in with more knowledge of the forces than I have remembered.
Jim

I've had one sport that we've rooted from Madam Joseph Schwartz. It resembles Duchess de Brabant but has more petals. The plant is about 4 years old and has been stable to produce the same from cuttings.

I've had several sports that show up that are already in commerce..Gruss an Aachen sports Pink GaA and a pure white..Winchester Cathedral sports Mary Rose and Mary Rose sports Redoute. I did have one sport on SDLM Rouge last year that was a perfect match for SDLM.

Jim, your half and half rose cane is called a Chimera-dont be sad because those are famously unstable...an as for elecromagnitism...I used to live near a huge power line -the feed from a Dam and I had lots of sports in my perennial garden. I always wondered if it was all the electricity..but also of the 5 houses there 4 people got cancer so I dont think I am going to seek a powerline to plant under....well one lady smoked but still...patricia

Jim,

I do think you're right on the money. I believe there are certain "factors" that can encourage sporting...also, certain roses are going to have genes which are more likely to be encouraged to sport under favorable sporting conditions. Perhaps someone has studied this phenomenon and has written an article tracing the parents of roses that tend to have sports...maybe there's a common denominator rose..who knows?

Robert