Rose Sucker or Sport?

I have a white, semi-double flowered climbing rose called Starlight Symphony, which started flowering about a week ago. It is in its third summer now, and probably maximum height, covering half an arch.

I noticed today that it has a smaller, single pink rose that I think looks like a very pretty specimen of a dog rose, which seems to be growing on the same branch that produces the semi-double, large white flowers of Starlight Symphony. I had to stand on a step ladder to get a closer look, and when I have more time I will try to investigate further exactly what is going on.

Obviously if it is a sucker, then I need to remove it at source, or it will weaken the Starlight Symphony rose. If it isn't a sucker, is it some kind of Sport?

 

It's a dog rose sucker, yes. You need to trace the stem back to its source, which will be under the graft union, probably below the soil, and give it a firm tug to yank it off. Best to hold onto the rest of the plant with your other hand whilst doing so.

Don't worry too much if you don't get the whole stem out. Sometimes it's just not practical.

 

You are right, it was a sucker. It was a very long climbing stem with loads of side stems and flower buds, and similar glossy leaves to Starlight Symphony. It was extremely healthy, tough and pretty and I hated getting rid of it, but it would have harmed the Starlight Symphony, which looks a lot tidier now and I can see its main stems and side shoots and flower buds better. I took a couple of cuttings of the dog rose and if they take might plant it somewhere else.

That was interesting, I have never dealt with a sucker before.