Likely varies to some degree with species from one individual to another, some being better hip parents than others.

I have an unknown white (someone bought an old place and no labels and I got a sucker...I don't recommend sticking a spino sucker in the ground, spreads) spinosissima, assume just straight species given all it's habits and traits.

It doesn't set a huge number of hips (maybe half of flowers) but it sets them. Of those that germinated, many of them seemed like straight spinosissima (no others in the garden at that time except the diploid pimps like hugonis on the other side of the garden), while others were obvious hybrids with things near it.


in the references there's one "Cross- and self-compatibility in various species of the genus Rosa"

which says
"R. spinosissima L. Ploidy, Ploidy 4x
Pollen fertility 97.7%
Selfed Fruit set 75.8%
Selfed Seed set 58.7%"

which isn't too far off what I'm seeing with mine (just less hip set)

Meanwhile at a public garden nearby there is plants of Single Cherry (and something labeled Single Purple) that produce a lot of hips. Seedlings from those show no obvious hybridity but who knows if they are self or just crosses between the two.