I looked up some information about rosehips. I can't remember where I read it now, but it said that all rose varieties grow fruit, however some grow larger and sweeter than others. It went into a long list of varieties with botanical names and, I have to admit, it made my head swim a little bit. I decided to just let my roses grow this year and see what happens.
The results were very interesting. All of the bushes grew visible rosehips, but some were larger than others. The largest and plumpest rosehips were on the bush that I watered the most over Summer, the Flamingo. The smallest and saddest looking ones were on the bush I only watered a couple of times (variety unknown). It's the one furthest from the tap, and it always looked to be doing fine when I checked it, so I didn't bother to water it.
It makes sense, when I think about it, that roses would grow better fruit when watered more, just like my fruit trees. I'll be more conscientious with that next year. I'm not sure yet at what point the rosehips should be harvested; I'll have to do some more research on that.
The only drawback of growing rosehips of course, is that the gardener has to put up with an ugly-looking bush for a few months. But it's just a reminder that nature isn't always pretty.