This article provides a pretty good review of rose biology:
Jim, thanks for posting this link.
As a result of reading this article, I am going to toss out the Rosa Canina seedlings I germinated a few months ago.
I was going to use them as rootstock, but since reading this article, I understand they are regarded as weeds here in New South Wales.
Multiflora is a weed here in the US, but it makes a great rootstock for most soils. I’m not sure why you’d want to toss your rootstock. You’re not planning to grow it except as rootstock.
I’m not sure you’d want to use canina in Sydney as it is really more of a cold weather rootstock. It’s the preferred rootstock for northern Germany, for instance. Judging from the climate fortuniana and multiflora might be better, although if canina does well there then go for it. Plants I’ve grown on canina did well here in Connecticut (zone 5b-6a).
Does R. Canina produce suckers from its roots?? I dont know as I have no experience with it.
Peter, I believe that in the USA some states have actually outlawed the use of multiflora as a rootstock because of the weed potential.