We have summer-like, very dry weather with temperatures sometimes above 20°C.
This was sold to me as Rhamnus californica, but it looks like your plain old Rhamnus frangula aka Frangula alnus. Though this one is definitely different than our native species because it’s (semi-)evergreen. We will probably find out this year, there are flower buds, the berries will tell.
Rhaphithamnus spinosus on the other hand doesn’t seem to be very hardy. Everything above ground-level dies back and the plant doesn’t want to be a ground-cover! Though it is flowering for the first time.
Another slender plant from New Zealand that came back unscathed like Olearia is Hoheria angustifolia. This one was only covered at the base, so it was withstanding th full force of our minimum temp of -11°C.