I promised a follow-up photo of Clematis x cartmanii ‘Joe’ in full bloom and here it is.
This small clematis from New Zealand makes a gorgeous potted plant, but keep in mind that it is not hardy in a colder climate like Toronto’s (around zone 5b-ish) and must be overwintered in a cool greenhouse. Meanwhile, if you’re looking for climate context, cold hardy clematis that are grown outdoors are only just beginning to put out buds here in Toronto.
Two other varieties, ‘Cassis’ and ‘Vienetta’ also do well in big containers. They are a bit hardier than ‘Joe’, but here in Toronto still seem to require a protected place to spend the winter. My friend Barry (clematis enthusiast) says that if you don’t mind losing a plant to experimentation, it might be possible to overwinter either outside. He hasn’t tried it yet.
Check out Barry’s blog where he talks about how he has achieved the compact, spiral growth shown here (it’s his plant).