Samaritan Jo and Giselle are both relatively new clematis, both introduced to the market in 2013, so I don't know if you will get much response on those specific plants. I planted SJ last year also.

In general I have had not problem with any clematis not growing, regardless of weather, though sometimes mine get eaten by voles. For most clematis (mine are usually planted as second year cuttings) I get a few flowers the first year, a somewhat better show the second year, and it looks great by year 3. A plant in a gallon or larger pot will look great by the second year IME. I find all clematis seem to develop at about the same rate as far as floral show.