This is a garden cultivated Clematis which matches very closely Clematis viorna. However, this is an extremely variable species and sometimes hard to identify 100 percent sure; plus, hybridisation is possible, both in the garden and in the wild.
Very handsome with lots of bell shaped purple flowers over a long period in the summer.
Germination: sown in the fall or after cold-moist stratification in the spring. Some Clematis species germinate faster than the others; more info on the International Clematis Society website.