Hard pruning of virtually any clematis their first season is recommended by most growers and serious clematis gardeners. Many extend this practice to the second and third seasons as well, especially for the hybrids. At the worst, you may delay the bloom season but the benefits are that the plant will develop a very strong root system and generate more stems from the root crown, encouraging a thicker, fuller vine and reducing the potential of wilt and damage from injury or critters.

gardengal148 thank you, that makes a lot of sense, we're just beginning the last month of winter here, so I'll go and prune the last Venosa Violacea back to just 2 sets (4) buds above ground. I'm also trying to get hold a tough white, I had C.Spoonerii - a Montanna, I think - when I lived down south in Sydney but I can't find one for love-nor-money up here. It grew well in Sydney, which has cooler winters than here, but I'd like to try it again. Thanks again and all the best to you.