Richard Hawke is plant evaluation manager at the Chicago Botanic Garden, where he conducts long-term trials on dozens of ornamental plants. For the past 22 years, he has evaluated more than 200 clematis varieties, then tabulated the results of those available today for purchase by gardeners.
You'll find Richard's top picks and why he likes them in "Big Blooming Clematis" in the July/August 2012 issue of Fine Gardening (#146). We couldn't print the full results of his study in the magazine, but we can offer many of them here as a download.
Excellent point Echinacea. As a new clematis obsessed person here, now I wondering if there are any lists of favorite long bloom time varieties ? I'll need to keep my eye out for that.
I finally remembered o pick up a copy of that Fine Gardening, the magazine looks as good as I remember and not so same old thing as it had become. I had a subscription for years, but dropped it becasue nothing looked new anymore. They must have some new people there.