I purchased a herbacious clematis from Collector's Nursery in Washington State recently. It is labeled "Clematis fremontii." However, it isn't listed in The American Horticultural Society's Encyclopedia of Garden Plants. Has anyone ever heard of Clematis fremontii aka Prairie Clematis? Possibly it's known by another name? Collector's Nursery says it is native to Missouri, Kansas and Nebraska. Thank you for your help.