Clematis Jackmanii is one of the most popular and widely grown clematis culitvars in Canada. Hardy to zone 4a, I’ve found it to be not only successful but prolific in my zone 3 garden.
It prefers cool roots but flourishes in direct sun, blooming from mid summer into the fall. Mine is at its prime this week, already more than 8 feet tall and covered in luscious 5-6″ purple blossoms.
I trim my Jackmanii to 24″ above the soil in the late fall once it has finished flowering, but if I forget or don’t get it done before snow falls I can do the same in the spring before the new sprouts emerge.
Clematis Jackmanii was originally developed by horticulturist George Jackman of Surrey England in 1862. It can be purchased at virtually any garden center in North America.