I'm looking for an evergreen vine that is more hardy than star jasmine. I am trying to create a privacy screen about 8 feet high, 2 feet deep. My star jasmine has lost its leaves the past two winters, in spite of having wrapped the entire plant including the roots. Is an evergreen clematis a better alternative? Will it keep its leaves in the cold snaps we've had the last 2 winters? I am in Portland, near Mt. Tabor, elevation 200 ft. plants are located in a north-south row on east side of my house, in the middle of a 15 foot space between houses. Summertime sunlight is about 4-5 hours.