I've had 2 engleman ivy for 3 years now. one has grown quite tall and i'm wondering if i'm suppose to cut it down in the fall or spring, or does it grow on previous years growth. I didn't cut it down this year and couldn't tell if it had green growth growing from new shoots or old stuff. i'm in northern Mn and gets extrememly cold. vine is climbing on arbor and is about 13 ft. long/tall. Any information very much appreciated. place i bought them from doesn't seem to know much about them. Thank you.