Earlier this year I planted two Tess of the D’urbervilles climbing roses in 20" pots in my garden. These roses grew to about 3' high this year and began wrapping around the trellis that I had setup for them. Winter is now fast approaching, and although they are rated for zone 5, and I live at the border of 6a/6b (zip 15317), being in pots I worry for their safety. Especially since the last 2 years we had extended periods of subzero temperatures.
Most articles I find online recommend various methods of winterizing that seem impractical. As they are potted I can't realistically pile mulch around them. As they are climbers and attached to the trellis I cannot move them inside (nor would I have room anyway).
I had considered using some of the same methods I use on my Windmill Palms (enclose them in plastic sheeting, wrap Christmas lights around them or lay a warming pad on them to run during the night), but I thought it made sense to see what the 'standard of care' was before committing to any of that.
How do others winterize potted roses that cannot be moved? Also, is it even necessary with this variety in my area?