I would like to winterize my two clematis plants. I live in a condo facing east on the 14th level. Each plant is in a resin/plastic tall black container. How do I protect them for over the winter? Do I wrap the container and plant with burlap?
Wrapping your container is a good idea but burlap alone may not be the best material to use. The soil in containers freezes more deeply than soil in the ground and is more susceptible to repeated freezing and thawing. Your objective is too insulate your container as much as possible and loosely woven burlap won’t achieve this on it’s own.
Sounds like your container is fairly large which will help your clematis withstand temperature fluctuations. Moving your container to an inside wall can provide a moderating effect as does collecting all of your containers together. Ensure the containers do not receive direct sun during the winter months as the sun can thaw the surface during the day that then freezes at night.
To insulate your pot, experts often recommend surrounding your container with a wire cage and filling it with a coarse material such as dry leaves. A loose covering of burlap filled with leaves would also work. This approach may not be very practical on a balcony but wrapping your container in bubble wrap would also work and covering the bubble paper with burlap would improve the insulation quality and to my mind be more visually appealing than the bubble wrap.
Don’t cover the top of the container with any kind of wrapping material. It too needs some protection but the plant still needs to breathe. A layer of leaves is a good choice or if you are clearing foliage from other containers you could chop this up and add to the top of the containers needing protection.
Larry Hodgson who is a horticultural blogger living in Quebec City has recently posted a good article on winterizing containers. In particular, Larry notes containers should be slightly elevated through the winter as a thin layer of ice can form under a pot sitting directly on a hard surface and prevent drainage. If the soil can’t drain, your clematis may rot from sitting in soggy soil. You can buy pot feet at most garden centres. Pieces of wood or stones will work as well. I’ve copied a link below to Larry’s full article.
Good luck with winterizing your containers. As always, we Canadian gardeners will hope for a moderate winter.