Insulated Outdoor Container

(Question)

I would like to build insulated planters to sit on my outdoor deck in Mississauga, and into which I plan to plant a vine to grow up to the trellis above. (I will provide appropriate support for the vine to twine up to the trellis). I want to leave the planters in place over winter. The vine I am currently considering is Dutchmans Pipe but I am open to other suggestions. Location is in full sun. Could you give me direction on the size of container to build, the amount and type of insulation and a vine recommendation. Thank you.

(Answer)

Thank you for contacting Toronto Master Gardeners.

Overwintering pots on a balcony can be a hit or miss thing. In the last few years winters have varied so much it can be hard to predict what the weather will be. The most damage is usually from temperature changes, freezing and thawing. It will be important not to have direct sunlight on the container during the winter to minimize temperature fluctuations. The following link is from our library of questions and talks about insulation of containers.

http://www.torontomastergardeners.ca/askagardener/winterize-ornamental-grass-in-container/

Here are some other helpful sites on container winterizing

Overwintering Potted Plants (Brooklyn Botanic Garden)
Winterizing Container Grown Trees and Shrubs (University of Illinois Extension)

Dutchman’s pipe, Aristolochia macrophylla, is at least a zone 6 in Canada so is unlikely to survive the winter in a container in Toronto.

Your best bet would be to visit your nursery in the spring to see which vines are available. Look for a vine that is hardy to 2 zones colder than Toronto. A zone 3 or 4 will have a much better chance of surviving.  The Nursery staff should be able to help you decide which vines have the most chance of survival and thriving in a container situation. There are some clematis that may have success in your pots if you insulate and protect against direct sun to decrease sudden changes in temperature. With the variety in the weather we have experienced over the last few winters there is never a guarantee the plants will make it through.

Good Luck.