I live in Toronto (zone 6) and my backyard has tile. I’m planning to plant a climbing hydrangea In a planter box along my East fence. What would the dimensions need to be? Would a 2 ft deep planter be enough? And what would be the length and width? Thank you.
Thank you for contacting Master Gardeners.
Growing perennials including vines in containers has become a very popular trend. Before moving ahead, there are a few important factors to consider. The following information is from a number of our archived posts:
Overwintering perennials including vines in containers is one of the biggest challenges faced by container gardeners in our zone. The freeze-thaw cycle is the main problem: that is, the melting of the water in the container’s soil during sunny or warmer spells, followed by freezing when the temperatures dip again. This is what kills a plant’s roots over the winter.
Your most important starting point is the container itself: it should be as large as possible (the more soil it can contain, the more insulation it will provide.” Ensure that the containers are freeze-thaw resistant. Ceramic and clay pots will probably crack as will cheaper plastic pots. You will want to insulate your planters. Sheets of styrofoam positioned around the planters would be helpful. Or you can place bags of leaves or mulch around the planters to protect them from the heat of the sun. In addition, you should add a four inch layer of mulch on top of the soil. Remember that the soil must be moist before the winter sets in. Remove the coverings once the weather warms.
Climbing Hydrangeas ( Hydrangea anomala subsp. petiolaris ) grows in zone up to zone 5 . The rule of thumb for over wintering perennials in planters is that the plant should be hardy one to two zones colder than your zone, which in this case is 5. A vine that is hardy to 2 zones colder than Toronto such as in a zone 3 or 4 will have a much better chance of surviving. You might have more success with a hardier native vine like the Virginia Creeper.
You may wish consider an annual vine. There are many benefits to planting annual vines: annuals, unlike perennials which have a limited flowering period, are bred for continuous flowering throughout the growing season. Also, by planting annuals, winterizing the planter box is not necessary.
Below is information on both climbing hydrangea and Virginia creeper.