I trust all is well with you and your family, friends and acquaintances.
We live on the 12 floor of a downtown Toronto condo with a west facing balcony. Our balcony is only open on 1 side, i.e., the west facing side and gets sun from approx. 11am to 8pm.
We are looking for a dwarf tree or shrub with the potential to thrive in this very hot, sunny environment. And of course, the normal overnight temperatures of Toronto.
thank you, peter pinch
Thank you for contacting the Toronto Master Gardeners.
The percentage of Toronto’s population living in condominiums and apartments increases annually. As a result, growing plants in containers has become immensly popular. There are some important factors to consider before embarking on balcony gardening.
Check with your Property Manager or Condominium Association prior to installing planters or window boxes. There may be site specific regulations.
Wind consideration: Is the balcony sheltered or exposed to prevailing winds or wind-tunnel effect? Wind is perhaps the biggest challenge to balcony gardening–wind will dry out the soil in containers easily–consistent and effective watering is required. And the higher your balcony is from the ground, the windier the conditions.
Size of containers: If you plan to grow perennials, you will need large enough 4-season insulated containers that will withstand the changes in temperature throughout the seasons. Note: You should check with your building management for regulations in use of balcony space–safety concerns and weight considerations. For perennials, containers will need to be at least 40 cm. (16″) in height and width. You may need to consider lightweight alternatives for containers and soil.
Overwintering perennials in containers is one of the biggest challenges faced by container gardeners in our zone, and balcony gardeners in particular. 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.
‘Right plant, right place’ is even more important on a balcony than on the ground–one must consider the recommended growing zone for perennials; select plants that are at least 2 zones hardier than the normal zone [i.e. for Toronto (zone 6a), plants should be hardy to zone 4].
The best trees for containers are small and slow growing with compact root systems. Evergreens that are cold hardy in Toronto will need to be rated at zones 3 or 4 when in a container. Dwarf cypress appears to be a questionable survivor in our climate, however, Chamaecyparis or False Cypress would be a suitable choice and hardy to zones 4 and 5 and there is a great variety of colour, foliage and form available. Because evergreens transpire throughout the winter, they must be kept watered right up until the soil ball freezes hard. Spread out the roots at potting up for all plants.
Lots of varieties of evergreens work in planters,but dwarf varieties and those with slow growth are the easiest. This link might be helpful: https://www.bbg.org/gardening/article/dwarf_conifers_in_containers
Lastly there are a number of archived posts in our website, simply type ‘balcony gardening’ ‘evergreen for containers’ in the search bar located to the right of the page. You might find Evergreens in containers and Growing Emerald Cedar in Container useful.
Acer palmatum or dwarf Japanese Maples grow well in containers with a lovely variety of foliage colour and form, upright or pendulous in habit. You might consider growing hardy roses. Explorer roses are a set of roses varieties that have been especially developed to survive Canadian winters.
Sun loving annuals are also a consideration. Bougainvillea ( Bougainvillea spp.) are tropical vines from Brazil. You can now purchase them in tree form and would make a beautiful flowering addition to you balcony. If you decide to overwinter this plant, make sure to bring it indoors in the fall. Another tropical to consider is Hibiscus. They come in a variety of floral colour and like Bougainvillea this tropical can be brought indoors in the fall.
http://torontourbangrowers.org/img/upload/BloomingOurBalconies.pdf and https://www.canadianliving.com/home-and-garden/gardening/article/7-secrets-to-successful-container-gardening
provides some excellent information.