I am wanting to plant some hardy small shrubs (maybe flowering) on my balcony. Zone 4. I have a dwarf lilac that seems to be doing well but the Japanese Barberrty . . . Any suggestions
Thank you for contacting Toronto Master Gardeners.
Balcony shrubs are perfect for adding colour, greenery, pollinators and privacy to your personal landscape. Below is a link to a Toronto Master Gardener answer to balcony shrub planting:
A Gardening Guide with comprehensive information on Container Garden is available on the Toronto Master Gardens website:
Balcony gardening in containers is different than an in-ground garden. Overwintering for plants in the ground is easier because of the amount of soil protecting roots. During freeze/thaw cycles, soil can absorb some of the shock to the plants. With containers, there is not much buffer zone of soil and planting in larger containers helps add more soil protection. The best containers for overwintering are plastic, composite, metal and wood pots. Ceramic, lightweight foam, and terracotta pots are the most likely to crack under the freeze-and-thaw pressure of our winters.
The main issue with overwintering on a Zone 4 balcony are the effects of wind, snow, ice, reflective hot sun and shade during winter days. Container plants may not survive in spite of their Zone 4 rating. It is suggested that Zone 3 or Zone 2 plants would be hardier and better able to weather the winter. The hearty dwarf Lilac (Syringa) is a Zone 2 shrub.
Winterizing the exteriors of the containers could also help plant root systems survive. There are a number of insulating products including burlap, garden wool, insulated bags and tarps available online. Covers should wrap containers from the floor up and if possible, huddle the pots together in a protected corner of your balcony. Here is a link with good tips for overwintering containers.
Some suggestions of small stature shrubs for Zone 2 or 3 are:
1. Kelsey Dwarf Dogwood (Cornus sericea ‘Kelseyi’) grows 2 – 3 feet high with spread of 2 – 3 feet. Globe shape with white flowers and red stems in winter. Zone 3.
2. Cool Splash Dwarf Honeysuckle (Diervilla sessilifolia ‘Lpdc Podaras’) grows to 3 feet high with 3 foot spread. Variegated foliage and yellow blooms in July. Zone 3.
3. Dwarf Broom (Genista lydia) is 18 inches high with 3 foot spread. Pendulous branches with golden yellow flowers in June. Zone 3.
4. Mango Tango Potentilla (Potentilla fruticosa ‘Uman’) is 2 feet high with 2 foot spread. Mounded growth habit with bi-colour flowers (orange base with red centre). Zone 2.
5. Dwarf Russian Almond (Prunus tenella) is 2 – 3 feet high with 2 – 3 foot spread. Globe shape with rose-red flowers in May. Fuzzy, almond-like fruit follow. Zone 2.
6. Rose Daphne (Daphne cneorum) is 10 – 12 inches high with 4 foot spread (width can be controlled in a container). Broadleaf evergreen with highly fragrant deep rose flowers in late May. Zone 2.
The link below is a PDF of cold weather shrubs from the City of Brandon, Manitoba. Average low temperature there in winter is -20 Celsius.
The Toronto Master Gardeners website has many overwintering suggestions for containers in their search feature.
Hope you develop a colourful and hearty collection of shrubs on your balcony.
May 4, 2022