Can I grow a dwarf Lilac in a large container in my apt. balcony, successfully enough for it to flower every year? Do I cover it lightly with a thin gunny-type covering (Home Depot) during winter as it needs the cold to bud?, or do I cover it with a thicker covering, pot and plant and underneath as well to keep it from getting frost-bitten? Simply dying to have a flowering plant on my balcony that does not cost a lot and then dies after a year or two (senior ). Balcony facing North East.
Thank you for contacting the Toronto Master Gardeners with your question about growing a dwarf lilac in a container on a north/east facing balcony. Dwarf Korean lilac is a reasonable choice for our Toronto climate. Depending on how high your balcony is, you may have harsher winter conditions (for example; colder, windy) than at ground level. Lilacs bloom best in full sun (6-8 hours / day). Assess your balcony sun pattern to determine how much light you get. If sun exposure is marginal, your lilac may bloom more sparsely. Consider a pot caddy to easily move your plant around to the sunniest locations if needed. Select a good sized pot (60 cm /24 inches) with drainage holes to ensure plant roots have space to grow and excess water can drain. Larger pots hold more soil, which will help to insulate roots in winter. Some pot materials withstand freezing better than others. Check out the Toronto Master Gardeners Guide to Container Gardening for more general information here.
The main threat to overwintering plants is freezing and thawing. Measures to avoid freeze / thaw cycles include placing plants in a shady location. This avoids pots warming up on a sunny day in January and then freezing again. Insulating pots with mulch (straw, leaves) on the surface, and styrofoam, straw, bubble wrap or thick cardboard around the pot can also be helpful. Protecting plant branches with burlap can help to prevent desiccation from ice and wind. Elevating the pot on a wood pallet or styrofoam can provide insulation from below and protect your balcony surface. Another option is to set your pot inside a larger pot and insulate the space between them. The following website has further information that may be helpful How to protect potted plants.
If you determine that your location doesn’t get enough sun for a lilac to bloom well, consider a Low Bush (aka Northern) Honeysuckle (Diervilla lonicera). This small (3 feet) deciduous shrub has delicate yellow flowers in summer and nice fall colour. You can read more about it here.
Best of luck with your balcony gardening!
Sept 20, 2023