Trees or Shrubs for North Facing Balcony

(Question)

Hi,

I’m looking to plant several small trees/shrubs on my north facing balcony that gets a fair amount of indirect light. I’m wondering what options are best for looks, privacy and low maintenance ie less pruning.

Lastly, any tips on how to plant them in order to survive winter?

Thank you

(Answer)

Hello – Dwarf conifers do well in containers and are a good choice in terms of privacy as they hang on to their needles throughout the winter months.  Note that the term ‘dwarf’ pertains to the mature size of the tree or shrub and can also apply to its rate of growth.  A true dwarf tree/shrub will have a mature size of from 2 to 6 feet and a rate of growth of 3-6 inches annually.

The plant hardiness zone for perennial plants declines the higher up in a building a unit is located. As a rule of thumb, those gardening above ground level in Toronto (zone 6b), should choose plants hardy to zone 4.

Another consideration in selecting a conifer are your light conditions.  Most conifers require full sun but there are some that prefer a part shade location, defined as 4-6 hours of direct sun per day..  I’m going to assume that ‘a fair amount of indirect light’ equates to a part shade condition.

Here are a few to consider that meet these conditions:

  • Gold Cone Juniper (Juniperis communis ‘Gold Cone’), a narrow form, new needles yellow and turn blue-green as they mature, 6 ft. high, 2 ft wide at maturity
  • Golden Mop False Cypress (Chamecyparis psifera ‘Golden Mop’), more rounded form, yellow foliage, 7 ft. high, 6 ft wide at maturity
  • Gentsch White Eastern Hemlock (Tsuga canadensis ‘Gentsch White’), white tips on new needles, rounded form, 4 ft. high and wide at maturity
  • Conica Dwarf Alberta Spruce (Picea glauca ‘Conica’), pyramidal form, 6 ft. high by 5 ft. at maturity

Plant your conifers in large frost proof containers – 2-3 times the diameter of the root ball of your plants.  The large size allows for extra soil that provides insulation during the winter months.  Plastic or fibreglass containers are lighter than clay, concrete or metal. Be sure to use a potting soil rather than topsoil in your containers as it is much lighter and holds moisture well.   Even so a large container of wet potting mix is very heavy. Be sure to check your building regulations for any weight or other restrictions.

Note that while deciduous trees/shrubs go completely dormant during winter, conifers do not.  The needles still need moisture from the roots.  Once the soil freezes the roots can no longer take in moisture from the soil, so you want to make sure the roots have as much reserve water as possible going into the winter.  Don’t stop watering until the soil freezes.  Adding a thick layer of mulch to the top of the container can also help. Winter winds can severely desiccate your container plants so situating the containers away from the prevailing wind or if possible, moving the containers to a more protected spot for the winter can also help.

Have fun selecting and planting your trees/shrubs.

March 12, 2021