I just bought two Dwarf Alberta Spruce plants…which I intend to repot into planters that are 7”X7”X7”. I will be placing them outdoors on my balcony (they get south and west sunlight) asap.
I realize they require “well-drained acidic soil”… but I have never known what that is. The closest hardware store to us carries bags of “Alltreat Farms” Tropical Soil… IN CASE THIS HELPS: The info on the bag includes: “Ready to use straight from bag, no additives needed”’ “contains time release fertilizer…”; “Guaranteed Minimum Analysis: Total Nitrogen 0.08%, Available phosphate 0.24%, and Soluble Potash 0.08%.”
I am grateful for any help you can provide. I am hoping to repot asap.
Very best wishes,
Miriam email: firstname.lastname@example.org
The increase in urban sprawl has lead to the increase in condo living and container gardening. The Toronto Master Gardeners have received numerous inquires concerning growing evergreens in containers, entering ‘evergreens in containers‘ in the search bar will bring up a number of our archived posts.
Before starting we suggest you check with your building management for regulations in use of balcony space–safety concerns and weight considerations.
When planting in containers it is recommended to use a commercial soil-less mix formulated for container plants available at your local garden center. Overwintering shrubs 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. In general, when planting evergreens in containers you should choose a pot that is two or three times wider than the root ball of the tree. To provide additional protection to the roots you can insulate your containers with 2″ deep styrofoam on the sides and bottom. Because their roots do not like to remain wet, make sure the pot has drainage holes. Creating a burlap screen around your Alberta Spruce trees will protect them from drying winter winds which causes winter burn.
Ensure that the containers are freeze thaw resistant. Ceramic and clay pots will probably crack as will cheaper plastic pots. This link might be helpful: Dwarf Conifers in Containers
When a plant is grown in a container, its roots are essentially surrounded by air, meaning it’s more susceptible to temperature change than if it were in the ground. Because of this, you should only try to overwinter container grown evergreens that are hardy to winters considerably colder than what your area experiences which in zone 6 Toronto would be Zone 4, or to be safer, Zone 3.
Keeping a potted evergreen watered in winter is a delicate balance. If you live in an area that experiences a hard frost, keep watering until the root ball is completely frozen. You’ll have to water again during any warm spells and as soon as the ground begins to thaw in the spring to keep your plants roots from drying out.
Placement of the container during the winter is another consideration. Ideally the container is placed in a location where the shrubs receive partial sun as opposed to full sun and have protection from the wind. Also avoid leaving the container on concrete or stone as these surfaces conduct cold to the plants. For more information about the care of evergreens in containers please see: Growing Evergreens in Containers