Once rooting has occurred, I plan to transfer these Northern White Cedar cuttings to 10-inch pots. I will be acclimating them to direct sunlight in early autumn and caring for them in full sun for the following year. I will be transferring them to their final resting place (privacy fence) in autumn of year two.
My concern is this year’s first winter. My plan is to place some mulch in each pot and keep them hydrated until the first frost.
My question is how to best protect them from the harsh winter and all the snow we get here in Eastern Ontario.
You are to be commended for rooting Northern White Cedars (Thuja occidentalis) to create a privacy fence (hedge) on your property. You want to know what you need to do to overwinter the 10-inch pots during the winter months.
You are aware that it is important for evergreens of any size to be watered (kept hydrated); however, one actually needs to keep watering them beyond the ‘first frost’–they should be watered until the ground freezes.
Do you have a place where you can dig in the 10-inch pots for the winter before the ground freezes? The pots can be situated close together. If that is not possible, they can be placed together above ground in an area out of direct winter sun exposure. The fact that you usually get a lot of snow is an asset–snow cover protects (insulates) plants from the effects of freezing/thawing during the winter months. A mulch of some organic material (for example, shredded/composted leaves or cedar mulch) in each pot would also help to insulate the seedlings as well as to add nutrients to the soil.
For information about planting and maintaining the cedars once you have created your hedge, please see the Toronto Master Gardener gardening guide on growing evergreens: https://www.torontomastergardeners.ca/gardeningguides/evergreens-suitable-for-hedging-a-toronto-master-gardeners-guide/
Good luck with your project.