We recently built a raised deck (right side of picture) and now looking to plant tall trees that would grow high above the wooden fence to allow for privacy. Would a pagoda dogwood or white cedars work within in this space and how long until it grow tall?
The pagoda dogwood, Cornus alternifolia, is not considered to be a quick grower, but will eventually reach approximately 20-25 feet at maturity and will live for approximately thirty years. It makes a stunning statement with its beautiful horizontal spreading habit which would eventually screen your deck. You would need to be certain that you had the space for it.
White cedars would work as well, and these evergreens do have the advantage of providing privacy in all seasons, and taking up less space with their columnar habit. Once established, you could expect them to grow approximately one foot per year.
If you are concerned with the spread or width of the tree you plant, and if you worry that the pagoda dogwood at maturity may be too large for the space you have available, here are ideas from other posts, the first for a privacy screen in a small space: https://www.torontomastergardeners.ca/askagardener/trees-for-privacy-in-a-small-space/ and the second which gives suggestions for tall narrow plants for hedging: https://www.torontomastergardeners.ca/askagardener/hedging-for-toronto/
Another option which you may not have considered, is a mixture of columnar trees for privacy interspersed with tall trellis panels on which vines could be trained. Landscape Ontario’s website provides a list of vines that might work for this purpose: https://landscapeontario.com/climbing-vines.