Your plant tags and plant info from the internet may not be accurate.
Let’s start with plant tags. The plants that are at our local nurseries are not all necessarily grown here in Ontario nor are the plant tags necessarily printed here or contain our Zone 5 growing information.
Please keep that in mind and try not to take the tag info as absolute. Japanese Maples in British Columbia may reach 20 feet. Here in Ontario with our winter and shorter growing season, you would be hard pressed to find a 20 foot Japanese Maple.
If you have questions please talk to a qualified, experienced person at your local nursery. I know the teenagers working there try to be helpful but they often will defer to the tag.
If you decide to search for plant information on the internet, make sure you are searching for Zone 5 growing information.
If you have a design from me but are concerned about a plant please contact me.
Most plants I use in my designs I have in my own garden or I have experience with and I can reassure and inform you.