Q.How fast does japanese lilac tree grow?
I would like to plant a Japanese lilac tree for privacy in a neighboring garden. Soil is light and I live the northern Minneapolis suburb in Minnesota. I think that my zone is 3.

The Japanese Lilac is hardy down to zone 3. It has a medium growth rate. This is a great tree to enjoy in the spring when nothing else is blooming in our gardens.
I also garden in MN and you are zone 4a or 4b.
Here is a great link.
https://www.gardeningknowhow.com/ornamental/shrubs/lilac/japanese-lilac-information.htm