Q.black sandcherry shrub planting
How close to the property line should black sandcherry shrubs be planted? I’m not sure how big these shrubs get or how quickly they grow and want to provide enough room so that they do not grow into the neighbor’s yard.

According to the following extension article, purple-leaf sand cherry shrubs mature to a width of 6-8 feet and a height of 7-10 feet.
https://urbanext.illinois.edu/ShrubSelector/detail_plant.cfm?PlantID=363
For more information on plum (purple) leaf sand cherry, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/sand-cherry/purple-leaf-sandcherry-info.htm