"Canopy size" refers to the overall dimensions or extent of the foliage or cover provided by trees or plants when they come together to form a dense, overhead layer. Full definition
Canopy size of this Maclaren Quest stroller is quite large to protect the toddler in a bad weather. (pickbabystroller.com)
Modern analyses of satellite images could also show the decrease in individual tree canopy size if trees lost big branches and only regrew them slowly. (earthobservatory.nasa.gov)