Distinguish crown thinning from crown reduction and give examples of when to apply each.

• A. Crown thinning reduces density while maintaining height.
• B. Crown reduction trims branches to reduce overall size or clear obstructions.
• C. Crown thinning reduces density while maintaining height; crown reduction trims branches to reduce overall size or clear obstructions.
• D. Crown thinning removes entire limbs; crown reduction only trims small twigs.

Answer: (C)

Crown thinning versus crown reduction are two pruning goals that achieve different outcomes in a tree’s canopy. Crown thinning is about light and air, not size. It selectively removes interior and crossed branches to open up the crown, which reduces overall density while keeping the tree’s height and width largely the same. This helps with light penetration to the understory, improves air movement to reduce disease pressure, and often enhances the tree’s natural form without making it look smaller.

Crown reduction, on the other hand, is about the tree’s size and clearance. It shortens selected branches, which reduces the overall size of the crown and can help clear obstructions like buildings, roofs, or utility lines. While the tree may retain its general shape, the height and width are decreased because the branches themselves are shortened.

In practice, you’d thin to relieve interior crowding and improve canopy health, while you’d reduce to fit the tree under a structure or within a space you need to clear. The best option describes both ideas: thinning reduces density without changing height, and reduction trims branches to decrease overall size or clear obstructions. This combination captures the distinct purposes and typical applications of each technique.