The difference between Caohua Pear and Yahua Pear

A kind of grass flower pear and sub flower pear. Sub-flower pear belongs to non-mahogany, which is the general name of many kinds of wood. generally speaking, sub-flower pear mainly refers to African stinky pear, and grass flower pear is a general name of rosewood pear trees, including 7 tree species. What is a grass flower?