By Danielle Smith A Pennsylvania partnership is marking a major milestone by planting its 10 millionth tree in the Chesapeake Bay watershed. A celebration May 26 in Hummelstown marks eight years of work to improve water quality and restore streamside habitats across Pennsylvania’s portion of the watershed. The Keystone 10 Million Trees Partnership launched in 2018 with a goal of planting 10 million trees across the state’s portion of the Chesape…