the older, harder, nonliving central portion of wood of some trees that is usually darker, denser, less permeable, and more durable than the surrounding sapwood. Many trees do not form a true heartwood.
pltintern
Christine Song supports both Project Learning Tree (PLT) US and Canada's program delivery and reporting, program research, and communications. Christine holds a Master of Environmental Science from the University of Toronto and and a combined degree with a Bachelor of Science in ecology and zoology and a Bachelor of Science in anthropology from the University of Calgary.
