Ask Dr. Universe

How long can trees live? – Jessy, 8, Seattle, Wash.

Dear Jessy,

As I was hiking through the bristlecone pine forests of the Sierra Nevada recently, I stumbled upon a tree barely six inches tall. It was growing – slowly, but surely. I was surprised to find this tiny pine tree was already about 40 years old.

Some trees will stop growing once they reach that age. But others live much longer. In fact bristlecone pine trees aren’t just the oldest trees, they are some of the oldest living things on our planet. They can live for about 5,000 years. “These trees were growing when the Egyptians were bui...