Dear Dr. Universe: How long can trees live? -Jessy, 8, Seattle, WA

What kinds of trees are in your backyard? Do they have pinecones? Colorful leaves? Pods with seeds? Tell us more or send a picture to Dr.Universe@wsu.edu.

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 building the pyramids,” said my friend Kevin Zobrist, a forester at Washington State University.

Zobrist knows a lot about different trees and told me a bit about bristlecone pine trees.

By the time the pines are about 5,000 years old, they will stand 60 feet tall with a trunk that is nearly five feet around. If we were to cut into the trunk, we could look at its growth rings. Each ring would signify a year of its life. We would have a lot of counting to do.

On my hike, I noticed some of the trees’ young pinecones were purplish-pink. Eventually they would turn brown and fall to the ground. I spotted a few old cones by the tree. They had that fresh pine scent.

I looked up at the branches that twisted and stretched like arms up to the sky. I wondered how on earth these trees were able to live such long lives.

Zobrist explained that bristlecone pine trees are tough and have adapted to their environment. They are equipped to deal with drought, extreme climates, and insects that might cause serious damage if they attack.

For example, the tree can actually shut down or go dormant for a while, if conditions are too harsh. This helps the tree survive for thousands of years.

“They teach us that nature is resilient,” Zobrist said. “They teach us that nature can carry on.”

Of course, not all trees live quite as long as these pines. But many live longer than humans and us cats.

The redwood trees of California are about six times taller than the bristlecone pines. Some of them have been around for nearly 2,000 years.

Even when a tree dies, it finds a new life. Creatures and plants on the forest floor are counting on the trees to get old, die, and fall. They can use the fallen trees as their home or for food.

It’s been said that trees are our planet’s lungs. They help make the oxygen we breathe and keep life thriving on our planet. I took a deep breath of the mountain air and said a quick thank you to the trees before heading down the trail, on to the next adventure.

Sincerely,

Dr. Universe