Bristlecone: The Secret Life of the World’s Oldest Tree

Living for more than five thousand years, ancient bristlecone pines are the oldest trees on Earth.

Author: Alexandra Siy
Illustrator: Marlo Garnsworthy
Format: Hardcover
Pages: 32
Ages: 7-12
Grade Levels: K-4
Lexile: 880L
Hardcover ISBN: 978-1970039030
Price: 18.95
Where to Purchase:

“Inherently fascinating, impressively informative, thoroughly ‘kid friendly’ in organization and presentation, “Bristlecone: The Secret Life of the World’s Oldest Tree” by the team of author Alexandra Siy and illustrator Marlo Garnsworthy is an extraordinary, unique, and unreservedly recommended addition to family, elementary school, middle school, and community library Botanical Science picture book collections for young readers ages 8-10.”—Midwest Book Review

“The world’s oldest trees get the spotlight in Siy’s picture book. In her first book since Voyager’s Greatest Hits (2017), the author brings the story of a bristlecone pine tree to life. This nonfiction book’s story opens with a walk into the California mountains toward one of the world’s oldest trees. Readers learn how a bristlecone pine starts as a seed deposited on a rocky mountain, then stretches up toward the sky, developing growth rings. The pace is slow, soothingly moving through the seasons as the tree matures. Siy explains how scientists determine a tree’s age and possible threats to bristlecones that, if conquered, show up in its growth rings. It opens with life cycle and photosynthesis diagrams and ends with further details about bristlecones, a glossary, and a guide to animals in the book. This title conveys useful information that not only educates readers on bristlecones, but also offers wider lessons about dendrology in the vein of Christiane Dorion’s Into the Forest: Wander Through Our Woodland World( 2019).”—Kirkus Reviews

“Siy and Garnsworthy have created a picture book for all ages that is creative nonfiction at its best.  It spotlights STEAM, including an “A” for “art” plus science that shows us HOW we know while infusing a desire to WANT to know.  It innovatively includes suspense, romance, and wonder in a tale of these battle-scarred heroes of the plant kingdom.”—Vicki Cobb, Founder/President of iNK Think Tank, Inc.

“As beautifully illustrated as it is informative, this enchanting and engaging book takes readers on a journey through time. Through the lens of an ancient bristlecone pine’s lifecycle, the story of the world’s oldest trees blends science and secrets to draw readers into a surprisingly nuanced tale of history, biology, and ecological awareness that delights while it teaches.”—Dr. Matthew Salzer, Laboratory of Tree-Ring Research

“Featuring an informative yet approachable narrative and striking illustrations, the story of these aged plants is well told in this colorful book. The author also includes a nice summary at the end of the book, offering resource information for even deeper study of these truly amazing and long-lived trees.”—Children’s Literature

“Ancient bristlecone pines are the oldest trees on earth and have lived for more than 5,000 years. Within their rings are the secrets of the past. From volcanic eruptions and droughts to insect attacks and lightning strikes, each pattern of the rings tells us what the tree has experienced. These trees live in the harshest conditions and grow slowly across California, Nevada, and Utah. With “branches flexing, needles sunning, sugar surging, sap flowing, roots soaking—the seedling grows, ring by ring.” A beautifully told and illustrated story about the world’s oldest tree. Readers will also find a glossary of terms used in the book, a life cycle of the tree, and a field guide to some of the animals that live in the ancient bristlecone forest.”—KidsBookshelf

“In the White Mountains of California, behind White Mountain Peak, there lives ancient, twisty trees. The Ancient Bristlecone Pine Trees. In this informational picture book, Siy (author of, Mosquito Bite, Voyager’s Greatest Hits, and Cars On Mars), explains the life cycle of these ancient trees, one that is thought to be more than 5,000 years old. By examining their growth rings, these remarkable trees record different environmental conditions. ‘More moisture makes a wider ring. Drought slows growth so much that a ring may not form at all. Extreme cold damages woods as it grows, making a frost ring. Fire scars form when scorched wood is flooded with a sticky resin.’ The Ancient Bristlecone Pine Tree grows slowly. Fifty years, the tree is almost as tall as a crow. In three hundred years, it will be just three feet tall. The text draws readers in and clearly explains how the tree grows, repopulates, and how it survives in one of the harshest environments.  Paired with the engaging narrative are Garnsworthy’s meticulously researched illustrations. The pictures were created using watercolor, sand textures, and digital oil paint. They definitely bring the text to life.  Throughout the book some words that will appear in the glossary are in bold type. In addition to the glossary, there is a note with information about the Bristlecone Pine Trees.”—The Nonfiction Detectives

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Alexandra Siy

Alexandra Siy is the author of more than twenty notable books for children, including Mosquito Bite, Voyager’s Greatest Hits, and Cars on Mars, and the winner of many awards, including the American Institute of Physics Science Writing Award, the NSTA Best STEM Book award and an NCTE Orbis Pictus Honor. Alexandra shares her passion for science, photography, and books with students of all ages as a teacher and visiting author. She lives in Feura Bush, New York State. Please visit and


Marlo Garnsworthy

Marlo Garnsworthy is an Australian-American author, illustrator, editor, science communicator, and naturalist. Her published works include fiction and nonfiction, though nonfiction and science are her passion. She has traveled extensively, frequently accompanying scientists working in the field, and spent two months on a scientific research expedition, sailing on an icebreaker from Antarctica through the planet’s roughest seas, in the Southern Ocean. She lives in Wakefield, Rhode Island. You can learn more about Marlo, her books, and her school presentations at