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Among Trees, Oaks Are Giants for Many Reasons

Updated: Nov 1, 2023

Trees provide shade and shelter, and they are the homes of an untold number of living things. Across the world, millions of people depend on trees for their livelihood. And we can't forget that trees clean the air and help us breathe.

A white oak tree.
(Photo via Shutterstock)

Among trees, oak trees are particularly vital and important because they are a keystone species. These are species that other species in an ecosystem depend on. In the case of oak trees, they support more life — birds, mammals, insects, fungi and more — than any other kind of tree in North America.

The wood from oak trees has been sought after for centuries. In the era of wooden ships, the white oak and the English oak were the most sought-after trees for shipbuilding. So mighty is the oak tree that it was proclaimed the national tree of the United States in 2004. In addition, one species of oak, the white oak, was voted the state tree of Illinois in 1973 by schoolchildren from across the state.

It's not just recently that we've developed an appreciation for these trees. Oaks are steeped in history and legend too. Acorns, the fruit of the oak tree, were for centuries a food source for people across Asia, Europe, North Africa and North America. These massive trees have also been a symbol of endurance and strength for cultures dating back to ancient times.


Words to know

Bounty: Something given or occurring in generous amounts.

Endurance: To withstand a difficult process or situation.

Vital: Absolutely necessary or essential.


Today, the world is home to about 435 oak species growing on five continents. About 90 oak species are native to North America. They are among the longest-living trees in the world. White oaks, a common oak species, typically live more than 300 years. There's an English oak tree growing in Lithuania that is almost 2,000 years old, and there's a tree called the Jurupa Oak in California that has been alive for 13,000 years!

Our native oak trees can be divided into two groups: white oaks and red oaks. Common white oak species include the white oak, bur oak and chestnut oak, while common red oaks include the northern red oak, pin oak, black oak and scarlet oak. One of the primary differences between white oaks and red oaks is how frequently they drop their acorns. White oaks drop acorns every year, while red oaks drop acorns only every other year.

Oak trees have an easily identifiable leaf shape. The leaves are long with distinct lobes that have pointed or rounded ends. White oaks have rounded ends, and red oaks have pointed ends. But it’s the acorns that these trees are really known for.

It can take 20 or more years for an oak tree to begin to produce acorns. Once they do, they can produce quite a bounty. A single oak tree can produce thousands of acorns a year and more than 3 million over its lifetime. All those acorns don't yield new forests of oak trees, though. Only about one in 1,000 acorns will grow into a new oak tree.

All those acorns that never grow into new trees aren't wasted. Many wildlife species like to eat acorns. More than 100 animals native to the United States eat acorns, and they are considered one of the most valuable food resources for wildlife. Among the biggest fans of acorns are some of our most recognizable and respected animals — deer, chipmunks, opossums, raccoons, squirrels and birds such as blue jays, crows, quails, wild turkeys and wood ducks.

Blue jays' love for acorns helped spread oak trees far and wide following the last glacial period. In the fall and early winter, a white-tailed deer's diet can consist of more than 75% acorns as they try to bulk up for the coldest months. A bumper crop of acorns is even tied to an increase in deer birthing more twins the following year because their nutrition is improved.

Oak trees' leaves and even its sap also provide nutrition for wildlife, and the trees are also essential habitat for animals big and small. Caterpillars can be abundant in oak forests. More than 900 caterpillar species live in the oak forests across the United States. Compare that to another common and recognizable family of trees, the maples. Maple trees only attract 300 species of caterpillars.

Why are more caterpillars good? Because more caterpillars and more insects mean more birds and other wildlife, and that creates healthy forests and ecosystems.


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