Understanding Different Types of Trees

Learn About The Types of Trees Around the World

As you've probably guessed, we love trees and forests — and not just because of all of the incredible benefits they provide. With approximately 58,000 recorded and published species, trees represent an incredible wealth of genetic diversity and cover approximately 31% of Earth's land surface today. Even with the staggering deforestation that affects our global forests (the global forest area has declined by about 40% over the past 300 years), trees provide a home for at least half of the worlds terrestrial plant and animal species.  

Merriam-webster defines a tree as "a woody perennial plant having a single usually elongate main stem generally with few or no branches on its lower part". That captures the basics, but in reality, trees grow in a stunning variety of shapes, sizes and forms. Some grow tall and monolithic, with trunks so wide that several people could hug them at once without touching fingertips. Others are willowy and graceful, with elegant leaves and branching patterns that inspire the imagination.

No tree is exactly the same, just as no person is exactly the same — and that's part of why they have captured the human imagination for millennia. But what do we know about these majestic giants, beneath it all? 

The Two Primary Types of Trees: Gymnosperms and Angiosperms

In 1825, the Scottish botanist Robert Brown first distinguished gymnosperms from angiosperms. Angiosperms have seeds that are enclosed within an ovary, while gymnosperms have no flowers or fruits, and have unenclosed or “naked” seeds that sit on the surface of their scales or leaves.

Angiosperms

The majority of tree species today (and around 80% of all known green plants) are angiosperms — or deciduous trees. This means that they generally have: 

• Enclosed seeds
• Broad leaves that usually change color and die every fall.

Angiosperms include around 300,000 species of flowering plants and represent the largest and most diverse group in the plant kingdom. As vascular seed plants, they reproduce via the fertilization of an enclosed ovule that develops into a seed within a hollow, enclosed ovary (in contrast, the seeds of gymnosperms are usually exposed on the surface of their reproductive structures, like cones). They also have distinct male and female organs. Angiosperms occupy nearly every biome on Earth, but dominate terrestrial ecosystems.

They represent an incredible diversity of life that ranges from the tiny, 0.08 inch high watermeal plant to the massive 330 foot tall mountain ash tree in Australia — and are the main food source for birds and mammals. This diversity is a big part of why they've colonized more habitats than any other group of land plants.

Gymnosperms

The other main category of trees are gymnosperms, which predominantly includes types of evergreen trees like pine, juniperus, cedar, spruce and fir. This means that they typically have:

• Un-enclosed, or "naked" seeds
• Needles that stay green throughout the year (although some, like gingko and dawn redwood drop their leaves).

Gymnosperms were the first seed plants to evolve on Earth, and millions of years ago, during the Mesozoic Era, they were the dominant type of tree. But in the time since the Cretaceous Period, gymnosperms have slowly been displaced by angiosperms, which evolved more recently (if we can consider hundreds of millions of years ago "recent"). Today, gymnosperms are still successful in many parts of the world, with vast conifer forests dominating northern regions, like Russia and Canada.