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Tree Fern Structure

By Bonnie Grant ; Updated September 21, 2017
Tree ferns are large ferns borne on trunk-like stems

Tree ferns are not trees but ferns in the order Cyatheales. They are found in many parts of the world, but primarily humid tropical forests. Varieties of tree ferns include Tasmanian, Australian, soft fern, hardy tree fern and man fern. There are even tree ferns native to the Pacific Northwest. The plants are characterized by a long trunk-like stem which carries the fronds high above. Approximately 800 species of tree fern exist. Semi-hardy to U.S. Department of Agriculture plant hardiness zone 8, these ferns are slow-growing, statuesque beauties.

The Trunk

The trunk is composed of much different material than a tree trunk. It is made up of fibrous roots and is called the "caudex." The trunk does not increase in diameter like a tree trunk, but rather grows in height. The appearance of the trunk is woolly and fuzzy due to the texture of the roots.The trunk will not appear until the fern is around three years old and then it will grow at a rate of at least 2 inches per year until maturity


Tree ferns can grow up to 30 feet high depending upon species..Tree ferns do not produce fruit or seed like most plants use to propagate themselves. Instead, the underside of the leaves will be covered with spores. These are the fruiting bodies and reproductive structures of the plant. The wind and animals movements will disperse the spores, but few find a hospitable place to grow.The leaves emerge as "croziers," the classic curled baby fronds.

The Crown

The trunk is topped by a fan of large fronds, each of which can be up to 6 feet long. The effect is a feathery umbrella of immense size and lush green foliage. Croziers unfurl from the crown and spread outward. The crown is situated atop the "trunk".


Tree ferns form from rhizomes. The rhizome actually forms the trunk as part of the root structure. In the case of tree ferns, the rhizome is simply very long and strong enough to support itself, according to Ian Barclay of The Desert Northwest Nursery, Sequim, Washington. The rhizome is a transport for nutrition to the "trunk" and then up to the crown.


Most species of tree fern are considered threatened and it is illegal to transport or ship the plants or their products to other countries. This is because the habitat of most tree ferns is tropical forest which is a rapidly diminishing ecosystem.


About the Author


Bonnie Grant began writing professionally in 1990. She has been published on various websites, specializing in garden-related instructional articles. Grant recently earned a Bachelor of Arts in business management with a hospitality focus from South Seattle Community College.