Eucalyptus regnans
Australia has the tallest trees in the Southern Hemisphere, including many species of Eucalyptus over 200 feet and at least one over 300 feet. Known as mountain ash in Victoria and swamp gum in Tasmania, Eucalyptus regnans is the undisputed tallest flowering plant in the world. Rumors of its extraordinary height abound, and there have been well-publicized claims of several trees over 400 feet that were either logged or burned in the 19th and 20th centuries. The highest credible report is of a 375-foot-tall tree felled near the Victorian town of Thorpdale. Today the tallest living individual is a Tasmanian tree 318.2 feet to a dead top. The highest known leaf is on a 303-foot-tall live-topped tree in Victoria’s Kinglake National Park not far from the town of Whittlesea. Here are several photographs of these amazing trees, which I have been studying since 2002.
Eucalyptus regnans is a flowering plant of the Myrtaceae. It has small white flowers produced from buds on a pedicel.
Climbing Eucalyptus regnans can be intimidating, because the trees are very open with little to obscure one’s view of the ground. Here Bob Van Pelt (red helmet), Jim Spickler (orange helmet), and Marie Antoine get ready to map the crown of a 303–foot–tall tree.
The tallest forest in the Southern Hemisphere is an awfully windy place. Cold air masses from the Antarctic Ocean vie with warm air masses from the continent’s interior to create ferocious winds that these trees ride throughout their lives. Here is a view of the highest known Eucalyptus leaves being tossed about by strong winds on a typical day.
The tallest tree on the Australian mainland towers above the forest with a strident, wind–defying crown. Here is a view of this 303–foot–tall tree from near the top of a 281–foot–tall tree. A sulfur–crested cockatoo is sitting on a branch near the top.
Trunks of Eucalyptus regnans soar above a dense understory of tree ferns and flowering shrubs that extends to only about 50 feet. All of the Eucalyptus trees visible in this 2006 photograph are thought to be within one month of 297 years old, having established after a catastrophic fire
Climbing above the understory reveals breathtaking views of what seems like an infinity of Eucalyptus trunks extending in all directions. In this view of a 297–year–old forest, a few Acacia trees rise above the understory to about 80 feet.
Tree ferns dominate much of the understory in tall Eucalyptus regnans forests. Here is a view looking down on a dense grove of tree ferns and flowering shrubs during late spring.
Each year Eucalyptus regnans loses its outer layer of bark, which falls off in long strips. On this foggy morning, rivulets of water were flowing down the smooth bark, creating slippery conditions for climbing.
Eucalyptus regnans is one of the world’s fastest growing species. For example, we know of a 67–year–old tree that is over 269 feet tall. The tallest trees in this 297–year–old forest are still growing in height by almost 11 inches per year.
The incredibly fast growth rate of Eucalyptus regnans comes at a price. These trees have low resistance to wood decay fungi, in part because they invest so little energy to chemically protect their heartwood. Nearly every tree in this 297–year–old forest is hollow and beginning to fall apart.
Peeling bark prevents epiphytes from colonizing Eucalyptus regnans, but some parasitic plants flourish in their crowns. Here is a flowering mistletoe 201 feet high in a 234–foot–tall tree. Note that its leaves are similar in shape to those of its host.
A dazzling array of arboreal animals inhabits Eucalyptus regnans. This bright red caterpillar cruised past while we were measuring photosynthesis near the top of a 300–foot–tall tree.
There are lots of poisonous creatures in Australia, and some of these inhabit the forest canopy. I startled this impressive centipede from beneath a peel of bark while climbing one day, and I felt lucky when it ran away.
Some big spiders dwell in the crowns of Eucalyptus regnans, and so one must be extra alert while climbing. This large–fanged huntsman was a constant worry to my wife Marie, whose shrill cries alerted us the instant she encountered one.
