What is an Australian Mountain Ash Tree? - Home Stratosphere

What is an Australian Mountain Ash Tree?

Here is everything you need to know about the Australian Mountain Ash Tree, where they usually grow, what they look like, and how they are used.

This is a close look at a mature Australian mountain ash tree by the stream.

Curious about other types of trees? We’ve got you covered with 101 Types of Trees, and 11 Types of Eucalyptus Trees.

Related: Black Ash Tree | Red Flowering Gum Tree | Water Gum Tree | River Red Gum Tree

Eucalyptus Regnans

The mountain ash tree is an evergreen that is part of the genus eucalyptus that has over 700 eucalyptus species of flowering shrubs, trees, mallets, Marlocks, and mallees (we’ll expand on what those are in the Important Terms section).

Mountain ash trees are one of the most spectacular members of the myrtle family (Myrtaceae). They are called mountain ash or giant ash trees because of the resemblance of their wood to ash tree wood. They are also sometimes referred to as swamp gum (this is their name in Tasmania). Mountain ashes are native to Tasmania, Victoria, and Australia.

Mountain ash trees are the tallest living specimens on the planet. The tallest tree alive today is 100.5 meters. The tallest every on record was in 1872 before the trees were logged, and it lived in the Watts River region in Victoria at an absolute mind-boggling 132.6 meters. That is a tall tree, and that is a lot of biomass! Not even the coast redwood can compete with this monster.

Trees that big need a long time to grow, and these guys can usually exceed 500 years, as long as the growing conditions are right, there are no forest fires (which is never usually the case in that part of the world), and if they aren’t cut down. Either way, they are still a proud member of the old-growth forest.

One last really cool aspect of the mountain ash tree, before we get into the nitty-gritty, is the fact that eucalyptus forests can hold more carbon than any other forest on the planet. A study determined that groves that held trees over 250 years old, could store 2844 tonnes of carbon per hectare.

Important Terms for Eucalyptus Trees

This is a look at a forest of Australian mountain ash trees from the vantage of the pathway.

The eucalyptus genus contains many species and they are all very varying. There are different terms for these varieties based on the type of growth they have (if they are shrubs or trees, etc).

Mallet: mallets are a small form of tree around 10 meters tall. They are found in western Australia and the tree will have one single trunk, with branches that grow at a steep angle.

Mallee: mallees are a small form of tree around 10 meters tall. They are found in southeastern Australia and the trill will have multiple stems or multiple trunks, which branches that grow at a steep angle.

Marlock: marlocks are a shrub-like tree that is less than 5 meters tall. They are found in Australia and Tasmania, they grow one stem or trunk, and form a very dense canopy that grows very close to the ground.

Lignotuber: a lignotuber is a special adaptation that plants have in order to protect against fire damage. It is a bulbous woody swelling that occurs at the base of the trunk that grows partially above and partially below the soil. The lignotuber contains buds from which new stems can sprout if fire damage kills the body of the tree. It also contains starch that can feed the new seedlings in absence of their ability to photosynthesize.

What do Mountain Ash Trees Look Like?

This is a close look at an Australian Mountain Ash tree and its sign board on the side.

Root System

One of the most impressive features of the mountain ash tree is how quickly it can grow. This is entirely thanks to the development of the tree’s roots. A sapling will commence growth with a taproot system, which is few thick roots that grow very deep into the ground.

From there, lateral roots will start to sprout, and will usually extend far past the span on the crown. From the lateral roots, sinker roots will start to develop. Sinker roots grow very deep and vertically into the ground. Once a strong height is established, the taproot will die back.

This type of root system makes them nearly impossible to transplant, and they tend to interfere with surrounding plant life. However, it is understandable. How else is a tree that grows that quickly and that tall meant to do so?

Dimensions

Mountain ash trees are huge. The largest one alive today is 100.5 meters tall, though they will usually hover between heights of 60 and 80 meters, which is still an absolutely monstrous height. Such tall trunks require the width to support them, and they will usually be between 2 and 5 meters in diameter.

Growth Pattern

The mountain ash will have an extremely straight and upright trunk. Roots don’t start their growth until well up the trunk, with a small rounded crown that is rather open. Considering the enormous size of the trunk, the crown is awkwardly small and almost looks as if it doesn’t belong.

Foliage

Mountain ash trees are alternately arranged along the stems and leave lance curved-shaped (egg-shaped). A mountain ash leaf is glossy green and is 4-8 inches long. Both the upper surface and the lower surface of the leaf are covered with circularly shaped oil glands.

Bark

This tree will have smooth bark that is very light gray in younger trees and is only slighter darker in mature trees. It is very fibrous, flaky, and rough bark, and will peel off from the bottom and top in large stringy strips.

How do Mountain Ash Trees Reproduce?

This is a close look at the clusters of fruits of an Australian mountain ash tree.

Flowers

The mountain ash flower grows in clusters of 9-15. The flowers are hermaphroditic, meaning that flowers possess both female sexual characteristics, and male sexual characteristics. This does technically mean that they are able to self-pollinate, but the tree seems to understand the dangers of that.

Male sexual characteristics will mature before female sexual characteristics in order to prevent self-pollination. This is because self-pollination reduces the gene flow, and a tree that is a self-pollinated tree will have no adaptive traits and may be more vulnerable than a tree that has multiple genes.

Flowering occurs from the months of March to May, and the flowers are white. They grow on unbranched peduncles (branch specifically for flower clusters). Flowers are small, with white petals that are basically very thin filaments. The seeds are attached to the end of the filaments.

One mountain ash tree will produce over 1.5 million flowers in one season, which proves as a massive source of food for insects and animals. This is important for the reproduction of the tree.

Fruit

This is a close look at the clusters of fruits of an Australian mountain ash tree.

Once a tree has been either wind-pollinated or insect-pollinated, it will produce fruit in the form of a little seed called a gumnut. A seedling is pyramid-shaped and held firmly in place by a woody capsule.

The seeds will stay within their woody capsules in the tree for 3 years before they fall. Mountain ash trees have their reproduction methods completely adapted to fire threat. Once a seedling falls, it will remain ungerminated in the soil until a fire occurs.

This is because seedlings require very specific conditions in order to germinate. They need high levels of light, which they will only receive when the understory and overstory plants are taken out by a fire. They also need a mineral ash soil bed, which only occurs after a fire.

Sexual Maturity

The sexual maturity of a mountain ash tree is dependent on solar radiation and geographic location more than the age of the tree. If a tree receives more sun exposure it can start producing a productive seed crop as early as 7 years (which is very early considering how long these trees live) but it will more commonly occur around 11 years.

Lignotubers

Earlier we mentioned the function of a lignotuber. Though the mountain ash tree does not have a lignotuber, it is worth mentioning that other species of eucalyptus trees do. This is a brilliant way for the tree to ensure that its population does not get decimated from forest severe fires, which are common occurrences in Australia.

Many plant species have to adapt to fire damage, and the lignotuber makes it so that the forest can repopulate after the damage is done. Mountain ash trees can still repopulate after fires, but the downside is that they will only repopulate after a forest fire. So if that doesn’t occur for a long time, there will be no new trees.

Where do Mountain Ash Trees Grow?

This is a close look at a forest trail with Australian mountain ash trees.

Mountain ash trees are native to Australia and are present in every state and territory. Full three-quarters of the forests in Australia are actually eucalypt pure stands.

The highest elevation a mountain ash forest will occur is 1100 meters, and they prefer to grow in most cool, mountainous regions. Plantations occur all over Australia.

What are the Growing Conditions of Mountain Ash Trees?

Soil

Mountain ash trees prefer to grow in the soil of volcanic origin. These are usually friable clay loam soils.

Water Level

The most important condition for mountain ash trees is water level. They grow the best in regions that receive over 1000 millimeters of precipitation per year.

Sun Exposure

Mountain ash trees are sun-loving. They grow so tall so that they can access the largest amount of sun exposure. Their seedlings also need tons of sunlight in order to germinate.

How are Mountain Ash Trees Used?

A woman hiking through a forest trail with Australian mountain ash trees.

Wood

Mountain ash sapwood is a very light and attractive cream color. It is similar to ash wood, which is a highly valuable wood. The wood is easy to work with with a very straight grain and hardly any knots.

The wood is usually used for furniture, flooring, veneer, plywood, window framing, and paneling. It is a very important member of the timber industry, as it is the tallest hardwood tree on the planet!

Wildlife

Many bird species, like the yellow-tailed black cockatoo and possums, will usually the hollows found in old trees for their habitats. This large tree is very important for those on the forest floor and the rainforest understory.

Leadbeater’s (type of bat), possums, and yellow-bellied gliders will feed on the sap from the mountain ash tree. Koalas prefer harvesting on the foliage, and leaves are eaten by larvae of insects like the chrysomelid leaf beetle, the long-horned borer, eucalyptus weevils, and the tortoise beetle.

FAQs

Are mountain ash tree roots invasive?

One of the most impressive features of the mountain ash tree is how quickly it can grow. This is entirely thanks to the development of the roots of the tree. A sapling will commence growth with a taproot system, which is few thick roots that grow very deep into the ground.

From there, lateral roots will start to sprout, and will usually extend far past the span on the crown. From the lateral roots, sinker roots will start to develop. Sinker roots grow very deep and vertically into the ground. Once a strong height is established, the taproot will die back.

This type of root system makes them nearly impossible to transplant, and they tend to interfere with surrounding plant life. However, it is understandable. How else is a tree that grows that quickly and that tall meant to do so?

Are mountain ash trees messy?

Because mountain ash trees are evergreen, they aren’t particularly messy. Though their bark does exfoliate and they will drop their flowers in late autumn, eucalyptus trees aren’t known for being messy.

Are mountain ash trees fast-growing?

Mountain ash trees are wildly fast-growing. They are known for their impressively fast growth. They will grow upwards of 2 meters per year for the first 20 years of their life, and that speed will eventually slow afterward.

Are mountain ash trees evergreen?

Mountain ash trees are evergreens. This means that they do not shed their leaves seasonally. Trees that are evergreens are able to obtain all of the nutrients and energy they need all year round and do not have to go into dormancy in the winter months.

Do mountain ash trees have thorns?

Mountain ash trees do not have thorns.

When do mountain ash trees bloom?

Mountain ash tree flowers usually bloom in the months of March to May. The leaves will stay on the trees for a couple of months to ensure pollination.

How long do mountain ash trees live?

Trees that big need a long time to grow, and mountain ash trees can usually exceed 500 years, as long as the growing conditions are right, there are no forest fires (which is never usually the case in that part of the world), and if they aren’t cut down. Either way, they are still a proud member of the old-growth community.

A more average life expectancy for the mountain ash tree is over 250 years.

What is another name for the mountain ash tree?

Mountain ash trees have the scientific name eucalyptus regnans, and it goes by a couple of nicknames as well. They are called mountain ash trees because of the resemblance their wood has to that of the ash tree.

They are referred to as swamp gum trees in Tasmania, because of the areas in which they grow. They are also sometimes called stringy gum trees because of the way that their fibrous bark defoliates in a stringy panel-like way.

Do eucalyptus trees have deep roots?

One of the most impressive features of the mountain ash tree is how quickly it can grow. This is entirely thanks to the development of the roots of the tree. A sapling will commence growth with a taproot system, which is few thick roots that grow very deep into the ground.

From there, lateral roots will start to sprout, and will usually extend far past the span on the crown. From the lateral roots, sinker roots will start to develop. Sinker roots grow very deep and vertically into the ground. Once a strong height is established, the taproot will die back.

This type of root system makes them nearly impossible to transplant, and they tend to interfere with surrounding plant life. However, it is understandable. How else is a tree that grows that quickly and that tall meant to do so?

Is eucalyptus a gum tree?

Some species in the eucalyptus tree family are referred to as gum trees because they copious kino from their bark if there is a large break. This is similar to the sap. But not every member of the eucalyptus genus is a gum tree.

What is the tallest flowering plant?

The tallest flowering tree (angiosperm) on the planet is the mountain ash tree that is in the eucalyptus family. The tallest specimen alive right now is 100.5 meters tall. The tallest one known in history grew to 132.6 meters in the Watts River region of southern Victoria!

Are mountain ash trees a fire-sensitive species?

Mountain ash trees aren’t a fire-sensitive species, because they live in a region where plant life can only survive if it is able to adapt to fire. Though they do not have a lignotuber;

a lignotuber is a special adaptation that plants have in order to protect against fire damage. It is a bulbous woody swelling that occurs at the base of the trunk that grows partially above and partially below the soil. The lignotuber contains buds from which new stems can sprout if fire damage kills the body of the tree. It also contains starch that can feed the new seedlings in absence of their ability to photosynthesize.

But the way in which they reproduce makes it so that their population is never completely wiped out from a forest fire because their seedlings can only germinate in mineral ash soil.

What is the difference between a swamp gum and a rose gum tree?

Swamp gum (eucalyptus regnans) and rose gum (Eucalyptus Grandis) are part of the same family, though their growing regions are quite different. The swamp gum occurs all over Australia, whereas the rose gum can only be found in southeastern Australia along the coast.

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