Acacia Tree

Acacia Tree

When you have a piece of land and you want to create a garden with fast growing plants that give very good shade, itis very interesting to choose to plant an acacia tree . If the conditions are right, it can grow at a rate of half a year, and it is not necessary to water it too often because it resists drought.

If you would like to know more about it, I will tell you what are the characteristics of the acacia tree so you can identify it every time you go to a nursery or visit a garden. In this way, you can get ideas on how to design yours with this beautiful tree.


Characteristics Of Acacia Tree

Acacia is a genus of trees and shrubs that belong to the botanical family Fabaceae, subfamily Mimosoideae. There are about 1400 accepted species , although there are more than 3000 described throughout the world. It is, by far, one of the most widespread. It can be found in tropical and subtropical regions around the planet, especially in Africa and Australia. In the case of Spain, the Acacia dealbata are very popular, being found even feral in some points, and the Acacia saligna.


Their height depends on the species, but they tend to grow from 5 to 10 meters. Let’s see in detail what its parts are:


The leaves can be perennial or deciduous , depending on the climate in the area. Thus, those species that live in places where it does not rain at any time of the year and are also very hot, will drop the leaves to survive, as is the case of A. tortilis for example; On the other hand, those that live in places where they can have water and do not have problems with the heat or the cold, will be producing new ones throughout the growing season.

If we talk about size, in the vast majority of species are small, no more than ten centimeters in length, but there is some, such as Acacia saligna , which produces up to 20cm in length. They can be lanceolate or paripinnate , that is, they are composed of very small leaflets. The colors vary, being light green to dark green.

They sprout from thorny or unarmed branches.



The flowers are grouped into racemose inflorescences, as a raceme . Each of them looks like a miniature pompom, about 2-3cm in diameter, yellow in color. They are mostly hermaphrodites, but they have to be unisexual.



The seeds are found in a dry fruit that can be flattened or sub-cylindrical . They are found in large numbers (minimum 10) and germinate fairly quickly. In fact, you only have to subject them to thermal shock, that is, put them in boiling water for a second and 24 hours in room temperature water, and then plant them in a nursery with black peat mixed with pearlite, and in a matter of a week they will begin to germinate.

Acacia farnesiana SEEDS

Branches and trunk

The wood of this tree is quite hard. The trunk , although it grows very fast (some species are able to grow at a rate of 70cm per year), by keeping well anchored in the ground is one of the strongest and most resistant of all fast-growing trees . It is, therefore, a highly recommended plant to have in gardens where the wind blows regularly.

Likewise, the branches after a few years remain flexible but they are not the ones that break easily . In fact, wood is used to build furniture of all kinds: tables, chairs, stools …

TRUNK OF AN Acacia_farnesiana

Root System

The root system of the acacias is very strong . When living in areas where rainfall is often scarce, its roots are not only able to penetrate well into the soil but also extend. For this reason, nothing should be planted near them. As a minimum, we have to leave a distance of 3 meters between the tree and any other plant that needs regular fertilizers, and about 7 meters of any construction and pipes.

Main species of Acacia

We show you the three main species of this incredible genre:

Acacia baileyana

It is a shrub or evergreen tree native to Australia that reaches a height of between 3 and 10 meters known as mimosa or common mimosa. Its leaves are bipinnate, ash-gray greenish or bluish in color. It is one of the first to bloom, as it does in mid-winter. Resists until -10ºC.

Acacia dealbata

It is an evergreen tree native to Australia and Tasmania that reaches a height of between 10 and 12 meters. Its leaves are bipinnate and are formed by up to 40 pairs of leaflets with the glabrous beam and the underside of the tomentose. It flowers from mid winter to early spring. Resists until -10ºC.


Acacia longifolia

It is one of the highest species: it can grow up to 11 meters. It is known as Acacia trinervis, Double Aroma, Golden Mimosa, Golden Wattle, Sallow Wattle and Sydney Golden Wattle, and is originally from Australia. Its leaves are perennial and long, up to 20cm in length, dark green. It blooms in spring and it resists until -8ºC.


What care do you require?

If you would like to have an acacia in your garden, write down these tips:

  • Location : outside, in full sun. I insist, plant it as far as you can from any construction and pipes to avoid problems in the future.
  • Soil : it is not demanding. It grows well in poor soils, even in those that have a tendency to erosion.
  • Irrigation : during the first year you need at least one weekly irrigation, but from the second it is not necessary to water it.
  • Subscriber : it is not necessary. The only thing, if you decide to plant bromeliads or any other shade plant, you have to pay them regularly because otherwise the acacia them “steal” nutrients.
  • Pests and diseases : they are very resistant.
  • Transplant : in spring.
  • Multiplication :
    • Seeds: in spring. After the thermal shock that we explained before (having them 1 second in boiling water and 24 hours in water at room temperature), you have to plant them in a pot with universal growing medium. Cover them with a layer of earth so they are not directly exposed to the sun, and keep them watered. Do not put too many in the same container, because when you grow so fast it will be very difficult to separate them later. Ideally, do not put more than 3 in a pot of 10.5 cm in diameter.
    • Cuttings: in spring. Simply cut a piece of branch that measures at least 40cm, impregnate the base with rooting hormones and plant it in a pot with universal substrate mixed with pearlite in equal parts. Keep it watered and in a place protected from the direct sun, and after a month it will emit the first roots. Leave it in that pot at least during that year; so it can be strengthened quickly.
  • Pruning : it is not necessary.
  • Rust : depends on the species, but those found in Spanish nurseries easily withstand frost of up to -10ºC.

Can you have a potted acacia?

Well, I had an Acacia saligna for several years , but it hardly grew and it did not look pretty. It had a very thin trunk about 0.5cm thick and several branches too long. By planting it on the ground, it took only two years to strengthen. His trunk swelled quickly, reaching about 5cm, took height (3 meters) and sprout many branches. Today it has been planted in the garden for about 6 years and it looks like a weeping willow ????. Its cup measures almost 5 meters, and both hands are needed to embrace the trunk (from the base).

So yes, you can have it in a pot for some years , but sooner or later you will end up “asking” for soil. Perhaps the one that lasts longer is the Acacia dealbata , or the Acacia tortilis , because by having very small leaves you can prune them and form them as you want. Moreover, although it is not very common, some people are encouraged to work them as bonsai. The ones that I recommend discarding are all those that have the whole and long leaves, since these tend to have a greater development that is not so easy to control.

The cares are the following:

  • Location : outside, in full sun.
  • Substrate : universal substrate for plants, even if you’re going to work as bonsai. Or if you prefer, mix 70% akadama with 30% Kiryuuzuna.
  • Watering : twice a week.
  • Subscriber : in spring and summer with liquid fertilizers. I advise using guano , for its quick effectiveness.
  • Transplant : every two years.
  • Pruning : late winter. You have to remove the dry, diseased or weak branches, and cut out all those that have grown excessively. The crown of the tree should be rounded or folded.

Acacias are very fast growing trees that look great in gardens. But, as we have seen, it is very important to take into account some things in order to enjoy them for many years, otherwise the problems would soon arise. I hope this article has helped you to get to know these, often misunderstood, but magnificent trees.Do you know what



The genus Acacia belongs to the family of legumes (Fabaceae) and is classified in the subfamily Mimosoideae. This plant genus, which is native to Australia, comprises almost 1,000 species. Of the non-hardy plants, some species are popular as house plants in this country. Note: Acacias are often confused with Robinias (Robinia pseudoacacia) because of their similar appearance. Therefore Robinias also bear the name “false acacia”. However, the two plant genera are not closely related. Genuine acacia trees are also often called “mimosa trees” have little to do with the real mimosa (Mimosa pudica)

Appearance and growth

Acacias usually grow as evergreen shrubs, less often than trees. They grow between 5 and 15 metres high. In the tub, however, they usually only reach heights of around two metres. Their branches are spiny in some species, the foliage is mostly pinnate. The tannin-rich bark of acacias is brown and cracked. Many species have honey- to lemon-yellow spike-like or cluster-like inflorescences with a bewitching scent. They attract bees in droves to collect nectar in their homeland. The flower pile appears from midwinter to early spring.

Location and substrate

Since acacias like it to be very bright, sunny and warm, the potted plants spend the summer best outside on the terrace – preferably in full sun. If you have a suitable place in the garden, you can also place the acacia in a bed together with the pot in the summer. In their Australian homeland, acacias are found in steppe landscapes and sandy soil. Therefore, place acacias in fresh, moist potted soil, which you have loosened up with expanded clay, gravel, perlite or sand, so that the substrate becomes loose and permeable


Since acacias form a broad crown, you should choose the largest possible pot for planting. Ensure that there is sufficient water drainage in the bottom of the pot and do not place acacias on coasters! Before planting, the root ball of the acacia should be placed in a bucket of water until no more air bubbles rise. Fill a layer of drainage into the pot, cover it with a planting mat and place the potting soil on top. Insert the wet root ball, press firmly and fill with soil to just below the edge of the pot. Even after planting, the acacia should be well watered again.

Care tips

Real acacias do not place high demands on care. The plants cover their own nitrogen requirements via nodule bacteria in the root area. Nevertheless, it is advisable to add some liquid fertilizer to the watering water of the densely foliated, richly flowering trees every 14 days. Although acacias can tolerate drought for a while, they are very thirsty due to their leaf mass and should therefore always be watered with rainwater that is low in lime. In order to keep the fast-growing crowns in shape and to prevent them from balding, they should be cut back slightly after flowering. Caution: Do not cut acacias in autumn, otherwise the next flower will fail


Acacias that are not winter-hardy are best kept in a cool and bright conservatory where the temperature does not fall below five to ten degrees. There, too, watering should be done regularly but in a reduced way, as the plant is in the dormant phase. Fertilizer application should now be stopped. Caution: If the acacia hibernates in the dark, it will shed its leaves. When clearing out the plant in spring, get it slowly accustomed to the sun, otherwise it will quickly catch sunburn.

Important species and varieties

The golden acacia (Acacia pycnantha) – not to be confused with the golden robinia (Robinia pseudoacacia ‘Frisia’) – grows in the tub as a small tree about two metres high and lives up to its name with its lush flowers. It is the national plant of Australia. The mimosa of the four seasons or ever-flowering acacia (Acacia retinodes) is a large shrub that can grow up to five metres high. Acacia retinodes blooms in the conservatory all year round with golden yellow flower panicles. Plenty of water and sunshine cause the densely bushy kangaroo thorn (Acacia armata) to bloom outside in the garden in the spring months. The angular, thorny branches tolerate regular pruning very well. Sun-yellow cascades of fluffy flower pompons decorate the willow-like branches of the willow-leaf acacia (Acacia saligna) every spring over a length of more than 50 centimetres. The richly flowering silver acacia (Acacia dealbata) or false mimosa is best suited for bright, unheated conservatories. Its finely feathered leaves have a silvery shimmer. Already at the beginning of March its yellow flowers ring in the spring.


Most acacias can be propagated by cuttings. To do this, cut head cuttings about 15 centimetres long from the mother plant, remove the lower leaves, dip the cut in rooting powder and place the branches in a bowl of growing earth. For good rooting, two thirds of the branches should be stuck in the soil. Cover the cuttings with a plastic cover or cling film. When the first new leaves appear, the cuttings can be put into pots

Diseases and pests

When acacias shed their leaves, they are too dry, too wet and/or too dark. A yellow colouring of the leaves indicates too much lime in the watering water. In the winter quarters you should check for wool and scale infestation from time to time.

Don Burke

I am Don Burke, one of the authors at My Garden Guide.  I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.

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