What are the characteristics of the acacia tree?

Acacia saligna specimen

acacia saligna

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

If you would like to know more about him, 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.

Origin and characteristics of the acacia tree

Acacia caffra specimen

acacia caffra

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

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

Leaves

Acacia karroo seedlings

Seedlings of acacia karoo

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

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

They sprout from prickly or unarmed branches.

Flores

Acacia baileyana leaves

Leaves and flowers acacia baileyana

The flowers are grouped in racemose inflorescences. Each one of them looks like a miniature pompom, about 2-3cm in diameter, yellow in color. They are mostly hermaphrodites, but there are some who are unisexual.

Seeds

Acacia farnesiana seeds

Seeds of acacia farnesiana

The seeds are found in a dried 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 water at room temperature, and then sow them in a seedbed with black peat mixed with perlite, and in a matter of a week they will begin to germinate.

Branches and trunk

View of the trunk of the Acacia dealbata

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

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

Roots

The root system of acacias is very strong. Living in areas where rainfall is often low, its roots are not only able to penetrate well into the ground but also spread. For this reason, nothing should be planted near them. At a minimum, we have to leave a distance of 3 meters between the tree and any other plants that need regular fertilizers, and about 7 meters from any construction and pipes.

Main species of Acacia

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

acacia baileyana

Detail of the leaves and flowers of the Acacia baileyana

It is an evergreen shrub or 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-colored, greenish-gray or bluish. It is one of the first to bloom, as it does so in mid-winter. Resists up to -10ºC.

acacia dealbata

Acacia dealbata specimen in flower

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 glabrous upper surface and tomentose lower part. It blooms from mid-winter to early spring. Resists up to -10ºC.

acacia longifolia

Detail of the leaves and flowers of Acacia longifolia

It is one of the tallest 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 native to Australia. Its leaves are evergreen and long, up to 20cm long, dark green. It blooms in spring and resists up to -8ºC.

What care do they require?

Take care of your acacia so you can enjoy it for years

Acacia decurrens

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

  • Location: outside, in full sun. I insist, plant it as far away as you can from any construction and pipes to avoid problems in the future.
  • Land: not demanding. It grows well in poor soils, even those prone to erosion.
  • Irrigation: during the first year it needs at least one weekly watering, but from the second it is not necessary to water it.
  • Subscriber: It is not necessary. The only thing, if you dare to plant bromeliads or any other type of shade plant, you have to pay them regularly, otherwise the acacia will "steal" the nutrients.
  • Plagues 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 sow them in a pot with universal growing substrate. Cover them with a layer of soil so that they are not exposed directly to the sun, and keep them watered. Do not put too many in the same container, because when growing so fast it will be very difficult to separate them later. Ideally, put no more than 3 in a 10,5cm diameter pot.
    • Cuttings: in spring. You simply have to 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 perlite in equal parts. Keep it watered and in a place protected from direct sun, and after a month it will emit the first roots. Leave it in that pot for at least that year; so you can get stronger quickly.
  • Pruning: It's not necesary.
  • Rusticity: It depends on the species, but those that we can find in Spanish nurseries easily withstand frosts down to -10ºC.

Can you have a potted acacia?

Make your acacia a bonsai by following our advice

Acacia howitii
Image - Cbs.org.au

Well, I had several years a acacia salignabut she was barely growing and she didn't look pretty. It had a very thin trunk about 0,5cm thick and several branches that were too long. When planted in the ground, it only took two years for it to become strong. Its trunk quickly thickened, reaching a height of about 5cm, it gained height (3 meters) and many branches sprouted. Today it has been planted in the garden for about 6 years and it looks like a Weeping Willow 😉. Its crown measures almost 5 meters, and it takes both hands to hug the trunk (from the base).

So yes, you can have it in a pot for a few yearsBut sooner or later he will end up "asking" for a floor. Perhaps the one that lasts the longest is the acacia dealbata, or the acacia tortilis, because having very small leaves you can prune them and shape them as you want. Moreover, although it is not very common, there are those who are encouraged to work them as bonsai. The ones that I recommend you discard are all those that have whole and long leaves, since these tend to have a greater development that is not so easy to control.

The care is as follows:

  • Location: outside, in full sun.
  • Substratum: universal substrate for plants, even if you are going to work it as bonsai. Or if you prefer, mix 70% akadama with 30% kiryuzuna.
  • Irrigation: biweekly.
  • Subscriber: in spring and summer with liquid fertilizers. I advise to use guano, for its rapid effectiveness.
  • Transplant: every two years.
  • Pruning: late winter. You have to remove dry, diseased or weak branches, and trim all those that have grown excessively. The crown of the tree should be rounded or parasol.

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 to be able to enjoy them for many years, since otherwise problems would soon arise. I hope this article has helped you get to know these often misunderstood, but magnificent trees better.


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  1.   Antonio Madueno Aranda said

    Monica, good could you tell me where I can get seeds that are not invasive for a rainfed farm

    1.    Monica Sanchez said

      Hello Antonio.
      Acacia seeds can be found on ebay for example.
      All species have invasive roots, but perhaps the least is Acacia dealbata.
      A greeting.

    2.    SUSANA said

      Hello, I would like to know how many meters the roots reach; I have an invasion next to my house, I have a 5-year-old masonry wall and it fell back and my house also opened up; It is black acacia in my house I only have a 7-year-old Fresno .. Please if you can provide me with information .. Thank you

      1.    Monica Sanchez said

        Hi Susan.

        Ash roots are much more invasive than acacia roots, as they can extend horizontally ten meters or even more.

        But also those of the black acacia can cause problems, because although they are superficial they are quite strong. They do not reach ten meters, but it must be planted at least about 5 meters from the house.

        Greetings.

  2.   Mauro said

    Hello Monica, one of my acacias that I could not sprout and the tips are dry, but it is green downwards. What should I do to save her?

    1.    Monica Sanchez said

      Hello Mauro.
      I recommend watering it with rooting hormones that you will find in nurseries. Scoop a good handful around the trunk and water thoroughly.
      A greeting.

  3.   Rober said

    Because my mimosa acacia does not give flowers. It is more than 2 years old and is very grown

    1.    Monica Sanchez said

      Hi Rober.
      It may take a little more time. If you have it in the ground, surely within 1 or 2 years it will bloom. On the other hand, if you have it in a pot it can take you more.
      A greeting.

  4.   Laura Benavidez said

    Hello Goodnight.

    I have a question in January I planted an acacia tree of about 3 months and it was beautiful the first months but about 5 months ago the leaves began to fall and there is only one stick left, I checked it and it is not dry I have even seen how new twigs but I am concerned if it is not right, it is very important to know if it is normal or not that it is only a stick without leaves.
    Thank you very much.

    1.    Monica Sanchez said

      Hello Laura.
      How often do you water it? It is important to water it little, no more than 2-3 times a week in summer and every 6-7 days the rest of the year.
      If you are in the northern hemisphere now with autumn-winter it would be normal that until spring you would not see growth, so do not worry.
      A greeting.

  5.   Luis Garcia said

    Hello, I have an acasia tree ... big ... but many people who say they are experts have told me that it attracts many vichos. Like spiders and mosquitoes, is that so? What I can do

    1.    Monica Sanchez said

      Hi Luis.
      No, it does not attract many insects, only those that enjoy its flowers, such as bees, flies, wasps.
      A greeting.

  6.   Mirta sutinis said

    Very interesting, the information, I have one, from what you explain it is, acasia caffa.or something like that. He did not know. I want to buy another, but only for shade. It is ideal. And even if it's hot, it's cool down there! Thanks for the tips. - Mir

    1.    Monica Sanchez said

      Hi Mirta.
      If you have a large garden you can put an Acacia saligna, which gives very good shade. If not, an Acacia dealbata, which is smaller but very pretty too.
      A greeting.

  7.   Fabiola Hernandez said

    Hey.

    Thank you very much for the article, a question, I have a purple acacia of about 3 meters inside my house 2 months ago its leaves began to dry and fall, it began to sprout and its shoots are drying, every time I have to water it and I can put some compost, it is in a pot. Thanks a lot

    1.    Monica Sanchez said

      Hi Fabiola.
      If there are no strong frosts in your area, I recommend keeping it outside the home. Acacias are not well adapted to living indoors.
      There is watering 2 or 3 times a week in summer and every 4 or 5 days the rest of the year.
      A greeting.

      1.    Cinthya Spain said

        Fabiola, a question does the purple acacia give a lot of roots? I want to plant one in my outdoor garden but I have to break ground to place it on the side of a wall. Thank you. greetings my!

        1.    Monica Sanchez said

          Hi Cinthya.
          I think you have the wrong name 🙂

          I answer you, the author of the article. Acacias have strong roots, so it is advisable to plant them at a distance of 7 meters from pipes, soil, etc. On the contrary, you could put some citrus (orange, mandarin, etc.) for example.

          A greeting.

  8.   Roberto Pezet said

    hello I live in Houston, and I would like to buy an acacia dealbata (aromo) tree and I can't get it, they only offer seeds, I would like a tree, someone knows if it is possible to find it, thank you.

    1.    Monica Sanchez said

      Hello Roberto.
      I would recommend you look at online nurseries 🙂
      A greeting.

  9.   daniel said

    Every time I try to move an acacia tree dies.
    Example: I removed a small acacia from the ground without removing the roots into the air, that is, I also took the piece of earth that contained the roots, I made a hole the size of the piece of earth and planted it again, adding fertilized soil around and below .
    I watered it after flattening it and it dried right away.
    We are in summer at the moment, but in spring I also tried, with the same result.

    What am I doing wrong?

    Thank you

    1.    Monica Sanchez said

      Hello Daniel.
      I recommend doing it at the end of winter, before it resumes its growth (something you will see when you observe the buds, which will swell).

      Don't put compost under her, as it may be too much 'food' for her.

      For the first few times, water them with rooting hormones o homemade rooting agents.

      Regards!

  10.   salome siplis said

    My acacia bocha after 66 years dried up but from its roots children with thorns are sprouting, is that correct? Can I replant them? Will the thorns disappear? Thanks

    1.    Andrew said

      Hello. I wanted to know why acacias leak. it has a solution? Thank you.

      1.    Monica Sanchez said

        Hello Andres.

        Yes, we leave you this article in which we talk about the gum. It is not common in ornamental trees, but it does happen sometimes.

        Greetings.

  11.   Robert May said

    Excuse me, I want to plant acasia on my ranch, it is for a program, but my land is in Tabasco, Mexico, it will be that there is a humid tropic.

    1.    Monica Sanchez said

      Hello Roberto.

      Acacia grows best in hot and dry climates, so for your area I recommend more a jacaranda, or even a flamboyant if in your area there are never frosts.

      Regards!

  12.   Salt said

    Hi there! What things does the marijuana plant need? I would like to start using drugs but with natural things so that I can be healthy ... And if I can produce them, then all the better. So I don't need to go out to steal when I see myself lost in vice like my brothers.

    1.    Monica Sanchez said

      Hello Sun.

      Look from here! you will be able to see how is the cultivation and care of marijuana, as well as a link from which you can get products that may be useful to you.

      Regards!

  13.   Mirta said

    Hello, I have several acasia trees and some have a hole like it is black and a liquid comes out of it. Thank you.

    1.    Monica Sanchez said

      Hi Mirtha.

      From what you count, it seems that your trees have gum, caused by a fungus. In the link you have all the information about this disease.

      Greetings.

  14.   Iñigo said

    The article is very enlightening and instructive.
    But there is one thing I have in doubt; In my town there is a walk where there are some acacias (I think they are because of the characteristics mentioned above) and they have thorns on their branches. Is that so? Is it a feature?
    Thank you very much for the article and for your attention.

    1.    Monica Sanchez said

      Hello Iñigo.

      Although there are acacias that have thorns, such as acacia tortilis or the acacia cornigera, if you are in Spain it is possible that it is Gleditsia triacanthosthe Robinia pseudoacacia, since they resist the cold much better (the thorny acacias are tropical).

      Regards!