Silver Wattle / Acacia
(Acacia dealbata)
Country of Origin : Australia
Bonsai Styles : Informal upright, Slanting, broom, clump, group, cascade
Zone : 7 – 11
Acacia dealbata tree is native to tropical and sub-tropical regions (can not tolerate frost). Acacia Dealbata is an evergreen tree.
It is also known as Silver wattle and Mimosa. However it should not be confused with Albizia julibrissin, which is also known as mimosa tree.
Known for its pinnate leaves and small, delicate foliage, it is often used by florist.
It makes for a great indoor bonsai tree.
In the course of time, the bark becomes deeply furrowed and turns from gray to light brown in color. However the tree forms a rough textured bark relatively fast.
These trees have compound leaves. Leaflets of the tree are feathery and finely divided, with a soft, medium green color.
It has slightly rough, well-branched stems that are a rich chocolate brown or gray. Some of the species of acacia have cluster of long sharp thorns.
Some of the other Acacia species which can be used to make bonsai are :
Acacia spectabilis, Acacia verticillata, Acacia karroo, Acacia cavenia, Acacia baileyana and Acacia farnesiana
Out of these species, A. farnesiana and A. baileyana are prefered more to make bonsai. (mainly for their tendency to remain small even in the wild).
Acacia baileyana requires a cool indoor temperature of 46°F to 53°F (8°C to 12°C) during the winter, while Acacia farnesiana can tolerate warmer temperatures.
Read more about other bonsai trees species in : Types of bonsai tree
Generally, acacias are able to bear golden puff-like, very fragrant flowers that are followed by legume pods, but getting acacias to flower in bonsai culture is reputed to be challenging.
The flowers bloom in clusters after late winter, then sporadically after new growth, so they are nearly always in bloom.
Leaves of Acacia tree.
Best location to keep acacia Bonsai
Acacia dealbata can be kept in full sun and partial shade. However, this plant tends to close its leaves, when it has had enough of sunlight. Hence, it can be placed in partial shade all the time. And this quality makes it a great choice for making an indoor bonsai tree.
A good temperature range to grow this bonsai is 68°F-82°F (20°C-28°C).
This tree (when planted on land) has been observed to tolerate temperature as low as 23°F (-5°C) for brief period. However, when grown in containers, move it to a protected shed or indoors when the temperature goes so low.
A good winter temperature for Acacia dealbata bonsai can be 41° F – 52° F (5° C -11° C).
Keep it in or near a window (west, south or east) when growing it indoors. Maintain good air circulation.
IMP: Refer sunlight requirements for indoor plants for more indoor gardening ideas. Also, refer to do bonsai trees need sunlight for more indoor and outdoor bonsai location ideas.
Propagation of acacia
Acacia can be propagated by using seeds or semi hard wood cuttings in summer.
When showing seeds, first subject the seeds to thermal shock. (Subjecting the seeds to 230°F (110°C))
Put the seed in boiling water for 10 minutes. And then once the swollen seeds have cooled down, sow them in the growing medium.
When using stem cutting, rooting hormone and bottom heat will promote rooting.
Watering acacia Bonsai
The water requirements for acacia are only moderate, and while it should be kept moist, do not soak it for long periods of time.
Keep watering down during the winter unless you’re in a warm environment.
It is good to spray some mist occasionally on the bonsai , but this is not necessary.
Read watering bonsai tree for more details.
Wiring acacia Bonsai
These trees are very easy to wire. Branches take shape relatively fast. Be careful of the thrones or you can even prune them if you don’t want them.
Wire training can be done after the flowering is over (if you manage to get them on your acacia bonsai tree) and the tree is still in active growth. Or wiring can also be performed when the tree is completely defoliated. Do the defoliation in late spring. This season will give you more time to keep the wires on the tree.
Remember, that the older branches are quiet brittle, so take due care. The younger branches are flexible and can be wired easily.
Make sure that you do not damage the bark of the tree while wiring as its one of the main attractions of the bonsai.
Use guy wire if you can. You can also use copper wires, however, wrap some raffia around the branches to protect the flaky bark.
Even if you managed to leave a mark on the bark, as the bark ages, it will hide the mark.
Pruning acacia Bonsai
When to prune acacia bonsai?
How to prune acacia bonsai?
Acacia are fast growers. Hence, regular pruning is required.
Regular pruning is also required for the fact that, the growth habit of Acacias tends to be toward the top and lower branches sometimes die back as a result of this tendency.
If you are lucky enough to have flowers on your trees, the main pruning should be done after the flowers have finished blooming.
Usually, this occurs at the end of the winter or at the beginning of spring.
Pruning of main branches can be carried out at any time of the year, regardless of the season.
When ever you are performing pruning, leaves a sizable amount of stub. And, do not remove the bud which you wish to develop into a branch.
The stub will most likely die. You can remove this stub later (when it has dried).
It is essential to apply cut paste on the pruning wounds. It will prevent infection and also limit the die back.
There is no point in pruning the leaves of Acacias, since they have compound leaves.
Repotting acacia Bonsai
When to repot acacia bonsai?
Repotting of acacia bonsai tree can be done every 2-4 years. This also depends on how mature the tree is. (younger 2 years and older 4 years)
In case you are also planning to prune the root, keep 2 things in mind. First, the tree should be relatively cool and second, do a light root prune.
Also keep in mind that root system of this tree does not seem to be very strong. Do not remove the nodules. These nodules are essential in absorbing nitrogen for the tree.
Choose a deep bonsai pot since this tree doesn’t have a strong root system.
You can use a basic free-draining bonsai soil mix as a potting soil. Can be grown in acidic or alkaline soil.
Must Read: Bonsai Soil Recipes
Must read : Choosing the right bonsai container
Feeding acacia Bonsai
In the growing season, it is recommended that you feed your acacia bonsai every three to four weeks, using a general purpose feed that has a fairly low nitrogen content. High nitrogen will promote long inter-nodes.
In the winter, provided that the plant is placed in a cool place (41-52°F), you can skip feeding the tree.
Read more about bonsai fertilizer and its application.
Diseases and pest of acacia Bonsai
These trees are usually pest free. However, if not taken care of, these trees can be attacked by Red spider mite, scales and aphids.
Use a systemic insecticide. Or keep the bonsai in good light and air conditions to avoid such issues all together.
Acacia bonsai care
Sometimes over watering will cause the acacia dealbata bonsai to “bleed” from the trunks. This is normal, its called gummosis. This is a natural tendency of the plant to release excess pressure from the trunk and the stems and prevent them from bursting.
Wipe this sap from the trunk or else it will leave a mark on the trunk.
The shedding of leaves also is a sign on less watering. Water the plant in case you notice this with your acacia bonsai.
The promote formation of small twigs and also to achieve growth of smaller sized leaves, you can do defoliation of the bonsai tree.
