Grow mimosa - Acacia dealbata

La Mimosa

The term mimosa commonly refers to a shrub belonging to the genus of acacias, in particular the acacia dealbata, whose small yellow flowers are usually given to women on the day of their feast.
The Mimosas are large shrubs, or even small trees, belonging to the genus of the fabaeae; are now widespread in the wild in most of the Italian peninsula and the Mediterranean, but have distant origins, in fact they are plants originating from Australia, from which they were imported in past centuries. The use of mimosa branches for Women's Day is simply due to the fact that these plants produce flowers in profusion towards the end of winter and it is therefore easy to get them on Women's Day, 8 March.
Those commonly known as mimosa flowers are actually spherical inflorescences, which bring together very small, very decorative, intensely scented canary-yellow flowers; the flowers are produced at the apex of the branches, on the thinnest twigs, and bloom in succession, starting from those closest to the stem. The flowering of the mimosa can last a few weeks and begins with the first days that are slightly long and not too cold, from January until March; in places with mild winters the mimosas produce flowers as early as the beginning of January, while in the cooler areas the flowering starts from the second half of February.
Acacia dealbata, popularly called mimosa, is a tree that, although not native, is now widespread in our country both in cultivation and as spontaneous, especially in areas with a mild climate. It is in fact fully a characterizing element of the Ligurian Riviera, of the shores of the great lakes and of all the coasts of our country. Although it has become a little invasive, it must be admitted that its cheerful and fragrant flowering reveals itself every year an inevitable symbol of the arrival of spring, giving vivacity to the landscape and awakening the first insect pollinators.
On the Riviera di Ponente it is also widely grown and harvested for horticultural purposes: its request increases exponentially on 8 March, Women's Day, to which it is inextricably linked.

Characteristics of the mimosa

The mimosa is native to Australia (which still considers it a national symbol). In particular the dealbacian acacia is endemic to the temperate and fertile Tasmania.
The subfamily of the Mimosaceae (belonging to the Leguminosae family) includes about 450 species of acacias mostly originating from the tropical and subtropical regions of Oceania, Asia, Africa and the American continent. They are mostly trees, but those that form beautiful bushes or have a climbing habit are not rare.
They came to Europe in the early nineteenth century and spread very quickly, given their adaptability and often vigorous growth (some can reach 8 meters in height in the first year of life!). They are however short-lived plants and are often irreparably damaged by anomalous frosts.
The acacia dealbata occurs mostly as a tree or shrub. It is characterized by a beautiful persistent foliage: the leaves are bipinnate, up to 12 cm long and formed by 15-20 elements, in turn divided into 30-50 silvery gray leaves, similar to feathers. The branches may be more or less spiny. The flowers appear at the end of winter (February-April): they are grouped into panicles comprising 10 to 200 flower heads of globose and soft shape, with yellow-golden or white, very perfumed stamens. The fruits are collected in pods that ripen from mid-summer to the end of spring.

Grow mimosa

This type of shrub needs a mild climate to be cultivated outdoors, as it fears frost, especially if prolonged and of high intensity; therefore in areas with very cold winters the mimosas are cultivated in pots or in a cold greenhouse. They still need a good fresh, well-drained but not stony or sandy soil; they prefer a good rich universal soil, mixed with organic fertilizer and small amounts of pumice stone, which guarantees the rapid flow of water.
It is a shrub that in nature easily reaches 4-5 meters in height, therefore in cultivating the mimosa let us remember to use large and capacious containers, and pruned regularly after flowering, to avoid excessive development.
They need regular and frequent watering, which keep the soil always slightly damp; therefore from March to October the waterings will be very frequent, and we will intensify the supply of water during the hottest months of the year. During the autumn and winter months, on the other hand, watering can be almost nil, although it is good to check the soil at the foot of the plant to prevent it from remaining dry for excessively long periods of time. The mimosas in fact fear the drought, so we will have to prevent the plant from remaining completely dry, especially during the warm months, but also in winter; we pay particular attention to specimens grown in pots, since the soil it contains can completely dry up in a very short period of time.

Special care

As mentioned before, to cultivate the mimosas, if necessary they are pruned after flowering, even if the specimens grown in the open ground are generally left to grow without pruning; as for the mimosas grown in pots instead an annual pruning is necessary, to avoid that with the passage of the time the shrub empties in the inferior part of the stem.
These plants are quite resistant to diseases, but sometimes they are attacked by aphids or mites; in general a vaporization of the foliage with water and soft soap may be sufficient to prevent the presence of parasites.
Remember to periodically enrich the soil in which we grow our mimosa; as for the plants placed in the ground every late winter we will spread at the foot of the mimosa some mature organic fertilizer, or even a slow release granular fertilizer, lightly hoeing the substrate. Instead to the mimosas grown in pots we can supply fertilizer for flowering plants, every 12-15 days, from March to October, mixed with the water of the waterings.

The real mimosas

Therefore the plants commonly called mimosas are actually specimens belonging to the genus of the acacias; but a genus called mimosa exists. Long ago also the acacia dealbata belonged to this genus, as well as many other plants; the in-depth study of plants at the cellular level has allowed classifiers to understand how the acacia dealbata belongs to the acacia genus, while some plants still belong to the mimosa genus.
On a visual level these plants have many common elements: for example both the acacia dealbata and the mimosas have pinnate foliage, consisting of almost needle-like leaflets; the gait is similar, although the mimosas have smaller dimensions. The mimosas also have flowers gathered in spherical inflorescences, but generally of a pink color.
Most plants belonging to the mimosa genus come from America; these are shrubs or small evergreen trees, characterized by a particular spring flowering, with light and delicate, quite aromatic foliage. Even the mimosas are quite rustic, but they fear intense and prolonged frosts.

Where to place the mimosa

The mimosa can be grown all over our country, even if in the harsh winter regions it is imperative to place it in large pots that can be moved to a sheltered room.
The choice of location is essential to obtain a vigorous and beautiful flowering specimen. The ideal is to insert it in a very warm and exposed area as much as possible in the sun, far from the winds. A wall to the south often provides it with the protection it needs, especially with regard to the winds that are frequent and frequently cause of extensive ramose desiccation.
We also avoid calcareous and poorly draining substrates that can damage the roots by creating stagnation.
They find use as isolated specimens, as elements of groves, but they can also become part of informal hedges. In this regard, however, we recall that it is a very competitive plant (in particular with respect to other mimosas) and therefore it is good to leave at least 3 meters between one specimen and another.
It should also be emphasized that the superficial roots are able to stretch for many meters and could damage foundations and plants. So let's remember to put them away from homes or set up strong barriers.

Plant in the open ground

Proceed in autumn (where the climate is particularly mild) or in spring. The specimens on sale are often grafted onto species with more tolerant roots.
We dig a hole that is not too deep and we firmly insert a brace of at least 5 cm in diameter. Then place the ground bread or the roots so that the grafting point is about 3-5 cm from the ground level. We buy, but avoid watering as the mimosa loves a dry soil. The fertilizations are equally superfluous because this plant, like the other leguminous plants, thanks to the symbiosis of the roots with some bacteria, is able to fix atmospheric nitrogen in the soil. In autumn, in any case, we prepare a thick vegetable mulch and cover the aerial part with special fabric.

In pot

We choose a rather large container, but above all a deep one. The ideal is to supply immediately one of at least 40 cm in height to then limit transfer operations as much as possible during the first few years.
On the bottom we create a draining layer with at least 5 cm of expanded clay.
The suitable substrate is made by mixing universal soil and peat in equal parts. A few handfuls of river sand can be a happy addition.
Let us irrigate slightly and try to keep the substratum always slightly damp, but never wet. The use of the saucer is absolutely to be avoided.


Mimosas want a substrate with a subacid and rather light reaction. If, on the contrary, our garden has an alkaline and heavy soil, we can choose to extract it and replace it completely with a purchased product (simulating the suggested mixture for the pots).
An excellent alternative is instead to obtain a specimen grafted on Acacia retinoides, (they are easily found in specialized nurseries) which is enormously more tolerant towards even very calcareous soils.
In any case, preparing a draining layer on the bottom will be of great help.


In the open ground irrigations are mostly superfluous. The need may arise only during long dry summers. We intervene only when we see a certain deterioration in the specimen.
In the pot it is proceeded with light administrations that always keep the soil cool, from spring to autumn, always avoiding stagnation. In the winter season, especially for the specimens collected inside, you can also suspend them altogether.

Exposure and climate

As already mentioned, the acacia dealbata is particularly heliophilous and thermophilic. It should therefore be placed in full sun and in a warm position. It fears cold winds and therefore the shelter of a wall to the south, especially in regions where the climate is not totally mild, can be of great help.
It does not tolerate temperatures below -5 ° C for a long time: therefore we carefully consider whether to place it in the open ground or limit ourselves to a cultivation in a container. Let us remember that the young specimens are the most sensitive and for which a prolonged frost can be really fatal.

Type of plant Tree, shrub or flowering creeper
Foliage Erected or groundcover
Flower color yellow
Height at maturity10 meters and more
Maintenance Low
Water needs Low
Ground Poor, pebbly
soil pH From subacid to acid (those grafted also tolerate basic soils)
RusticitŠ° From fragile to semirustic (at most -5 ° C)
Exposure Full sun
UseIsolated specimen, groups, hedges, vase

Protection from the cold

In the case of anomalous cold, small specimens can be used to cover with one or more layers of non-woven fabric. A further protection comes from a thick mulch with straw and foliage.
The mimosas in pots, in the North, must be sheltered in a cold, well-lit greenhouse, starting in November.
However it happens that the frost leads to drying up the entire aerial part: we wait patiently before explanting the specimen because it is not uncommon for it to create new sprouts from the roots.


Pruning should be done every year, to keep the tree compact and stimulate abundant flowering. We always proceed when the flower heads appear withered, generally around April. The branches must be shortened by about 1/3 and all those that are damaged or dead are eliminated, due to frost or other inconveniences. We also try to open the center by creating an inverted cone setting.
It is equally important to eliminate root suckers to keep the whole harmonious and prevent them from stealing energy from the main trunk.

Flowers collection

The collection period is the longest, as the production lasts for about 2 months. The individual panicles are collected with a little stem, accompanied by a few leaves.

Pests and diseases of the mimosa

Mimosas are attacked quite frequently by parasites.
The most common of all are the cochineals: in addition to weakening the tree they make it unsightly due to the honeydew and consequent smoke. Let's fight them with soft soaps for plants or possibly using mineral oil activated with systemic insecticides.
Another common problem is chlorosis: it is manifested by a general discoloration of the leaves, where the ribs will instead be evident. To overcome this it is good to replace the substrate with a more acidic one and to distribute iron sulphate often. Even a mulch made of bark and pine needles can help us. Let us remember to irrigate as much as possible with non-calcareous water.

Cultivating the mimosa: Mimosa propagation

The simplest method to obtain new plants is to extract one of the suckers from the soil, provided with a portion of roots.
However, it is also possible to proceed with sowing at the end of winter. The grains must be previously scratched with sandpaper (because they are very hard) and kept for at least one night in hot water: this will greatly speed up germination.
Those who are more experienced can also try grafting. For the root we prefer the acacia retinoides (also called semperflorens or Mimosa every month) which will make the subject tolerant even with respect to more clayey soils and will contribute to vigorous growth. The best time for this operation is from spring to the end of summer. The most common and most successful method is the graft by approximation.
Watch the video
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Flowering and harvesting February-April
PruningApril May
plant Autumn (Center-South), Spring (North)
graftFrom June to mid-September
SowingApril May
Home shelter and / or mulch Early November