Mimosa - Acacia dealbata


The mimosa (acacia dealbata) is a tree native to Tasmania, but which, having arrived in our country in the mid-1800s, has adapted very well to the climate of the Ligurian Riviera and that of the southern regions and the great lakes: it has even entered part of the landscape of these places thanks to the irrepressible flowering which, among the earliest, announces the arrival of spring.
Mimosa is native to the Australian continent. In Italy they resist well in the temperate climates of central and southern Italy, but they can also be cultivated on the coasts of the great northern lakes, where they can benefit from milder temperatures. Cultivation in other areas must be carried out in pots or in greenhouses.
There mimosa plant it can even reach considerable sizes. The leaves are composed of many leaflets placed perpendicularly to the main rib. Some varieties do not have the classic leaves, but have transformed leaves, which are like flattened twigs, called phyllites.
The inflorescence is composed of a set of globular flower heads from which numerous stamens depart. The large amount of flowers gives this plant a special charm.

Cultivation techniques

The ideal soil for flowering is basically acidic, with a good structure, which ensures a good humidity, but at the same time a good drainage. It is advisable to bring organic substance (humus) periodically (once a year), this is both to ensure the plant the supply of the right nutrients, and to improve the soil structure. The mimosas that show phyllites are more resistant to low-acid soils
The best time to plant the mimosa is from October to March. In colder areas it can be grown in greenhouses with the foresight not to drop the temperature below 0 degrees. The vase must be changed approximately every two years. It should be remembered that the diameter of the vase must not grow excessively, both for an aesthetic factor and to preserve a correct proportion between the aerial apparatus and the radical one.

Foliage Tendentially persistent
Height From 5 to 10 meters
Culture simple
Maintenance low
Water needs low
Growth fast
Propagation Seed, sucker picking, layering, grafting
Rusticity / minimum temperature Slightly rustic / up to -3 ° C
exposure Sun
Ground Poor, well drained
pH Acid or neutral
use Isolated specimen, hedge, grove, large pot, climbing vine

Mimosa characteristics

The acacia dealbata is a medium-sized tree: generally, in the places of origin, it does not exceed 20 meters in height, while in Italy it is rare that it reaches 5. The foliage takes on a wide cone shape over the years. The leaves, tendentially persistent, are bipinnate, up to 12 cm long, divided into numerous linear leaflets, of about 5 mm. These, not toothed, are instead slightly hairy and blue-green.
The bark is smooth and goes from green to glaucous, but, as the years go by, it progressively darkens until it becomes almost black. The flowers, produced at the end of February, are very small, with bright yellow petals and numerous showy and very fragrant stamens. They are harvested in large clusters, evolving later into pods about 8 cm long, flat, initially glaucous then brown when ripe.
The growth is very rapid (even 60 cm per year), but the average life of a specimen is quite short (rarely exceeding 50 years). Moreover, they are often severely damaged by winters with temperatures below the average: in fact, it is a rather sensitive tree at low temperatures. Cultivation in the open ground is worthwhile only where the climate is particularly mild. Elsewhere it is however possible to keep the specimens in large pots, working with careful pruning.
This species is the most widespread among us, but in cultivation there are many others and both habit and some peculiar characteristics can vary.

Mimosa climate and exposure

Mimosa, to grow and flourish at its best, needs high temperatures, lots of sun and well-drained soils. In winter the temperatures should never fall below 5 ° C because the plant does not suffer damage. However, the most serious problems can arise in the presence of frosts, in particular with temperatures between zero freezing and -3 ° C. From this point of view, freezing winds are also to be avoided: if we live in an area with a climate that is not totally mild, it is a good idea to place the trees in an area that is as sheltered as possible, perhaps near a wall facing south.

Land and uses

Absolutely does not tolerate clay or heavy substrates, especially if characterized by the strong presence of calcium: in fact, the onset of leaf chlorosis, which has repercussions on the general vitality of the tree, is very common.
Instead, light and sandy soils or those with an acid pH are preferred.
The uses are very many: both as an isolated specimen, and for the creation of small woods (perhaps varying the species, so as to prolong the flowering period). However, they are at least 4 meters apart, because the superficial roots tend to occupy a very large area and sometimes cause the deterioration of what surrounds them. From this point of view, special attention must also be paid to monitoring them if they get too close to a building.
Also nice to create hedges along the coasts or take advantage of the length of the branches to use them as climbers: they can easily cover arches and pergolas.

Plant the mimosa

Planting takes place from autumn to spring. It is almost everywhere advisable to proceed in spring, to avoid any frosts that could irreparably damage a young tree.

Mimosa in the ground

We dig a large and deep hole at least twice the earth's bread. On the bottom we create a thick draining layer with gravel or expanded clay beads. If our soil turns out to be rather compact it will be a good idea to replace it completely or mix a good quantity of river sand and a little peat.
It is important to simultaneously insert the plant and a resistant tutor, at the same depth, about 30 cm from the foot. After covering with the remaining substrate and having compacted well we tie the trunk in several points to the support. In the early years of life, in fact, mimosas have a very superficial root system and the epigeal part is also very fragile. Without a support it is common for trees to be uprooted by the wind or for the trunk to break open.
As with all members of the Leguminosae family, nitrogen-based fertilizers are not absolutely necessary and therefore it is necessary to avoid the insertion of manure or compost in the hole.
In full ground it is not necessary at this stage to irrigate.
The specimens purchased are mostly grafted onto Acacia retinoides. This species (also called Mimosa of the four seasons) is more resistant to cold and adapts well to calcareous soils. The point of grafting is however rather sensitive to rots and it is necessary to avoid that it directly touches the ground: we therefore leave a distance of at least three cm.

How to grow mimosa in a vase

If we live in an area with cold climate we can choose to grow mimosa in a vase. In this case it is good to turn to specialized dealers addressing possibly to varieties with a more limited development.
We choose a container of adequate size (at least 40 cm deep): the root system becomes important in a short time and we must avoid having to resort to repotting often. In these conditions, the specimen generally manages to grow well up to at least a height of 3 meters.
On the bottom we have to create a thick draining layer with expanded clay. Then we create a substrate by mixing a generic soil with peat, in equal parts. If desired we can also add a few handfuls of coarse sand.
We lightly irrigate and keep the substratum always slightly damp (but not wet!), Particularly from spring to autumn.

Mimosa cultivation

The specimens in the garden almost never require irrigation: it is necessary to avoid excesses of humidity at the root level.
The young trees are very sensitive to low temperatures until the trunk is well lignified. The first few years can therefore be used to cover the subjects with one or more layers of non-woven fabric and to create a thick mulch at the foot level.

Mimosa pruning

Pruning takes place in spring, at the end of flowering: this, in addition to favoring a compact and harmonious growth, will avoid the appearance of pods, which are not very pleasant and, consequently, an excessive self-dissemination.
One must also intervene with a certain frequency to eliminate jets coming from the foot that weaken the hair.
At the end of winter we can instead intervene by eliminating the branches that may have been compromised by frost.

Flowers collection

The flowers are harvested between the middle of February and the end of March: we pick the bunches when the first corollas begin to open: the bouquet will last longer once in our homes.

Mimosa propagation

It is a rather simple tree to multiply. You can proceed through:
- Sowing in the warm: after leaving the seeds in boiling water for about 48 hours, they are placed on a warm bed (or outdoors, from April).
- Picking of root suckers in spring.
- Grafting: it is usual to proceed by approximation using plants obtained from seed that have at least 18-20 months (on a. Retinoides.)

Mimosa diseases

The most frequent parasites are scale insects and metcalfe.
The former are fought with white oil activated by possibly systemic insecticides.
The latter are prevented by choosing well sunny exposures and often wetting the hair. Powerful jets of water can also be useful in removing eggs and larvae, which are difficult to reach by insecticides given the thick, waxy layer that surrounds them.
A common physiopathy is chlorosis: it is frequent, mainly on non-grafted plants, in soils with neutral or alkaline pH. It is prevented by distributing large doses of iron sulphate (which helps to acidify) by the end of the winter. Generally two or three administrations are sufficient after 10 days. In the most serious cases, chelated iron can be used.

Mimosa - Acacia dealbata: Variety

Large species (garden)
- dealbata: the most common. It grows quickly and produces large clusters of fragrant flowers. Watch out for roots that can damage buildings and other trees!
- baileyana larger flowers, at the end of winter, and glaucous leaves. Up to 8 meters high. Weeping habit.
- pycnantha: up to 4 meters high. The flowers are very large and of a beautiful golden yellow. Rapid growth, erect habit. Very sensitive to alkaline soils.
Small-sized species (also from pot)
- drummondii: yellow flowers in April. Up to 1.50 m
- cardiophylla: dark yellow flowers, in April, and bronze foliage. Up to 3 m.
- motteana: Lemon-yellow flowers at the end of autumn and glaucous foliage. Up to 3.5 m
- aspera: Bright yellow flowers, between January and March. Silky leaves. Up to 2.5 m.
Species that tolerate calcareous soil
- saligna sulfur-yellow flowers, decombant growth habit, up to 4 m.
- retinodes small and fragrant flowers, in continuous production. Up to 3 meters. Rustic up to -7 ° C. Controllable roots.
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Planting September - October / April-May
Flowering - harvest February - March (there are also varieties with autumn flowering)
pruning April May
Sowing April May