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.
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.
|Height||From 5 to 10 meters|
|Propagation||Seed, sucker picking, layering, grafting|
|Rusticity / minimum temperature||Slightly rustic / up to -3 ° C|
|Ground||Poor, well drained|
|pH||Acid or neutral|
|use||Isolated specimen, hedge, grove, large pot, climbing vine|
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.
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.
THE CALENDAR OF MIMOSA
|Planting||September - October / April-May|
|Flowering - harvest||February - March (there are also varieties with autumn flowering)|