What is Paulownia?

Historical notes

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The paulownia tree (in Latin paulowania), or paulonia, in the world also known as Princess tree, Kiri tree, tree of life, Adam tree, Empress tree, fox-glove tree, is a deciduous plant belonging to the Paulowniaceae family originally from China and for centuries also planted in Japan (Kiri in Japanese means "life"), where it is considered a sacred tree, bearer of happiness and prosperity, with a high symbolic value for the nation (just think that paulownia is also depicted on a Japanese coin).

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At the beginning of the 19th century, the German naturalist Philip Franz von Siebold, returning from a visit to Japan, returned to Europe bringing with him some seeds of the Kiri tree, and in homage to Anna Pavlovna Romanova, daughter of Paul I, Emperor of Russia, which had financed the Asian mission, decided to give the tree the name of Paulownia, Anna's patronymic name; later the Japanese also began to call the Kiri with the European name of Paulownia.

The Tree

The paulownia is a genus of plant belonging to the Paulowniaceae family which includes over 20 species, among which the best known are the tomentosa, the elongata, the fortunei, the kawakamii, the catalpifolia, the Taiwanese, the fargesii.

It is the fastest growing tree in the world, with huge leaves (up to 80 cm in diameter), large melliferous flowers that can come in different colors, a large crown, and which can well exceed 1 meter in diameter and reach 30 meters in height; while preferring loose, deep and well-draining soils, paulownia adapts to almost all types of soils and climates, being able to withstand very high temperatures as well as very rigid climates. In China, a country from which paulownia comes from, as mentioned, the tree is grown on an area of ​​over 2 million hectares, half of which is grown alongside that of other crops using the inter-rows spaces.

One of the most interesting aspects of paulownia is that after each cut, the plant regenerates itself, can be cut several times (from 4 to 7-8) and survive even up to 100 years; after each cut, therefore, it will not be necessary to replant the tree, which will regrow more vigorously and faster by taking advantage of the root system developed before the previous cuts.  

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Paulownia wood is very light, light and resistant, to the point that it is also called "aluminum wood"; thanks to its unique characteristics and extraordinary quality, as will be seen in another section, it is used for multiple processes; the bark is smooth, light gray in color, and the leaves, which in the first year are very large and fibrous, tend to become smaller over the life of the tree.

 

The tree has a spring flowering that can last over 2 months, with large bell-shaped flowers that can be blue-lilac or white, with a pleasant scent and melliferous; the large foliage and the luxuriant flowering make the plant ideal for urban green projects and parks.

 

The root system of paulownia is formed by an umbrella-shaped root which usually penetrates the ground up to a maximum depth of 1-1.5 meters, and a taproot which can reach depths of up to 8-9 meters; due to this root system, paulownia is often used in order to settle areas at risk of erosion, landslides or landslides.

Another peculiar feature of paulownia is that in practice it is not subject to attacks by termites, insects and various parasites, an element that makes cultivation easy and does not involve the use of chemicals.

As for the contribution that the plant can make to the environment, it is well established that paulownia is the tree with the greatest absorption of carbon dioxide in the world.

For what are the most important characteristics, it is worth spending a few words below, especially with regard to:
 

ADAPTABILITY TO SOILS AND CLIMATES

As mentioned, and as it will be better described in the specific sheet, paulownia adapts to different types of soils and different climates. As for the soils, the plant, although preferring light, deep and draining ones, grows in any type of soil; as far as climatic areas and temperatures are concerned, some clones of paulownia resist temperatures up to +45 and -30 degrees celsius, and also have excellent resistance to drought.


However, it is clear that in the case of commercial plantations, particularly favorable soils and climatic conditions should be preferred, in order to optimize the return on the initial investment (see in this regard the paragraph "optimal growth conditions")

FAST GROWTH

As mentioned, paulownia is the fastest growing tree in the world. In ideal conditions, and with proper care of the plantation, the best paulownia clones can reach and exceed 35 cm in diameter and 15 meters in height in 4-5 years. In any case, for the purposes of a commercial plantation, it is always advisable to consider a period of 6-7 years before arriving at the first useful cut, in order to reach trunk dimensions with adequate commercial value on at least 80-90% of the plants.

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THE WOOD OF PAULOWNIA

From the paulownia tree a beautiful straight-grained wood is obtained, light in color, very light but with an incomparable weight / strength ratio, which has led it to obtain the definition of wood aluminum.

Wood has extraordinary properties, which make it unique; among these it is worth mentioning the following:

  • Lightness: some paulownia clones weigh much less than 300 kg per cubic meter

  • very great dimensional stability

  • excellent insulating properties (sound-absorbing and thermal, electrical and hygroscopic insulation)

  • fire resistant; paulownia wood burns at over 400 degrees celsius

  • water repellency: wood has a very low moisture absorption, and consequently also exposed to the most diverse atmospheric agents, does not change shape and size, and does not decompose

  • resistance to parasites: the high value of the tannins contained in its wood makes paulownia almost unassailable by termites and other parasites

  • absence of knots: the paulownia trunk, if correctly grown, is perfectly straight and free of knots

  • resistance to torsion, compression and bending: paulownia wood has a compressive strength index that exceeds 280 kg per cm2
     

For all the above characteristics, it is evident that paulownia wood can be used for the most diverse applications, as will be seen below.

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LEAVES
 

The leaves of paulownia, which in the first year are very large and fibrous (they can reach 80-90 cm in width), tend to become smaller over the life of the tree; they are rich in proteins (up to over 20%) and microelements, with good digestibility. For these reasons, the leaves are often used in animal feed (cattle, sheep, goats), but are also often used for the production of biofuels

THE FLOWERS
 

The paulownia outsiders are characterized by their size and bell shape; spring flowering can last over 2 months and the flowers may be blue-lilac or white, with a pleasant scent. From the flowers of paulownia a precious honey is obtained, and a plantation can produce over 500 kg of honey per hectare.

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ENVIRONMENTAL ASPECTS
 

ABSORPTION OF CO2

Paulownia helps clean the polluted air of harmful gases and particles, which reach high concentrations, especially in large industrial cities. Paulownia absorbs up to 10 times more CO2 than any other tree species in the world, releasing large amounts of O2 through photosynthesis. Each acre (less than half a hectare) of trees can absorb 13 tons of harmful CO2 particles and gases from the air every year, and release about 13 pounds of oxygen per day, helping to purify the air of pollutants. All this is made possible by the large leaves of the Paulownia tree which, for this reason, can be described as the "green lung" of our cities. Companies and industries that, for their activities, emit polluting substances, can receive (free allocation) the so-called “carbon credits” (or “emission quotas”), in order to offset their CO2 emissions; moreover, companies can buy these shares on the ETS market, as if they were any financial asset.
 

LAND REMEDIATION

Paulownia is a tree with great adaptability, capable of growing even in soils polluted by heavy metals and toxic substances. By absorbing these substances, it therefore helps to reclaim land that would be difficult to use for other crops, purifying the soil and the water inside. Furthermore, once fallen, the large leaves fertilize the soil and enrich the soil with natural humus.
 

SECURING RISK AREAS

Thanks to its root system, paulownia is often used in the fight against soil erosion, in order to settle areas at risk of landslides and landslides.