Citation: Jakubowski, M. Cultivation
Potential and Uses of Paulownia
Wood: A Review. Forests 2022,13, 668.
Academic Editor: Miha Humar
Received: 4 April 2022
Accepted: 24 April 2022
Published: 26 April 2022
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Cultivation Potential and Uses of Paulownia Wood: A Review
Department of Forest Utilization, Faculty of Forestry and Wood Technology, Pozna´n University of Life Sciences,
Wojska Polskiego 71 A, 60-625 Poznan, Poland; firstname.lastname@example.org
This review aimed to determine the current state of research on the growth conditions
and use pertaining to paulownia wood, mainly in European countries where paulownia has been
introduced only relatively recently. Several studies carried out on Paulownia hybrids have shown
signiﬁcant differences in the growth dynamics of individual clones in their response to local environ-
mental and climatic conditions. For example, dry biomass production yields in the second year of
cultivation range from 1.5 t ha
to as much as 14 t ha
. This diversity has manifested itself not
only in growth characteristics but also in the properties of the wood and the possibilities for its use.
Despite having clear similarities to the genus Paulownia, the cultivation of species and hybrids under
different conditions has produced varying results. The best growing conditions for this wood (that
make economic sense) are in the Middle East and Southern Europe. These regions have accumulated
the most experience because of the earlier establishment of the crop. Today, paulownia cultivation is
dominated by hybrids with selected traits that are propagated mainly in vitro. The most commonly
planted hybrids include the clones
112, Cotevisa 2 and Shan Tong. The growth results and
production capacity in central European countries are lower compared to Southern Europe. Ex-
periments on paulownia cultivation are still relatively young, mainly consisting of replicating the
cultivation of hybrids developed in Asia or Southern Europe. However, agronomic procedures are
being developed and reactions to local climatic conditions are being studied. It is likely that, in the
next few years, the proﬁtability of growing paulownia in these regions will become apparent.
Keywords: hybrid; biomass; wood properties; fast-growing; plantation; cultivation
Climate change has led to a rapid increase in research into reducing carbon dioxide
) emissions. One form of reducing CO
emissions is the use of alternative energy
sources, including biomass. Various forecasts have predicted a steady increase in de-
mand for the use of wood and wood-based materials until at least 2050 [
]. There is a
rapidly growing interest, worldwide, in fast-growing wood species that can be used for
]. As one of the fastest-growing tree species in the world, the genus Paulownia
has attracted enormous interest from academia and industry in recent years. Several re-
search programs have been launched and experiments performed in order to verify the
possibility of growing and using paulownia wood as a raw material [
]. These research
programs are being carried out simultaneously across a variety of ﬁelds, and their number
is growing by the month. On the one hand, this is a positive development, leading to a
broad exploration of the possibilities of using paulownia, but on the other hand, numerous
limitations are being discovered. Doubts have also been expressed about the previous
optimism regarding universal fast-growing species. The genus Paulownia is native to China
but has quickly gained popularity throughout Asia, the USA, Australia, and Europe [
Research on its cultivation has also been conducted in central Africa [
]. The aim of this
review was to determine the current state of the research on its growing conditions and
areas in which paulownia wood can be used, mainly in European countries and the Middle
East, as these areas have seen increased interest in paulownia wood over the last 20 years.
Forests 2022,13, 668. https://doi.org/10.3390/f13050668 https://www.mdpi.com/journal/forests
Forests 2022,13, 668 2 of 15
Paulownia tomentosa (Thunb.) Steud and P. fortunei (Seem.) Hemsl. are genera/species
of plants that belong to the family Paulowniaceae but that were historically included in
the genus Catalpa Scop. and the family Scrophulariaceae. Modern genetic research has
updated the systematic afﬁliation of Paulownia. Further distinctions were made in the
families Scrophulariaceae and Bignoniaceae, leading to the new family Paulowniaceae
being separated out, the Paulowniaceae being genetically closer to the Lamiaceae than
the Scrophulariaceae [
]. There is currently no consensus on the number of species of
Paulownia, with between six and a dozen species being listed [15,19].
The name ‘paulownia’ was given to the tree in honor of Anna Pavlovna Romanova,
Grand Duchess of Russia, and later, Queen of the Netherlands, who sponsored Philipp
von Siebold’s second expedition to Japan in 1861 [
]. The tree has an umbrella-shaped,
low-set crown, and the green parts of the plant are covered with ﬁne hairs. The bark is
grey-brown or black, smooth, and covered with numerous lenticels, with vertical cracks
appearing with age. The young plant develops large leaves that are 15–30 cm long and
10–20 cm wide (P. tomentosa); in older plants, these are smaller [
]. Paulownias develop
many branches in the wild but will develop a single trunk in close quarters or with speciﬁc
pruning techniques. Eight years of research into different techniques, including budding
branches and pruning development, have yielded varying results. Optimal results have
been obtained for moderate-intensity pruning as the best solution for rapid growth in
budding branches and the development of an extended trunk [
]. Paulownias have a deep
and well-developed root system that forms several branches and usually reaches depths of
2 m. Recorded examples of root systems that are nearly three times as wide as the crown
have been reported [
]. Their strong and rapidly growing root systems can also penetrate
to greater depths under favorable conditions and can be used, for example, to stabilize
Paulownias reproduce generatively and vegetatively; however, under industrial con-
ditions, reproduction is almost entirely vegetative. Historically, the oldest reproduction
method has been via root-splitting, which is also used for natural species [
at an early developmental stage—known as the mini-cuttings technique [
the rooting process for green cuttings [
] have also been used. However, the primary
means of propagation for many clones is via
]. One of the most
important steps in the reproduction phase is the production of a healthy, well-developed
root system, so some of the research has focused primarily on this issue [34–36].
The most commonly cultivated species are P. tomentosa,P. elongata,P. fortunei,
P. taiwaniana,P. fargesii,P. galbrata and P. catalpifolia [
]. In the early introduction
of paulownias worldwide, pure botanical species were used. One of the ﬁrst countries to
introduce it on a large scale was the US, with paulownias (P. tomentosa) being imported
around 1840. Because of its quick growth, it was named “the tree of the future”. Over the
past 150 years, it has spread throughout the various states, causing a great deal of trouble
that has resulted in a heated debate regarding all species of Paulownia.Paulownia tomentosa
has ofﬁcially been declared an invasive species, so much so that it has been eradicated
from many states. More lenient treatment has been given to P. elongata, which is not as
invasive but is also accepted reluctantly. Paulownia in the US has as many opponents as
supporters, and discussions regarding the genus are heated because the existing crops
make their owners substantial proﬁts .
Recent studies have shown that P. tomentosa can spread in areas where stands have
been damaged by various disasters and disturbances, especially in the canopy [
some countries, certain species of Paulownia have been declared dangerous, such as
Forests 2022,13, 668 3 of 15
P. tomentosa, which has been recognized as an invasive species in Austria [
]. The Czech
Republic, too, has taken note of it, giving it the status of an alien species requiring constant
]. State authorities in Poland have also been cautious about the introduc-
tion of paulownias on a mass scale [
]. Natural Paulownia species are still being grown
throughout Asia, as far as Turkey, but are increasingly being replaced by hybrids. In some
countries, such as Bulgaria, hybrids have only gained importance as a potential product af-
ter previous attempts to cultivate pure species failed [
]. For the production of hybrids,
individuals are selected from several popular species that exhibit high productivity and
high environmental adaptability, including P. elongata
P. fortunei [
] and P. fortunei
P. tomentosa [
]. Some of the best-known hybrids are the clones
Cotevisa 2, Sundsu 11 [
] and Shan Tong [
]. Examples of less well-known hybrids
include Arctic [
] and the selected genotypes PWCOT-2, PW-105, PWL-1, PWST-33 and
]. There are also naturally occurring hybrids, such as P. taiwaniana from a
cross between P. kawakamii and P. fortunei [
]. Sometimes, more unusual hybrids are
found, such as the 9501 ((P. fortunei
P. tomentosa)) [
paulownia plantations are established at a speciﬁc density depending on the end-use. They
are usually planted at a spacing of 2
. For biomass production, about
2000–3300 plants/ha are planted, while for timber production, far fewer are planted, about
550–750 trees/ha [
]. Paulownia hybrids are grown in short, 6–10-year cycles for their
roundwood, but these cycles can be even shorter for biomass .
2.3. Growth Conditions
The most well-known feature of paulownia is its ability to reach gigantic sizes in a very
short time. In China, it has been said of the paulownia that it “looks like a pole in one year,
an umbrella in three years and can be cut into boards in ﬁve years” [
specimens have been described in China, such as the 80-year-old P. fortunei growing in
Kweichow Province, which reached a height of 49.5 m, a diameter at breast height (DBH)
of 202 cm and a wood volume of 34 m
; another, at 90 years of age, had a 224 cm DBH and
wood volume. Among the younger trees, an 11-year-old P. fortunei, grown in the
Guangxi Zhuang Autonomous Region of southern China, measured 22 m tall and had a
DBH of 75.1 cm with a wood volume of 3.69 m
. Similar sizes have also been achieved by
P. elongata [
]. Under native conditions in China, paulownias typically attain a 30–40 cm
DBH in 10 years and produce around 0.3–0.5 m
of wood, although in optimal conditions,
useful wood can be produced in 5–6 years [
]. Using natural species as crops has been a
popular undertaking in China and Southeast Asia for centuries. Compared to other species,
paulownias perform very well in terms of growth dynamics, even compared to the fastest-
growing poplars [
]. Other studies have conﬁrmed that, compared to other fast-growing
trees, such as willow, poplar, eucalyptus and red oak, paulownias achieve by far the
greatest growth under optimum conditions [
]. These conditions—-especially light levels—
-impact photosynthesis, which paulownia growth beneﬁts from under optimal conditions
and is limited by unfavorable conditions. This tree requires light intensities of between
20,000 and 30,000 lux for optimal growth [
]. Paulownias perform photosynthesis based on
C4-cycle enzymes [
], as opposed to the classical C3-cycle characteristic of most plants [
Their greater photosynthetic efﬁciency in the right conditions enables paulownias to gain
weight quickly in a short period. Although C4 mechanisms are present in paulownias,
hybrid lines tend to exhibit C3 activity [
]. The activity of enzymes involved in the
C4 cycle is highly variable and often limited. Paulownias are greatly affected by their
growth and development conditions, especially the stress caused by drought or salinity,
for example [
]. Through these mechanisms, paulownias can show high adaptation
to environmental stress conditions. However, their intensive growth requires a great deal
of water—from 1000 to 2000 L per seedling in the ﬁrst growing season [
]. Studies have
emphasized the particular importance of watering in the ﬁrst months of growth [
The water supply can also contribute to the production of more leaves and, consequently,
increased shoot growth [
]. Paulownias require permeable soil with a pH value above
Forests 2022,13, 668 4 of 15
5 (5–8.9) and an optimum temperature of 15–16
C. Researchers have pointed out, however,
that mass production greatly depends on soil quality, as expressed by the soil quality
]. Because of the rapidity of paulownia biomass production, there may be notable
changes in the soil. After one year of soil monitoring, it was found that some microbiological
parameters had decreased around the trees, which was related to a decrease in the nutrient
]. Other researchers have reported similar changes related to soil microbial
activity and the soil’s microbial community [
]. One proposed solution has been the use of
residues produced by the forest biomass industry. This mainly involves the use of pine bark
and ash biomass. Soil enriched with these components can maintain a balance between
microbial activity and the community .
Paulownias have shown sensitivity to soil salinity, which is often a characteristic of
semi-arid regions. Sometimes, this condition can be intensiﬁed by the evapotranspiration
of the paulownia. This susceptibility is not the same for all Paulownia species; it has been
recommended that lines of resistant hybrids should be developed [
]. Stress caused by soil
salinity can enhance the effect of high light stress, consequently reducing photosynthetic
]. The optimum air temperature for rapid paulownia growth is 27
C but the
spectrum of extreme temperatures that they can tolerate is broad, ranging from
]. However, these values vary by species, the natural tolerance of minimum tem-
C for P. tomentosa,
C for P. elongata and P. catalpifolia,
C for P. fortunei,P. kawakamii and P. fargesii. Introduction experiments
conducted in China have resulted in only partial survival at lower temperatures [
hybrids are currently being grown mainly in southern Europe, where severe frosts do not
occur, there is no conﬁrmed data on the frost resistance of introduced hybrids. However,
some observations have been made on the survival of young seedlings in regions where
frosts and freezing occur. Seedling survival in Turkish experiments on seedlings that
originated in China was determined to be 60–90%, with one experiment resulting in only
a 50% survival rate [
]. In Northern Ireland, where the conditions are quite different,
survival ranged from 70% to 95% for hybrids with Spanish origins, except for one study
where the survival rate was only 20%, while the survival of hybrids with Moroccan origins
ranged from 30% to 33.3% [
]. Some authors have also reported that all their seedlings
died in winter. Ulu et al. [
], in one of their experiments, reported that all the seedlings
growing in Gölköy, Turkey (at 1400 m) died during the winter of 1999. Other authors have
also reported signiﬁcant numbers of young seedlings that did not survive the winter [
Some studies have pointed to frost as being particularly damaging to the growth of young
paulownia seedlings when the shoots are green—-that is, at the beginning of winter or
during spring frosts. According to the study by Ayan [
], all the top shoots froze in winter.
Research carried out in the Czech Republic has shown unsatisfactory growth due to frost
in the clone
112 in the ﬁrst two years of cultivation [
]. Other researchers have
recorded heavy snow damage in the winter of 2001 at the Ulubey site in Turkey .
Another factor limiting the growth of paulownias is the length of the growing season,
which is variable in Central European climate conditions. In comparing the length of the
growing season of the Paulownia Oxytree (clone
112) in north-eastern Poland, a
28-day shorter growing season was recorded in 2019 compared to 2018 [
have very large leaves in their juvenile state, and the stem is not sufﬁciently woody at
that stage, making it susceptible to mechanical damage. Therefore, another damaging
factor can be strong winds, which, in open conditions, can destroy an entire plantation [
Experiments in New Zealand have shown that young trees and branches are susceptible to
damage from wind speeds as low as 40 km hr
, and that wind can restrict tree growth
even after 3–4 years of age .
Like any plant, paulownias can get sick and are susceptible to various pathogens. The
most well-known disease in paulownia is witches’ broom, a condition that has been observed
in Chinafor many years [
]. Modern studies have determined phytoplasma (a parasite) to
Forests 2022,13, 668 5 of 15
be the causal agent of witches’ broom, which is potentially transmissible between paulownia
]. The mechanism of activity is probably related to gene-expression changes in
response to the phytoplasma [
]. Some studies have suggested that there may be genetic
resistance to the disease in the cultivar P. tomentosa
P. fortunei [
]. In addition, other
diseases have been found, such as Phytophthora root and collar rot [
] and rot caused by
Trametes hirsuta in Serbia [
]. Recent reports have indicated the presence of nematodes
(Meloidogyne hapla) in the roots of P. tomentosa in Poland [80,81].
3. Paulownia Wood Properties and Uses
3.1. Wood Structure
Paulownias have light yellow to light red heartwood. The boundary between the
sapwood and heartwood is not clearly deﬁned. The sapwood is very narrow and usually
contains one or two annual rings. Annual rings are clearly visible in all cross-sections.
The wood has a ring-porous or semi-ring-porous structure. The vessels are either barely
visible or are not visible at all, and the tree rays are visible only under magniﬁcation [
The vessels are oval in shape and can be divided into early-wood vessels and late-wood
vessels, the latter being 3 to 10 times smaller. Surrounded by a broad band of parenchyma
of varying shapes, the rays are narrow, usually occupying a single row up to 0.5 mm
high, although multi-seriate rays do also occur [
]. The heartwood is sensitive to
discoloration. Several factors can cause such color changes, which can be divided into three
groups—-chemical discoloration, microbial discoloration and photo-discoloration [
aging of the wood also causes distinct color changes, with natural changes being less
obvious than those induced artiﬁcially by ultraviolet light or high temperature [
]. It is
well known that thermal modiﬁcation causes similar color changes in other wood species.
Suri et al.  described these changes in paulownia wood.
3.2. Wood Properties
In terms of their physical and mechanical properties, paulownias are most similar
to willows and poplars. However, the ﬁndings of many of the works on this subject
relate to different crop origins and locations. The experiments that have been carried out
often employed different methodological assumptions; therefore, the results are sometimes
difﬁcult to compare. Paulownia wood density, with a 12% moisture content, ranges from
220 to 350 kg m
, but most often oscillates around 270 kg m
]. Variability in
paulownia wood density is caused mainly by different growth conditions, although this
differs between the species P. tomentosa,P. elongata and P. fortunei, with a slightly higher
density commonly being attributed to P. tomentosa [
]. Occasionally, as indicated by
certain authors [
], a density of above 400 kg m
has been measured (Shan Tong, Bulgaria).
Paulownia wood static bending strength ranges from 23.98 to 43.56 MPa, depending on
the species, while the modulus of elasticity ranges from 2651 to 4917 MPa [
even up to 5900 MPa for P. tomentosa [
]. In both standing-tree and log tests performed
using non-destructive methods, a higher modulus of elasticity has been reported for trees
with larger diameters .
The physical and mechanical properties of paulownias have been found to be subject to
a number of variations during the drying of the sawn timber. Depending on the technological
process used, these variations may be either highly significant or non-significant [
nias have a high strength-quality factor, which equates to a high strength-to-density ratio.
For the Cote-2 hybrid, this has been measured as up to 9.2 km [
]. For specific applications,
this is a most useful parameter, especially where very lightweight but robust structures are
required, such as in composite construction panels [
]. All these data on paulownia wood
indicate quite wide variations in the different species’ properties; therefore, when talking
about paulownia wood, it is important to have a specific species in mind. This issue has been
highlighted by Feng et al. [
], who tested 23 clones and demonstrated a phenotypic variation
in the wood properties of 11.75% and a genetic variation exceeding 19.04%.
Forests 2022,13, 668 6 of 15
3.3. Traditional Uses of Paulownia Wood
The ﬁrst descriptions of traditions related to the use of paulownia wood date back
to several centuries BCE [
]. The tree was used for religious and medical purposes and
was held in high esteem, being associated with birth and death. Many legends have
been associated with the tree, mainly in China and Japan. The widespread cultivation
of paulownias has been known since the third century CE [
]. Today, the wood is often
used because of its popularity and its ability to grow under a wide range of conditions.
Paulownia wood is used in plywood, engineered wood (other than construction wood),
paper, veneers, hand carvings, clogs, furniture and kitchen items, such as rice pots, water
buckets, bowls, spoons and sticks [
]. A frequently mentioned use for paulownia
wood is in the manufacture of musical instruments [
]. Speciﬁc acoustic parameters
that are not found in spruce wood may cause it to be replaced by paulownia in some
instruments, resulting in new sounds. However, as a material that might be suitable for
musical instruments, paulownia wood does not work well as a sound absorber. Paulownias
have large vessels, but low through-pore porosity because of the large number of tyloses in
the vessels. Therefore, gas permeability is low and sound absorption is poor. This reduces
its quality as a soundprooﬁng material compared to balsa or binuang [
]. It also limits
the use of paulownia in applications where wood saturation is required [102,103].
One solution to this problem is the thermal modification of the wood. As determined by
], the gas permeability and sound absorption coefficient of heat-treated P. tomentosa
increased as a result of heat treatment, depending on the temperature. Kolya and Kang [
reached a similar conclusion, recommending hydrothermally treated paulownia for sound-
absorption boards in housing applications. Yet another method, based on a supercritical CO
treatment, has been proposed by Xu et al. [
]. Researchers have shown that this method
significantly improves the gas permeability of P. fortunei as a result of the reduction in the
proportion of cells with tyloses [
]. Tests for suitability in the manufacture of pencils and
crayons have also been positive, with tests comparing paulownia (P. elongata) wood to poplar
(Populus tremula) and juniper (Juniperus excelsa), which are commonly used in these products,
having shown great promise in terms of wood properties .
3.4. Pulp Industry
The utility of P. tomentosa in the pulp industry was pointed out decades ago in the US;
however, researchers have stressed that paulownia ﬁbers are short and are only suitable
for certain grades of paper [
]. Contemporary research has veriﬁed this knowledge
in a broader context. As determined by San et al. [
], based on a study conducted on
a 3-year paulownia plantation, the ﬁber sizes take on values typical of the deciduous
species useful in this industry. However, it is always important to bear in mind the speciﬁc
species in question because, while the ﬁber lengths of the various species of Paulownia
are similar, ranging from around 0.82 to 1.002 mm, the thickness of the cell wall varies
considerably. For example, the average thickness of the ﬁber cell wall can vary from 3.8 to
m between the different species of Paulownia [
]. Its high cellulose content (47.85%)
makes it useful for the pulp industry, as indicated by Popovic and Radosevic [
also, however, noted that the chemical composition differed between the various species.
Similar relationships and the suitability of Paulownia for cellulose production have also
been pointed out in other studies [
], whereas in later studies, the bioreﬁnery of
paulownia wood has been improved in order to obtain lignocellulosic biomass for fuels,
solvents and chemicals, etc. [
]. Due to paulownia wood’s short production cycles, both
the stem and branch wood can be used, although the latter is of lower value and is often
accompanied by reaction wood; however, this can be used in paper, nanocellulose, charcoal
and other applications [82,114,115].
Forests 2022,13, 668 7 of 15
3.5. Energy Goals
Nowadays, paulownia plantations oriented toward biomass production are gaining
in popularity [
]. This tree can produce as much biomass in a year as other species can
in a few years [
]. Suitable hybrids work best in this field, but the differences between
the hybrids and the regions where the experiments were carried out are quite significant.
Studies have shown that, for example, the clone Cotevisia 2, grown in Spain, has 1.8 times
the productivity of the clone Suntzu 11. However, in two locations out of the six stud-
ied, it was Suntzu that yielded higher productivity. Both clones in the 2-year experiment
showed record productivity in the Villanueva del Río y Minas region (Sevilla province,
Spain), where between 7.2 and 14 t of dry matter were harvested per hectare (i.e., 3.2 and
7.4 t of C, respectively). The same clones in another region of Spain (Cordoba) showed
productivity ranging from 1.7 to 2.3 t of dry matter [
]. By comparison, a 16-year ex-
periment conducted on P. tomentosa in Asia yielded 38.8 t C ha
, while a 21-year experi-
ment yielded over 105 t C ha
]. The experience of other researchers has also indicated
that biomass production greatly depends on the hybrid used for the crop. As an exam-
ple, Berdon et al. [
] determined very poor productivity from clone X1 compared to three
others (112, COT2 and L1) based on a 3-year experiment conducted in southern Spain.
Baier et al. [
], in a study conducted near Lake Issyk-Kul (Kyrgyzstan), demonstrated
biomass production of between 1.52 and 3.41 kg per tree per season, with water consumption
of between 433 and 613 l. Gyuleva et al. [
], reporting on a 5-year experiment that compared
the productivity of two paulownias introduced into Bulgaria, showed that the best results
came from the southwestern part of the country. Paulownia tomentosa had higher productivity
of 3.479 t ha
(oven-dried biomass) after 2 years of growth and 36.995 t ha
after 4 years,
while the productivity of P. elongata
P. fortunei was 2.730 t ha
after 2 years and 19.964 t ha
after 4 years. On degraded soils, paulownias show a very low growth rate. In a 3-year study
in Spain, a biomass yield of P. fortunei of only 3.34 t ha
was achieved, which was very low
compared to the parallel-grown Eucalyptus globulus (40.4 t ha−1) .
As a tree with a high growth rate but low wood density, paulownias do not perform
well at producing efficient fuel. A comparison of pellets, in terms of European standards,
produced from young P. elongata
P. fortunei plantations showed their poor quality
compared to Pinus radiata and Eucalyptus nitens pellets [
]. In another study, however,
evaluating the production of briquettes and pellets from sawdust, satisfactory energy
effects were obtained for P. tomentosa and P. elongata [
]. It may be appropriate to
first apply biomass torrefaction, as proposed by ´
Swiechowski et al. [
], in order
to get a better starting quality for fuel production. The calorific value of paulownia
alone is close to that of the energy species already grown in Europe. The tested hybrids
(9501 and Shan Tong) produced only slightly lower gross calorific values of 19.5 MJ
(hybrid 9501) and 19.6 MJ kg
(Shan Tong) than willow (19.9 MJ kg
poplar (19.8 MJ kg
). By contrast, the OXI hybrid (19.2 MJ kg
) had a lower calorific
]. Similar values have been provided by Zachar et al. [
] for P. tomentosa
(19.71 MJ kg−1).
However, today’s economies require much more rapid results than are obtainable
from years of observation during various experiments. To some extent, this process can
be, and has been, accelerated by building mathematical models and forecasting crop
development under different local conditions. As experience has shown, such models
have a great future and can highlight favorable vs. unfavorable phenomena at an early
stage. Stankova et al. [
] showed using a model that variability in dendromass
production depended on the species and crop type, with variability ranging from 0.3 to
4.5 t ha
of dry matter. They also proved that most biomass is accumulated in the trunk,
and only 35% of juvenile trees have branches. However, modeling faces several problems
due to the complexity of the criteria that can affect forecasting, although the models are
constantly developing. This is especially true for biomass planning and the forecasting
of wood properties [
]. In a recent analysis, Iran, which has some experience
in introducing paulownia cultivation, forecast the capacity for paulownia cultivation in
Forests 2022,13, 668 8 of 15
an area of 160,000 km
]. Introducing paulownias as an important element in
biomass production needs particular consideration in countries with favorable conditions
for the growth of hybrids that may be competitive with native species. Research in this
area is ongoing in Spain [
], Romania [
], Portugal [
], Italy [
], Iran [
], Serbia [
], Ukraine [
] and Northern Ireland [
], among others.
3.6. Other Modern Uses
There is currently much research being conducted that is aimed at furthering the use
of paulownia wood in the production of wood plastics and composites [
] and in
the production of biopolymers [
]. Paulownia wood also performs well in the production
of blockboards, which act as a core layer between veneers [
], and as an ingredient for
the production of lightweight particleboards [
]. It can also be subjected to thermal
modiﬁcation [144–146] or can be improved by other methods, such as high-pressure treat-
ment, which works well for low-density woods such as paulownia [
wood can undergo pyrolysis and conversion to gases as an energy source [
] and can be
used as a feedstock for bioethanol production [
]. Work is also underway to examine
the use of paulownia waste as a substrate for producing biohydrogen [
]. In addition to
the wood, the remaining parts of the plant, such as the leaves and ﬂowers, can be used for
medicinal purposes [152–157] and as a food source for animals [153,158–160].
Attempts to use Paulownia species for the phytoremediation of heavy metals in con-
taminated soils have indicated a signiﬁcant accumulation of metals, such as copper, zinc
and cadmium, although this was due to their high biomass productivity rather than their
metal accumulation potential [
]. Another study found a signiﬁcant difference in
lead and zinc accumulations between different hybrids .
Based on the literature review presented here, it can be concluded that the main
purpose of growing paulownia in short cycles is to produce woody biomass for the energy
and pulp industries, as well as for other industries related to wood processing, the creation
of wood composites and biopolymers, and wood gasiﬁcation, etc. To a minor extent,
research is ongoing into the use of other parts of the plant, such as the leaves and ﬂowers, in
the pharmaceutical industry or for animal feed. The traditional uses of wood for furniture-
making and wider mechanical processing is rather limited by the natural occurrence
of Paulownia species and the locations where paulownia trees reach large dimensions.
Experience has shown that pure species, such as P. tomentosa and even P. fortunei, are
invasive so only some hybrids have been accepted into mass cultivation. Considering the
regions involved, the best conditions for the growth of Paulownia hybrids are in southern
Europe, particularly Spain, Portugal, Italy and the Balkans, and in Middle Eastern countries
such as Turkey and Iran, where conditions are also much better than in countries further
north. The number of positive experiences indicates great potential, which, however, varies
The reported technical parameters, chemical composition, requirements for growing
conditions and biomass production differ signiﬁcantly between different species and hy-
brids. The values obtained from the published studies sometimes differ by up to several
dozen percent. Each time, a trial should determine the suitability of the selected species
or hybrid for each speciﬁc purpose. Experiments in Central and Eastern Europe are still
in the early stages due to the late migration of paulownias to these areas. However, there
are already indications of lower production efﬁciency than in southern Europe. Several
factors contribute to this ﬁnding, the most important being the shorter growing season,
which signiﬁcantly reduces seedling growth and biomass production. The second is low
temperatures and frosts in spring and autumn. This does not rule out the possibility of
introducing paulownias into this region of Europe, but further research is required, mainly
to improve cultivation methods in order to best adapt the tree to the speciﬁc climatic
conditions. The use of appropriate frost protection and various agrotechnical treatments
Forests 2022,13, 668 9 of 15
can aid in this. Paulownia and its hybrids offer a serious alternative to many native tree
species in Europe, but it is not a completely universal species and requires further research,
variety selection and improved cultivation methods for introduction into production in
Funding: This research received no external funding.
Conﬂicts of Interest: The author declares no conﬂict of interest.
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