Short Characteristics of Paulownia
Paulownia is the genus of rapid-growing trees from Paulowniaceae family.
Paulownia originated from South-East Asia. This tree is widely-spread in Japan and Central China (for instance, there are 2.5 million hectares of cultivated Paulownia in China!).
All the Paulownia species are rapid-growing trees. When selecting the species the low temperature resistance must be taken into consideration. It’s known, that Paulownia tomentosa is resistant to the temperature -27°С, Paulownia elongata is resistant to the temperature -16°С, and, quite the contrary, Paulownia fortunei is not tolerant to any temperature below 0° С.
The most popular Paulownia species are:
- Paulownia Tomentosa
- Paulownia Catalpifolia
- Paulownia Fortunei
- Paulownia Kawakamii
- Paulownia Taiwaniana
There are also some varieties of Paulownia known as:
- Paulownia “Hybrid”
- Paulownia “Shan-Tong”
Paulownia- Fastest Growing Plant
Paulownia is a real tree of the future!
Literally, all parts of the tree (trunk, leaves, and flowers) are potential source of income. Paulownia grows at an incredible speed (3-5 meters per year or 100 tons of biomass per hectare in 3 years!). Trunk can be chopped off several times (up to 8 times), but the tree would be growing again. Paulownia cultivation can be a profitable business! That is the reason, why its called “wonder tree” or “oil well” tree.
Growth rate of various tree species:
Paulownia is a tree with large, beautiful leaves (70 centimeters in diameter), flowers (6 centimeters in diameter), and gorgeous crown. Trunk diameter is about 1 meter. Life expectation is approximately 100 years. Depending on the environment, the trees can reach various heights up to 25 meters. It’s unpretentious to soil, can be cultivated anywhere, even on dry soils containing up to 2% of lime; but deep, moderately moist, drained, sufficiently fertile, clay soils are the best for growing. It’s also a heliophyte, best grown on open well-illuminated areas.
Hue of the wood varies from silvery-grey to light brown, sometimes with reddish tinge. The wood is highly valued throughout the world as a source material for a wide range of products: construction materials, finishing agents, furniture, interior items, musical instruments, etc.
Paulownia wood is strong, but soft and steady against bending and twisting at the same time.
Due to high density/mass ratio, Paulownia wood is considered as one of the best construction materials. It is easily treated. Many artisans prefer it because of the strength, smoothness and lack of defects.
Mass: Paulownia wood is even lighter than cork wood, which, to this day, has been considered to be the lightest. It is lightweight and extremely strong at the same time, which is ideal, when this balance is required. An average mass of one cubic meter of Paulownia wood is approximately 208-300 kilograms, which is four times lighter than oak wood (one cubic meter has 850 kilograms in weight) and half lighter than pine wood (one cubic meter has 482 kilograms in weight).
Solidity: Paulownia wood has the highest solidity/mass ratio among woody species. Besides, Paulownia is resistant to load deformation and humidity.
Paulownia wood has a low flammability risk. It inflames at the temperature twice as much (400°С) as the inflammation temperature of conifer wood (fir, pine). In ancient times, the Japanese made their wardrobes and chests of Paulownia to keep their property (clothes, jewelry, and valuable papers) safe from the fire.
It is also resistant to the wood-boring beetles and termites.
Stability: Wood air-drying takes at least 30 days. Planks can be dried in ovens at high temperature over 24 hours until the moisture content in wood reaches 10-12%. Dried material doesn’t curl. Shrinkage factor of the wood dried in oven in comparison with green state is only 2.2% crosswise and 4% lengthwise.
Wood cost/tree growth rate and profitability ratio of Paulownia in comparison to other tree species.
Cost: World price of one cubic meter of Paulownia varies from 200 to 800 USD, depending on the degree of processing.
Additionally, due to its ultrafast growth, Paulownia takes the lead over other tree species in the annual mass increase.
Paulownia wood absorbs water insignificantly, which favors mordant and lacquers economy. Goods made of Paulownia wood do not change their shape and size under the influence of severe weather and do not easily decay.
Paulownia as Construction Material
Paulownia as an industrial material was first used in China. Nowadays, Paulownia wood is very popular for building purposes all over the world. Generally, Paulownia wood is used for finishing works as a building material, and for furniture production.
Paulownia wood is actively used for house building. The main advantage of Paulownia wood is that it dries very fast and without any deformation, while the toughness against fracture is very high.
Paulownia wood can be used almost everywhere in home decor. Blinds, piles, beams, ceiling, joists, lining boards, parquet, facing materials, window frames, doors and furniture can be made from Paulownia wood. Paulownia is a perfect material for whittlers due to its softness. Combination of hard ignition and lack of deformation makes this wood an ideal material for the most sophisticated woodcarving. Smoothness and lack of knots are just one of the features in the quality list of this wood. Beams made of Paulownia have a very useful feature they can hold screws at the very edge and do not crack.
Paulownia as Source of BioFuel
Pellets are bio fuel, the alternative “green” source of thermal energy. In spite of a great demand for renewable thermal energy sources, world price for pellets is approximately 100 Euros ton.
Pellets made of Paulownia have considerable heat emission. When being burnt, 1 ton of Paulownia pellets emit as much energy as:
- 480 cubic meters of natural gas
- 500 liters of diesel fuel
- 700 liters of masut
- These pellets are economical and highly efficient when burnt. At the same time, pellets made of Paulownia are more nature-friendly than other wood:
- carbon dioxide emission is 10 to 50 times less
- ash amount is 15 to 20 times less
- lack of sulfur in emissions
Pellets are twice as dense as common wood balls and produce three times much thermal energy (coefficient of efficiency = 96%).
Due to the low flammability risk, pellets made of Paulownia will not ignite spontaneously when the temperature rises.
Because of the low moisture content, pellets made of Paulownia are lighter, which decreases transport costs. These pellets do not absorb moisture from the air, which is why their thermal conduction does not decrease over time.
Paulownia for Heating
Paulownia can be used for production of firewood for house and greenhouse heating; pellets; and bio ethanol, because of the following advantages:
It can be cultivated on poor sandy soil, not using the fertile soil necessary for other crops.
Paulownia plantation does not require special care, which decreases costs.
It does not require re-planting. After being cut down the tree would regenerate. The root system can survive over 70 years, which is 4 to 9 growth cycles after cutting, 8 years each.
The trunk can be chopped off at any time of year regardless of the season or short period of harvesting, unlike other tree species.
When cultivated for firewood, 1000 Paulownia trees are to be planted on the area of 10000 square meters (1 hectare). When pruning one-year old saplings in autumn, up to 7 kilograms of dried mass can be obtained from each tree, therefore 7000 kilograms of dried mass can be gathered from 1 hectare! It would help a family save money on fuel for house and farm heating.
In spring, the root system gives new plant(s), which reaches the same height. Thereby, trees can be grown without re-planting for about 15 years.
Another possible application of Paulownia its production of bio ethanol. American scientists designed a new ethanol synthesis technology, based on both thermo-chemical and biotechnological methods, which gives 511 liters of ethanol from one ton of dried wood. That’s why Paulownia is called an “oil well” tree.
Multiple uses of Paulownia
Paulownia wood is used for the production of furniture, building structures, finishing materials, toys, plywood, and musical instruments.
Paulownia has the largest strength/weight ratio among the woody plant species. Paulownia wood is highly resistant to deformation under the load and moisture, has a low fire risk and is resistant to furniture beetles and termites. Wood air-drying takes at least 30 days. Planks can be dried in ovens at high temperature over 24 hours until the moisture content in wood reaches 10-12%. Dried material does not curl or shrink much.
Paulownia is the perfect tree to produce biomass, because its wood has a high heat emission coefficient.
The combustion of 1 ton of Paulownia wood gives the same amount of thermal energy as the combustion of 480 cubic meters of natural gas, or 500 liters of diesel fuel, or 700 liters of masut. Paulownia wood is actively used for pellet production. Pellets are biologically clean fuel, obtained by a special processing (milling, pressing) of waste wood. Pellets are the alternative source of environmentally friendly thermal energy, which are in great demand in the world market. The price for pellets in the international market is approximately 100 euros per ton.
The leaf mass of Paulownia is used as forage for livestock (cows, sheep, goats, etc.).
Its qualities are similar to alfalfa. Green leaves contain about 20% and dead leaves-about 12% of useful agents, which are easy for digestion. Leaves can grow up to 75 centimeters in diameter, which is why they are the real oxygen factories. At average, the leaves from just one tree absorb 22 kilograms of carbon dioxide and release 6 kilograms of oxygen per year, purifying thousands of cubic meters in the air. Owing to its extraordinary qualities, Paulownia has become an ever-present tree in parks and gardens not only in Asia, but also in USA and Europe.
Paulownia is also grown as honey plant.
Paulownia has many flowers rich in nectar. The honey made of its flowers is light, transparent, very clear and fragrant. Its color and consistence can be compared only to honey made of acacia. However, it is not only delicious; it may be used for medical purposes too. It is especially useful for upper air passages, lungs and digestive system diseases.
The flowers are used as a decoction or as syrup.
The flowers of Paulownia can be used to heal bronchitis, stomach, cholecyst and spleen diseases. Recently, the flowers found their application in cosmetics industry for perfume production.
It is possible to cultivate Paulownia with other crops (intercropping), especially during the first 2-3 years. Wheat, corn, soybeans, peas, beans, barley, cotton, vegetables and herbs can be farmed between the rows of Paulownia. A farmer can receive double income both from the crops grown between the trees, and from the trees themselves. The trees provide good microclimate for growing co-cultures and increase their productivity. Leaves and flowers of Paulownia are rich in nutrients and it appears to be both cheap and useful source of nitrogen, which enriches the chemical composition and structure of the soil.
Seedlings selection. Paulownia seedlings bred in vitro have to be adapted to daylight illumination and temperature difference for 10-15 days before transplanting to open ground. In case of seedlings, which are already adapted in hothouse conditions, they can be transplanted right away. The larger plants – the better, because tall plants are less likely to be destroyed by rodents or other negative factors. Ideally, Paulownia fields must be protected from rodents, birds, livestock and other bio factors. Alternatively, already wintered saplings 0.5 meters tall can be transplanted.
Lot selection. The tree is quite unpretentious: soil should be only easily permeable to water and air, and shouldn’t be clayey. The soil layer must be at least 1.5 meters thick. Stones, even big ones, are not the problem. Rocky layer shouldn’t be right under the tree. Paulownia isn’t tolerant to acid soils: its pH optimum is above 5.5.
Paulownia also isn’t tolerant to high subterranean waters, the level of which should not be higher than 1.5 meters. Regular and sufficient irrigation is necessary for young plants. Drip irrigation during the first two years causes the best growth rate!
After the lot has been selected, it must be ploughed up. In case of using a drill 60 centimeters in diameter and when 60-100 centimeters deep pits are being dug, ploughing is not necessary.
Saplings of Paulownia can be transplanted from the beginning of November till the end of April. Seedlings of Paulownia are usually planted from the end of April until the beginning of August.
When planning a plantation, it is necessary to keep in mind, that the field has to be passable for farming machines such as tractors, croppers, spraying machines, etc. Saplings landing charts depend on the purpose of the plantation.
If you cultivate Paulownia on a limited scheme the maximum profit would be 3×3 meters. This is: 1050 saplings per 1 hectare. On the fourth year you’ll have to cut off some trees chequer-wise so that they wouldn’t hinder each other. As a result of that, in another four years period, half of the trees in your forest would be eight-year-old and another half – four-year-old (the trees cut on the fourth year would regenerate). At that time you should cut off the eight-year-olds, etc. This is how you start to collect eight-year-old trees every four years. The only disadvantage of this scheme is that you have to be very careful not to damage adjacent trees when cutting plants chequer-wise. This slows the process considerably.
When trees are grown for bio mass according to the 2×0.5 or 1×1 meters scheme, there must be about 10 000 saplings planted per 1 hectare.
One of the most important factors for maximum growth and development of Paulownia is regular watering during the first two years. Once the root system reaches aquifers (usually on the third year of development), there is no need for watering any more. The most effective way of watering is drip irrigation. However, if there is no such possibility, use the furrow irrigation. One sapling requires 1-2 watering per week with about 50 liters of water in total.
In case of growing the trees for timber, straight trunk could be obtained by careful removal of unwanted suckers, and leaving the growing leaves at the same time. This leads to the growing of tall and slender trees.
While the plants are still small, weeds are a threat to the development of young paulownia. Cereal weeds can be controlled with herbicides, but it is necessary to remove foliar weeds manually. It is useful to spud young plants within a radius of 30-40cm.