Paulownia leafy tree or the Princess' tree, also nicknamed "aluminum wood" for its strength, is a tree with a broad crown, thick stems with big leaves and lilac, fragrant flowers. Inflorescences grow in autumn and turn into blossom in May-June. Its fruits look like 3-4 cm brown capsules and are very decorative. This exotic tree stands out with its abundant flowering in early spring, before turning green. It's the time when large lilac-colored corollas open up in shapes quite like the snapdragon. These flowers look very appealing to the bees, its honey production being more fruitful than acacia's. Paulownia trees are drought resistant once their roots fix them deep into the earth, in search of water, rather than at the surface. This allows easy usage around the tree trunk and favors neighboring alleys or other facilities. Its shade is beneficial in summer, but in winter it becomes leafless and lets the sunlight reach through. Unlike other fast growing trees that have a short lifespan, a healthy Paulownia tree can last for 80 to 100 years. Paulownia is a tree with falling leaves, a very high growth rate in favorable conditions and a short rotation cycle.
Its spread varies from tropical to temperate clime, in places with varying rainfall average. It may be found at altitudes starting near sea level and up to about 2400 m. There are nine species of Paulownia, which are similar in terms of appearance and properties of wood mass. They were developed scientifically in order to determine acclimatization to the environment.
Paulownia tree can tolerate a wide range of environmental conditions. To ensure maximum growth, irrigation may be needed throughout the development cycle. Paulownia also tolerates a wide range of soil types; nevertheless, the ones necessary for optimal growth are the deep and fertile soils. Loose sandy or clay soils are to be preferred. Plantations should be well drained, as paulownia will not tolerate flooded soils. Trees will defoliate and may even die after the land was flooded for a short period of 3-5 days. Therefore, the places where the groundwater level is less than 1.5 m from the surface are not suitable for paulownia. Salty soil and water may also affect growth. In general, Paulownia will not tolerate low levels of light, growing best in direct sunlight. In order to obtain optimum height and diameter, an average daily temperature of about 24-29ºC is required. Paulownia trees' resistance to cold varies; among its species, Paulownia Europe is capable to withstand temperatures up to -30ºC, but stops growing below -20ºC. Harsh spring frosts can destroy growing shoots or can damage tree branches, affecting their growth and form. Paulownia needs sheltered areas from persistent winds that can cause permanent trunks bending, turning them unusable as saw logs. Strong winds can damage or even break living trees. Young cuttings have very large leaves which are more sensitive to frost wind or hail damage
Paulownia require intensive management where when grown for timber production. In order to get a high price for the timber you need to have large diameter snubless logs. Tree pruning is essential for maximizing the amount of snubless logs, but may have a slightly negative impact on growth. Losing the master shoot is a common problem and correcting pruning is required in order to maintain the trunk straight. Paulownia will not tolerate abundant grass when very fast growth is envisaged and therefore a firm control is requires in the early years of growth. Paulownia grows very well from underwood. If the original plants are weak or have a deformed main stem, shortening off to ground level can allow one a straight stem to become a complete cutting.
The color of the wood is light yellow to bright red. Timber has a density of 300-330 kg/m3 and 15% moisture content, with the fiber straight and is odorless. Although it is lightweight and has a low density, it is relatively resistant in terms of specific gravity. The wood has excellent thermal and electrical insulation properties and is easy to air dry. It can be used without restrictions in construction works, demonstrating excellent properties for supporting poles, rafters, etc. As wood material, Paulownia presents excellent characteristics, being easy to smooth, saw or carve. The wood material that is soft is exposed to surface damages and requires careful handling during production and use. As wood material, Paulownia tends to form points with the resin, followed by grinding while still green and the surface may get discolored.
Timber dries well, with no easy distortion, cracking or change of shape. A plate of 25 mm thickness can be dried up to 10% moisture in 25 days, at normal room temperature. After drying, timber is very stable.
- The market of paulownia wood material, although at its beginning, shows a tendency of development in Romania. Paulownia wood material can be used in making various articles.
- packing boxes,
- safe deposit boxes,
- joints and
Paulownia weighs 1/3 of the oak's weight and half of the pine's.
Paulownia has been tested and proved to be the most resistant of all the types of trees in the world when related to weight - and this is why it is called aluminum wood. Paulownia can be cut thinner and still provide about the same strength and weight. Paulownia offers a benefit in terms of space saving and can be cut to half thickness. There are also significant cost savings as about half of the material should be purchased. Paulownia is well preserving nails and screws and requires no pilot holes for drilling. In fact, both the yellow poplar and the white pine were found to cleave sooner than Paulownia. Flat head screws can be made leveled with the surface. Grown as plantation, Paulownia is typically snubless.
Paulownia has been used extensively in the Orient for more than 1000 years for high quality furniture, musical instruments, carvings and decorative finishes. It can be peeled for veneer. Complex models may be cut with a mechanic jigsaw or bandsaw without easy splitting. Paulownia was the favorite wood of many sculptors from Asia and America. One can make pieces of furniture, doors and windows against tight tolerances. All usual finishing materials may be applied on and stuck up well with adhesives.
Air drying takes less than 30 days. Plywood can be dried in the oven, at high temperature, in less than 24 hours, from 10% to 12% moisture content and no shrinkage. Decrease reported from green to oven drying is only 2.2% radial and 4.0% tangential. Paulownia remains stable during changes in humidity and suffers little decreases or dilatations as compared to most of other types of wood. It is very durable and resists to breakdown under lack of contact with the ground. This wood is insects proof-fast.
Paulownia is a very good insulator. Houses made of Paulownia logs are considered to have twice the R factor, as compared with pine and oak logs. This resistance to temperature gives this wood a greater non-inflammability. Ignition temperature is of about 400°C, which is almost double than for many conventional American hard and softwood trees.
Paulownias are fast growing trees and have a light blonde look, much like white ash. They are beautifully colored, with a variety of shades and can be made to imitate other wood materials. After planing, a silky luster is revealed. The touch sensation is also highly silky.
Hemicellulose Pentosan 22, up to 25%. Cellulose, 46 to 49%. Lignin, 21 to 23%. Water, 7 to 8%. Ash. 50, up to 1.1% Fiber, 58.5 up to 60.1%