Paulownia belongs to the monogeneric Paulowniaceae family and is related to and sometimes included in the Scrophulariaceae family. An Asian native growing in China, Taiwan, Vietnam, Cambodia, Laos, Korea and Japan. The Chinese name in pinyin is pàotóng, In Japan the Paulownia tomentosa is kiri. Paulownia is renowned for its extremely fast growth, clusters of showy fragrant flowers and enormous leaves. Wood from the tree is used to make traditional products, furniture, gift boxes, bowls, toys, clogs, handicrafts, musical instruments, plywood and veneer.
Paulownia are summer-growing and winter deciduous in temperate zones. They are medium sized and wide spreading, with large, dark green, downy leaves, occasionally exceeding 60 cm in both length and width. Paulownia trees can grow extremely rapidly in their first few years, after which growth rates slow. As they mature, their leaves become smaller and the crowns, sparse. The leaves can provide useful fodder for stock, and the flowers, which bloom in spring, before the leaves emerge, produce large amounts of nectar.
In China the Paulownia species that are distributed north of the Yangtze River (temperate zone) are P. elongata, P. catalpifolia, and P. tomentosa. P. elongata is suitable to intercropping with crops and grows faster, while P. catalpifolia, and P. tomentosa. grow slower but have better wood quality.
The species that are distributed south of the Yangtze River (subtropical zone) are P. fortunei, P. australis, P. albiphloea, P. fargesii, P. kawakamii and P. taiwaniana. P. fortunei has the characters of fast growth, straight trunk and high wood quality, while P. kawakamii grow's slower with a poor trunk and from, P. fargesii can grow at elevation of 1,200-2,000 meters.
The distribution range of paulownia in China is extremely wide, with its distribution north from Liaoning (south to Xiongyue) to Beijing, Taiyuan, Yan'an and Pingliang, down south from Guangdong, Guangxi and south Yunnan, east to Taiwan and other coastal provinces and west to Minshan Mountain, in Gansu and Gongshan Mountains in Gaoli Yunnan, from the latitude 20° to 40° and the longitude of from 98° to 125° that covers 23 provinces, autonomous regions and municipalities.
The ecological conditions vary so much among the distribution areas with annual mean temperature from 10°c to 22°c. The best temperature range for paulownia growth is from 24°c to 29°c. The lowest temperature that paulownia can resist is -20°c for P.tomentosa, -16°c for P.elongata and -13°c for P.fortunei. Paulownia can adapt to wide-ranged precipitation from 500mm to 2,500 mm. The soil conditions for good paulownia growth are fertile sandy loam to heavy loam soil with with thick soil layer, loose structure and salt content less than 0.05%, pH value from 5 to 8 and underground water level below 2.5m.
The timber is very light (about 300 kg/m3) and is unsuitable for structural use. However, some denser paulownia wood from large, old trees is highly valued in Japan for furniture making. The highest prices are paid for slow-grown yellowish timber with numerous regular, close-spaced annual growth rings.
Features of paulownia timber
• Pale yellow to pale red, odourless, with straight grain and an attractive finish.
• Air dries quickly, but is susceptible to sap staining moulds while drying.
• High strength to weight ratio.
• Low shrinkage coefficient. Rarely warps, cracks or deforms.
• Easy to work, but soft and easily dented and marked.
• Good thermal and electrical insulation.
Characteristics of paulownia
There are nine recognised species of paulownia, within which there are numerous different provenances, as well as a range of hybrids. All are native to China and its neighbours. The two species most often cultivated in China are Paulownia fortunei from the humid sub-tropics south of the Yangtze River, and P. elongata from warm temperate areas north of the Yangtze River. All nine species are available in Australia.
Paulownias have been cultivated in China for at least 2000 years.
In recent decades, agroforestry plantings have increased in China, to shelter crops and provide firewood and timber. It is estimated that 2.5 million hectares of Chinese farm land now has paulownia shelter belts planted on it, from which up to 10 million cubic metres of logs may be produced each year.
Within Asia, paulownia is grown in Taiwan, Vietnam, Cambodia, Laos, Korea and Japan. Elsewhere, paulownia is grown commercially in South America and the United States, where it has naturalised in Appalachian forests. Commercial development has been attempted in Australia, New Zealand and South Africa.
Commercial potential in Australia
Paulownia has been promoted as a tree suitable for farm forestry in Australia. So far, Australian experience is limited and little or no formal trials have been carried out. Since there is little reliable information about many aspects of its cultivation, it remains experimental. Some land owners in Australia are growing small areas, and several large plantations have been established.
• Paulownia can grow quickly, with harvest potential after 10 years.
• Its timber has a high value in export markets.
• Paulownia may replace imported rainforest timber in the local market.
• Growers may receive high returns.
• Many small and large scale plantings have failed.
• Paulownia is not suited to a climate with hot, dry summers and may struggle to survive.
• Horticulture may be more profitable on the high quality sites required for successful paulownia growth.
• Little local growth data is available, especially for trees older than five years.
• Logs which receive high prices in Japan are from slow-grown trees, usually 35 years of age or older. Young, rapidly grown timber has a much lower value.
• Current export markets are very small, while the potential supply from China is large.
• There is no established market for paulownia timber in Australia. It will not threaten imported timbers such as meranti until a large and continuous supply of timber of consistent quality is available.
• Other tree species can be grown more easily and reliably on a wider range of sites to produce timber products for existing markets.
Producers of paulownia plants warn that careful site selection and good management are essential. Growing it without adequate water and nutrients, or without careful and detailed management, is likely to result in failure.
Producing plantation-grown paulownia is a relatively new enterprise in the Australia. The only existing markets are in Japan. Much uncertainty exists concerning its growth characteristics on a wide variety of soils and climatic conditions. However, intensive cultural practices in the early years and proper density control through planned thinnings could yield very high returns for the serious producer.
To be a Successful Paulownia Producer:
1.Select your planting site carefully.
2.Produce or acquire high quality planting stock.
3.Ensure that the planting is done correctly.
4.Maintain competition control for a least 3 years.
5.Follow the recommended coppicing and pruning procedures.
6.Refer to "Paulownia Plantation Management".
7.Work with forester for technical help.
About the Author
Jeremy Wozniak has been working with paulownia since 1982.
Over past 25 years he has conducted field tests of paulownia, in farm land and other places. He has studied Plantation forest astblishment and Management, seed storage, greenhouse and nursery propagation methods. He has worked directly with growers and is in touch with people all over the Australia who grow paulownia.
His involvement in paulownia Forestry research since 1982 has included developing techniques for properagation and Paulownia Plantation Management. He has helped landowners in Australia to produce paulownia trees for plantation culture.
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Silviculture Cultivation Methods
This document contains information for the paulownia grower on site selection, seed collection and storage, root cuting propagation, planting stock, plantation development and early care. Specific information on spacing and growth characteristics necessary for the production of high quality logs.