Notes to broadcasters
There are nine species of the paulownia tree which is native to China: Paulownia fortunei, Paulownia albiphloea, Paulownia catalpifolia, Paulownia elongata, Paulownia australis, Paulownia fargesii, Paulownia kawakamii, Paulownia tomentosa, and Paulownia taiwaniana. The tree has grey, brown, or black bark which is smooth and porous when young. As it gets older the bark develops vertical cracks. The crown of paulownia is the shape of an umbrella, with sparse branches and leaves that let the light through. The leaves appear late and remain late in the growing season. In young trees the leaves are large with long stems and serrated edges. Leaves of mature trees are smaller with a smooth or wavy edge. Paulownia can reach a height of 10 to 18 metres and can grow up to 2½ metres in one year under ideal conditions.
Paulownia can be propagated by seed, root cuttings, or by stem cuttings. Most people use root cuttings from trees that are 1-2 years old, or from mature trees. Trees propagated by this method grow rapidly and uniformly, are easy to manage, and have a high survival rate. Trees grown from seed do almost as well as trees grown from root cuttings and have the added advantage of being more genetically diverse and therefore more able to resist diseases.
Paulownia trees grow well in many conditions. They grow in mountains or on flatlands, and adapt to many soil types, especially the humus rich clay subtropical soils. They also grow in the red soils of the tropics and on dry steppes.
Paulownia can grow in a variety of climates. The ideal daily temperature for paulownia is 24 °C to 29 °C, although some species can grow in temperatures as low as 20 °C. Paulownia’s need for water varies greatly, from as low as 500 millimetres a year to a maximum of 2000 or 3000 millimetres a year.
Weed control is important for survival and growth of paulownia. Also, it is important to water very well in the early stages of growth so that the roots penetrate deep into the soil.
Farmers use the branches, the leaves, and the flowers. Over 10 years, one paulownia tree can produce as much as 300 to 400 kilograms of branches for firewood. The leaves, flowers, wood, and fruit all have medicinal properties.
Paulownia trees are often used for landscaping and reforestation. They are also used for planting in urban and industrial areas, and for the recovery of lands stripped bare by mining since the trees can grow in a wide range of soil acidity and the tree leaves resist atmospheric pollution.
In China, paulownia trees are being used successfully in agroforestry projects and for intercropping with agricultural crops on close to 2 million hectares of farmland.
This information is adapted from Paulownia in China: cultivation and utilization, 1986, 65 pages, by the Chinese Academy of Forestry staff. Asian Network for Biological Sciences, and IDRC.
By growing trees with crops you can increase crop yields and harvest lumber, firewood, and livestock feed at the same time. In different parts of the world farmers are experimenting with different combinations of crops and trees. This is called intercropping.
Intercropping is growing different crops together in the same field. For example, you might plant corn in one row, beans in the next, and corn again in the next. This way you make better use of soil nutrients and harvest two crops instead of one.
You can also intercrop crops with trees. It is important to choose trees that are well adapted to local conditions and if possible, to use a variety of trees on your farm.
In China, farmers increase yields by planting paulownia trees (Paulownia spp.) with grain crops such as corn, wheat, or millet. They space the trees in rows 5 metres apart with 30-50 metres between rows. This way they can plant 40 to 67 trees per hectare. In this system the farmers consider the food crop to be more important than the wood harvest.
Grain crops have a higher yield because trees can improve the climate around the crops. Trees reduce the damaging effect of dry winds and put moisture into the air. Trees also help to save soil.
The paulownia tree grows quickly. The Chinese people say that it looks like a pole after one year, like an umbrella at three years, and, after five or six years, it can be sawed down and cut into small boards. The branches can be used for fuelwood. A 10 year old tree produces 400 kilograms of branches per year. The roots go so deep into the soil that they do not compete with other crops for water and nutrients. In fact, paulownia roots can absorb water and nutrients deep in the soil that other plant roots cannot reach. This is useful especially during the dry season when paulownia absorbs the underground water and releases it into the air.
Paulownia is a useful tree in other ways too. The wood is lightweight yet strong. It dries easily. It has a beautiful grain and it does not crack or warp. It is easy to work with and is excellent for making musical instruments, furniture, and plywood.
The leaves and the flowers are good fodder for livestock because they are rich in protein, carbohydrates, and minerals. A ten year old tree produces 30 kilograms of fresh leaves each year. The leaves can also be dug into the soil as green manure.
Sweet potatoes and sesame seeds do not grow well with paulownia. Yields of these crops tend to decrease particularly when intercropped with trees more than five years old.
Generally, however, the Chinese farmers harvest more food when they grow trees with crops. They also harvest valuable livestock feed. And within ten to fifteen years they are harvesting enough lumber to produce an important extra income.
This is one example of how farmers grow trees to improve crops. There may be trees that farmers use to improve crops in your region.
- This script is based on “Using paulownia trees for intercropping”, pages 48 50 in 101 Technologies from the South for the South, 1992, published and available free of charge in English and French from the International Development Research Centre (IDRC), P.O. Box 8500, Ottawa, Canada K1G 3H9. This booklet features technological innovations in agriculture, forestry, energy, and health that were developed in the south and researched with funds from IDRC. The production of this script and others from 101 Technologies was funded by IDRC.
- This script was written by Max Lizano, Agronomist, Kingston, Ontario, Canada. It was reviewed by Michael Gold, Professor, Agroforestry Department, Michigan State University, U.S.A. and Peter Beckjord, National Paulownia Center, Beltsville, Maryland, U.S.A.
- Paulownia in China: cultivation and utilization, by the Chinese Academy of Forestry Staff, 1986, 65 pages. Asian Network for Biological Sciences and International Development Research Centre.
- Agroforestry in China, 1991, 216 pages. Chinese Academy of Forestry and IDRC.
- Paulownia in China, a film produced by Agricultural Studies of China. English, 27 minutes. Paulownia Research Group, Forest Research Institute, Chinese Academy of Forestry. Wan Shou Shan, Beijing 100091, People’s Republic of China. Paulownia seeds available.
- “Paulownia, the tree of choice in China”, Vol 4, No. 1, 1991, (p. 1), International Ag sieve. Rodale Institute, 222 Main St., Emmaus, Pennsylvania, 18098, U.S.A.
- How to grow paulownia, John F. Kundt, 1987 88, Bulletin No. 319, University of Maryland, Co op Extension Service, Beltsville, Maryland.
- Paulownia tomentosa: an excellent tree for agroforestry and windbreaks in the more temperate regions of the developing countries, Michael D. Benge, 1987, 165 pages. Bureau for Science and Technology, Office of Forestry, Environment, and Natural Resources, Agency for International Development, Washington D.C., 20523, U.S.A.
- National Paulownia Center, c/o Dr. Peter Beckjord, 10908 Dresden Dr., Beltsville, Maryland. A small package of seeds with growing instructions, and a newsletter, are available at no cost, although they would appreciate receiving US$1.00 to cover mailing costs. A VHS video (68 minutes) is also available.
- Intercropping: Tree A with food crop B. Note the tree roots deeper than the food crop roots. Food crops must be somewhat shade tolerant. Graphic: Peter Beckjord