How and Where to Plant Paulownia?
Recommendations for Starting Your Paulownia Cultivation
You may have heard about the impressive characteristics of the tree of the future and are now eager to start planting Paulownias. But hold on; to ensure the success of your planting, check out the tips below to choose the right land, prepare it, and properly plant your Japanese Kiri seedlings.
**Choosing the Right Location:**
1. Temperature
The Paulownia tree, or Japanese Kiri, is found in subtropical, tropical, and temperate regions. Paulownia can adapt to a wide range of temperatures, but optimal growth is suggested to be between 24-33ºC.
Planting should generally take place in spring and autumn to avoid frost that can damage the cellular structure of leaves after the first buds emerge. Young trees tend to be more sensitive to low temperatures during the first two years of cultivation.
2. Altitude
Paulownia species can grow in areas up to 2,000 meters in altitude, but their growth is more pronounced in lands positioned between 700 and 800 meters.
3. Soil Characteristics
The Japanese Kiri is a highly adaptable species that grows well in many types of soil. The most suitable and recommended soils are light, well-drained, and sandy.
Soils with over 30% clay and porosity below 50% are not recommended for Paulownia. Very compact, heavy, rocky, clayey soils that are prone to flooding will likely hinder the trees' development.
Another important factor is salinity. The Japanese Kiri does not tolerate salinity above 1%.
4. Soil Depth
Deep, well-drained soils are most recommended. The soil layer should be at least 2 meters deep to provide enough space for the root system to develop, but 5 meters would be ideal.
5. Soil pH
Soils with a pH of 5.0 to 8.0 are best for the development of Paulownia tree.
6. Topography
Paulownia can be cultivated on steep slopes, but this obviously increases operational costs (irrigation, maintenance, and harvesting). Additionally, the trunk shape can be affected by uneven sunlight and strong winds, which may result in inferior wood quality.
7. Precipitation
A rainfall index of at least 800 mm/year is recommended for good growth of Japanese Kiri cultivation. Otherwise, the plantation should be equipped with an irrigation system.
8. Wind
Areas with winds above 45 km/h should be avoided for planting Paulownia. Winds up to 30 km/h are not ideal, but this can be mitigated by installing stabilizers during the first year of development until a strong wooden stem is formed.
9. Sunlight Incidence
Paulownia requires a lot of sunlight for optimal growth. Although it is a fast-growing tree, it is very thermophilic and does not like competition for light during its early life stages. For this reason, a spacing of 4x4 or 5x5 is recommended.
10. Humidity
High humidity increases the risk of microbial pathogens (especially fungi). Therefore, Paulownia planting should ideally be done in a sheltered area, with low wind speed and a low risk of summer storms.
11. Easy Access
When choosing the land, consider access for tractors, trucks, and agricultural machinery. The volume of harvested wood is significant; one hectare can represent six truckloads.
12. Legal Registration
The plantation location must not be situated in a protected area (animal sanctuary, national park, natural forest, etc.). It is advisable to check the legality of your planting with the relevant authorities in your region.
Now that you know where to plant Paulownia, let’s move on to tips for preparing the land.
Preparing the Land:
13. Tilling the Soil
Before planting, it is recommended to till the soil at least 40-60 cm deep to allow greater oxygen introduction into the soil and to remove the roots of weeds and perennial shrubs. If the soil is heavy and clayey, the trenches should be 70-80 cm deep.
If selecting pasture areas for planting Paulownia, the soil should be worked at least 4 to 5 weeks before planting. The land should be cleaned before planting, and any weed regrowth should be strictly controlled.
14. Leveling the Land
The land needs to be leveled once or twice. After that, we can consider the land prepared for furrowing, marking, and finally planting.
15. Furrows
The furrows should be made to a depth of 20 cm. It is advisable to mix manure into the soil beforehand in the furrows where the Japanese Kiri seedlings will be planted.
The tree should be planted in such a way that the trunk is fully exposed, leveling with the soil. During winter, it is recommended to build a mound of manure to raise the soil level at the planting site. The mound should be 25-30 cm higher than the ground.
16. Fertilization
Based on the results of soil analysis, it may be necessary to fertilize the soil at the time of planting.
If a preliminary soil analysis has not been conducted, it is advisable to fertilize the soil with:
- Organic fertilizer - 1:1
- Triple superphosphate (TSP) 200 g
- Potassium phosphate – 120 g
- Ammonium nitrate – 150 g
This fertilization program is not mandatory; however, an annual addition of manure is strongly recommended.
Planting Paulownia in monoculture depletes the soil, and you should keep this in mind. For this reason, additional fertilizers are necessary at certain times. After the first cut of the Paulownia trees, for example, it is recommended to monitor the levels of nitrogen, potassium, and phosphorus in the soil.
17. Irrigation
Water with 5 liters per plant at the time of planting if the soil is dry. If the soil is moist, there is no need to water.
Normally, 3,500 m³ of water per hectare is sufficient for optimal growth. During the first two months, the seedlings should receive between 7 and 10 liters of water per day.
For optimal growth during the first months of development, it is essential to water with 20 liters per plant weekly. The watering can be split into two equal applications. Insufficient watering delays growth but does not kill the tree. A well-designed irrigation system can increase yield by up to 30%.
Soil and air moisture are very important for Paulownia cultivation. An additional watering is recommended if annual precipitation falls below 150 mm per month. Watering is necessary in subsequent years if monthly precipitation is below 50 mm.
It is important to note that water with very high salinity will prevent the tree from effectively absorbing nutrients.
Land Prepared! Let’s move on to the steps on how to plant Paulownia Tree:
18. Seedling Selection
If the goal is to produce Paulownia wood with good mechanical properties and appearance, then we need to obtain long, straight trunks without knots. Each variety has a well-defined morphology, with Paulownia often classified by the shape of its crown: dense and wide (Paulownia Tomentosa), semi-wide (Paulownia Elongata), narrow (Paulownia Fortunei), and some of its hybrids.
Here at Paulownia Brasil, we recommend the hybrid between the species Paulownia tomentosa and Paulownia fortunei, which has adapted very well to different plantings in Brazil. To purchase Paulownia seedlings, click here.
19. Spacing Between Paulownias
The ideal planting scheme is 5x5 meters or 5x4 meters between the trees.
This means between 400 and 500 trees per hectare.
20. Consortium of Paulownia with Other Crops
Annual vegetables, such as peas and beans, can be grown between Kiris with little detriment to the trees in terms of water and nutrient loss. Even when they decompose at the end of the season, they enrich the soil with nitrogen.
21. Threats to Paulownia Cultivation
Like other species, Paulownia seedlings should also be well protected from herbivorous animals.
As mentioned earlier, Paulownia should not be planted in areas prone to flooding, strong winds, and low sunlight incidence.
22. Pruning
Any shoots that emerge from the trunk just above the large leaves should be cut off, but care should be taken not to remove the large leaves directly attached to the trunk.
The leaves of Paulownia are the trees' solar panels—they capture sunlight and, in combination with water and nutrients, convert it into growth.
Removing these leaves delays the growth of Paulownia.
Branches not removed during the first year may result in the loss of height growth potential, but they can be removed later without causing significant long-term damage.
For a clean trunk up to five or six meters, it is recommended to prune them within the first three or four years.
However, drastic pruning may inhibit the normal crown formation and even prevent the tree's natural development, resulting in slow trunk diameter growth of Paulownia.
23. Weed Control
Weed control promotes the growth and vitality of the plants. A circle with a diameter of 1.5 m around each tree should be kept free of weeds for at least the first two years. If young stakes appear around the tree, they should be removed manually and not with herb.