The Paulownia tomentosa, also known as or Princess Tree, Empress Tree, and Foxglove-Tree, is a tree species native to East Asia. In recent years, it has started to spread in our country. Interest in this plant belonging to the Lamiales order is growing worldwide due to its excellent environmental and industrial uses. It is, in fact, a rapidly growing tree with valuable wood, capable of absorbing many environmental pollutants.
In this article, we will introduce you to the botanical characteristics of this plant and its primary uses. We will also see how to cultivate a Paulownia tomentosa the right way, using only organic techniques.
The Paulownia Tomentosa Tree
Paulownia tomentosa is a tree of the Lamiales order, in the botanical family Paulowniaceae. In its native Eastern regions (China), it lives in mixed deciduous forests or in large areas dedicated to intensive cultivation.
It arrived in Europe in the early 1800s, imported by the “Dutch East India Company.” The name Paulownia tomentosa comes from the Russian princess Anna Pavlovna, daughter of Tsar Paul I. In the environments where it has been introduced, the plant has a broader spontaneous spread. In Italy, it is present in all regions and is also known by the simple name Paulonia. It is easily found in ruderal environments, such as at the edges of forests, in rocky areas like steep rocky slopes, or along riverbanks. But it is also very easy to find this Empress Tree in urban areas. For example, in the gaps in garden pavements, under retaining walls, in abandoned green areas. In the forest, it is a pioneer species, capable of quickly colonizing areas affected by fires or other extreme situations, such as floods.
Characteristics of the Empress Tree
A peculiar characteristic of Paulownia tomentosa is its fast growth. In just 3 years, the tree can easily exceed 12-15 meters in height. At maturity, it can reach up to 20 meters. The Paulownia plant is majestic, with a very branched crown and a natural, expansive, and elegant posture. It is a deciduous species. In adulthood, its trunk has gray bark with a smooth surface. The wood is light, very lightweight, but equally durable. In its juvenile stage, it develops as an erect and branched stem, full of large leaves.
The plant exhibits distinct leaf dimorphism, with a clear difference between young specimens (with enormous leaves) and adults (with smaller leaves). The leaves of Paulownia tomentosa are green, typically heart-shaped (with a pointed apex and cordate base). They can grow up to 40 cm in length with an equally significant diameter. They have a slight fuzziness, prominent veins, and a strong, penetrating odor. They are found singly and opposite on the stems. Especially in its juvenile form, Paulonia can be confused with plants of the Catalpa genus, particularly the Bignonia catalpa species, which look similar in leaf appearance. However, over the years, the plant stabilizes its growth and reduces the size of its foliage, becoming unmistakable.
Flowers and Seeds of Paulownia Tomentosa
The flowering of Paulownia tomentosa occurs in late spring, between April and May. It is highly conspicuous, making it a perfect ornamental tree, even with a single specimen in the garden. The flower consists of a large pyramidal panicle, which can be up to 50 cm long. It has a short peduncle (1-2 cm) and a calyx about 1.5 cm long with 5 lobes. The corolla measures from 5 to 7 cm, is highly fragrant, bilabiate, and campanulate. The color is a vibrant lilac-violet. In general, the inflorescences are rich in glands containing essential oil. Pollination is entomophilous, meaning it is carried out by bees and other pollinating insects. The flowers produce large amounts of pollen and nectar, making them highly attractive to bees, which can produce excellent unifloral honey. The fruit consists of a bilocular capsule, ovoid and pointed (up to 4.5 cm long). It contains up to two thousand winged seeds, measuring up to 4 mm. An adult Paulownia tomentosa tree can produce up to 20 million seeds in a season. This large number of seeds can be dispersed by the wind over a distance of 10 km, making the plant easily spread, even becoming invasive. The capsule containing the seeds opens between winter and spring. However, the seed will only germinate if it has the right soil and lighting conditions.
How to Cultivate Paulownia Tomentosa
The cultivation of Paulonia can serve various purposes. Naturally, growing a Paulownia tree in the garden for ornamental purposes is different from starting a specialized cultivation to obtain wood or to complement an apiculture business. In the first case, it is very likely that you will find Paulownia tomentosa growing spontaneously in the soil, as it spreads easily. We recommend not considering it a weed and taking care of it like other plants in your plot. For intensive cultivation, cultural precautions are greater, although the hardiness of the Empress Tree is precisely what makes this species very interesting.
How Paulownia Tomentosa Reproduces
Paulownia tomentosa can be reproduced either sexually, from seed, or vegetatively (cuttings). Reproduction from seed is recommended, especially for small cultivations primarily aimed at ornamental use. Seeds are readily available in stores. Direct sowing is carried out in spring, followed by thinning out the young shoots. Cuttings are more suitable for those who want to reproduce the same species as the one already cultivated. For example, it is very common among permaculture practitioners. It is an easy technique to execute. Simply take young shoots from the axils of the branches. The best time is always spring. In intensive Paulownia cultivations, it is preferred to plant plants derived from selected clones. These can be purchased from specialized nurseries and are capable of maximizing yields.
Climate Requirements for Paulownia
Paulownia tomentosa is an extremely adaptable species. It prefers a mild climate and can be cultivated from lowlands to hills, but it also grows well in the mountains. It can withstand both winter cold and long periods of summer drought. If you are cultivating a specialized plantation with selected clones, you will have plants that can grow in a temperature range from -27°C to +48°C. The best position is sunny, but partial shade is also suitable.
Ideal Soil for Empress Tree
Regarding the best agricultural soil for growing Empress Tree, you have a wide choice. The plant thrives in the following types of soil:
- Deep and well-draining soils;
- Soil mixed with small-sized rocks;
- Sandy soil;
- Clayey soil (with 20% clay) that can lead to water stagnation;
- Proximity to saline ponds;
- Soils that are too saline.
The optimal soil pH for Empress Tree cultivation is between 5.5 and 8.
Preparing the Soil
In intensive Paulownia cultivation, the best way to prepare the soil is through ripping (subsoiling) with a ripper. Plowing is only practiced in the most challenging soils.
Planting a Paulownia Tree
Planting Paulownia tomentosa seedlings can be done in the autumn (September/October) or early spring (March/April). Selected clones are usually sold in small plastic pots with a diameter of 10 cm. Therefore, there is no need to dig large holes for planting. However, you should take care not to damage the young root system and risk post-planting mortality.
Plant Spacing for Empress Tree
The distance at which to plant Paulownia trees differs depending on the purpose of cultivation, whether industrial or ornamental. In the first case, the planting distance can be very close, at 4m x 4m. In the second case, you should consider the space in your garden. In any case, it is necessary to leave at least 8m between each tree.
Caring for Paulownia Tomentosa
As emphasized several times, Paulownia tomentosa is a highly robust species and, therefore, requires minimal care. The critical period is immediately after planting when the plant is still establishing its root system. During this time, the soil should always be kept moist to allow the taproot to grow deep. Therefore, both in autumn and spring, you should irrigate the plant if there is no natural precipitation. Throughout its vegetative life, Paulownia tomentosa does not require irrigation. While it benefits from it during the summer, it can survive without it. Fertilization is only necessary in poor soils, especially those depleted by intensive cultivation of other crops. In such cases, well-rotted compost is a good organic fertilizer choice. Alternatively, mature manure can be spread and incorporated into the soil before planting. If needed, annual fertilization with compost or manure should be done between autumn and winter. Applying additional fertilizer to already fertile soil can be counterproductive.
Pruning Paulownia Tomentosa
Pruning Paulownia tomentosa aims to control its vigorous shoot growth. In just one year, shoots can grow up to 5 meters, especially if the plant has developed a robust root system and is in favorable soil conditions. Another factor that promotes shoot growth is shaded exposure. To grow Paulownia tomentosa as a tree, you need to periodically remove the shoots. The best time to do this is in the autumn-winter during the vegetative dormancy. For ornamental Paulownia cultivation, additional pruning may be necessary on the branches to promote air circulation and remove dry or damaged parts.
Technical Pruning of Paulownia Tomentosa
In specialized young plantations growing selected clones of Paulownia tomentosa, a technique called technical pruning is used. This is done on the trunk, regardless of its diameter, in the first winter after planting. For instance, if the plant was put in the ground in autumn (October), the technical pruning should be done in February of the following year. After technical pruning, with favorable temperatures, the plant will begin to produce new shoots. At a height of 50 cm, all but one shoot should be removed, leaving the dominant one as the main stem. The chosen shoot will grow rapidly upward. This operation is also known as coppicing and allows the trunk to develop with minimal branching, growing up to 6-9 meters. This type of pruning results in high-quality timber with minimal knots and few defects. As soon as three years after technical pruning, you can begin total trunk cutting for production purposes. In specialized Paulownia plantations, the trunk is also cut every four years, producing larger-diameter trunks and yielding highly valuable timber.
Protecting Paulownia Tomentosa from Pests
One of the significant advantages of cultivating Paulownia tomentosa is its high resistance to pests and diseases. There are no significant pest problems reported in our country. This resistance may be due to the plant’s ability to attract beneficial insects, making it perfect for creating ecological infrastructure.
Environmental Uses of Paulownia
The growing interest in Paulownia tomentosa is attributed to its environmental uses. With its robust vegetative growth and rapid development, the plant is considered one of the best species globally for carbon dioxide absorption. Another characteristic of Paulownia is its ability to absorb heavy metals, making it useful for soil remediation near industrial or chemical sites. In urban environments, Empress Tree is used along tree-lined streets, as its large foliage in young specimens can absorb fine dust particles. It’s also an ideal species for reforesting areas severely affected by wildfires. In forestry, it’s used to stabilize land prone to landslides and erosion. However, despite all these benefits, the spontaneous spread of Paulownia tomentosa should be kept under control to prevent it from becoming invasive and displacing native species, thereby reducing biodiversity.
Industrial Uses of Paulownia
The cultivation of Paulownia is also interesting for its various commercial, industrial, and agricultural uses. It can be highly profitable in beekeeping, with up to 1000 kg of excellent honey obtained from one hectare of intensive cultivation. Regarding wood uses, this empress tree is known in the furniture industry as “wood aluminum” due to its high malleability. In just a few years, the wood from this tree is ready for use in various applications, including construction, furniture, marine, musical instruments, and finishing. It is known for its clarity and refinement, as well as its high resistance to fire and puncture. Every part of Paulownia tomentosa is utilized; its foliage can be used in livestock farming, and wood waste serves as valuable biomass for clean energy production.