Paulownia tomentosa, foxglove tree, karri tree, princess tree

Paulownia tomentosa, commonly names princess tree, empress tree, or foxglove tree, is a deciduous hardwood tree in the Scrophulariaceae (Figwort family). The plant is native to China and is widely distributed in central and northern regions, especially Shaanxi, Shanxi, Gansu, Henan, Hebei, Shandong, Anhui, Hubei, Jiangsu, and the Liaoning peninsula. It also occurs in Japan and South Korea. It is an extremely fast-growing tree with seeds that disperse readily and is a persistent exotic introduced species in North America, where it has undergone naturalization in large areas of the Eastern US. It has also been introduced to Western and Central Europe and is establishing itself as a naturalized species there as well.

Apart from the Empress tree, it is also known as the Chinese empress tree, foxglove tree, karri tree, karri tree, princess tree, princess tree, royal paulownia, butterfly tree, empress of China, paulownia, paulownia tree, and royal paulownia tree. The generic name Paulownia honors Princess Anna Paulowna (1795-1865), daughter of Czar Paul I of Russia. The specific epithet tomentosa is a Latin word meaning covered in hairs. The tree is harvested from the wild for local use as a medicine, source of materials, and sometimes as food. It is a showy, aggressive ornamental tree that is also grown in plantations for timber production. It has tended to escape from cultivation and invade disturbed areas. It can invade rapidly after disturbances such as fire, construction or floods, and its ability to resprout prolifically allows it to survive fire, cutting, and even bulldozing on building sites.

Empress Tree Facts

Plant Description

Empress tree is a showy, fast-growing, aggressive, large deciduous ornamental tree that normally grows about 50-60 ft. (15.2-18.3 m) tall with a diameter of at least 2 ft. (0.6 m) with an umbrella-shaped crown and spreading branches. Young shoots can grow as much as 8–10 feet in a single year. Roots can be relatively shallow to deep and well developed, apparently depending upon soil conditions. They are typically widely spreading without a strong taproot. Olive brown to dark brown twigs are stout and brittle, markedly flattened at nodes, mostly glabrous except at the tip, around buds, and along upper edges of leaf scars. Lenticels are pale, prominent, and elongated longitudinally. The pith can be chambered or hollow. Terminal leaf buds are absent. Lateral leaf buds are superimposed. Leaf scars are circular. Bark is a smooth and pale yellow to brown with numerous large lenticels when young, becoming rough and grey-brown with age, often with interlaced smooth areas that are often shiny. The smooth brown bark of young branches has prominent white lenticels.

The plant is found growing in deciduous, mixed forests, roadsides, clearings, forest margins, cliffs, steep rocky slopes, riverbanks, and disturbed habitats including fire sites and forests defoliated by pests. The plant prefers moist, freely drained sands, loams or clays on steep slopes or open valleys, and only rarely on saline and alkaline soils. However, fertile farmland is essential for high-production plantations. It tolerates high soil acidity, drought, and low soil fertility, but prefers full sunlight, ample soil moisture, and fertile soil.

Leaves

Large, deciduous leaves are opposite and broadly ovate, acuminate, and cordate in shape. Leaf margins are entire or shallowly lobed and may be toothed on small plants. Leaves of adult trees are 15-40 cm (6-16 in) long and 10-30 cm (4-8 in) wide, though leaves of stump sprouts maybe twice as large. They are arranged opposite along the stem, hairy on both surfaces. Surfaces are pubescent and dull, light-green above, and pale-green and tomentose beneath. Petioles are also hairy and can be sticky when young. Leaves growing off root sprouts have been measured up to 2 ft. (0.6 m) in length. Twigs are stout, brown, and speckled with white dots (lenticels). They can be slightly hairy when young. Lateral leaf scars are somewhat round, becoming darker and sunken. The pith is chambered or sometimes hollow.

Flowers

Large, showy, fragrant blossoms are borne in upright clusters 15-30 cm (6- 12 in) long at the ends of stout, hairy twigs. Corolla is 5 cm (2 in) long, bell-shaped, and pale violet with yellow stripes inside, ending with five round, unequal lobes. Blooms in April-May before the leaves emerge from round, brown, hairy buds formed during the previous summer. Flower buds are hairy and linear, becoming round.

Fruit

Fertile flowers are followed by woody, beaked, egg-shaped capsules that are 1-2 inches. (2.5-5.1 cm) long and 1-1.5 in. (2.5-3.8 cm) wide, borne in terminal clusters. Seed pods are divided into 4 inner compartments that contain as many as 2,000 tiny winged seeds. Fruits are light green in the summer, become dark brown in the winter, and persist in clusters on the tree until the following spring. The capsules split in half during late winter to release up to 2000 tiny winged, wind-borne seeds 0.08-0.12 in. (2-3 mm). One tree is capable of producing twenty million seeds that are easily transported in water or wind.

Origin and Distribution

Empress tree is native to western and central China where historical records describe its medicinal, ornamental, and timber uses as early as the third century B.C. It has been cultivated for centuries in Japan where it is valued in many traditions. It was imported to Europe in the 1830s by the Dutch East India Company and brought to North America a few years later. It has been naturalized in the eastern U.S. for more than 150 years and is also grown on the west coast. USDA hardiness zones 7-10 are most favorable.

Traditional uses and benefits of Empress Tree

• Decoction of the leaves is used to wash foul ulcers and is also said to promote the growth of hair and prevent greying.
• The leaves are also poulticed onto bruises.
• The leaf juice is used in the treatment of warts.
• The flowers are used in the treatment of skin ailments.
• A tincture of the inner bark is used in the treatment of fevers and delirium.
• It is astringent and vermifuge.
• In traditional Chinese medicine for centuries it has been used to treat bronchitis, coughs, asthma, and high blood pressure, and flowers, leaves, and bark are effective in treating chronic? tracheitis.
• In traditional Chinese medicine,  the bark,  fruit,  xylem,  and leaves have been applied to treat or prevent a variety of diseases, such as hemorrhoid, carbuncle, inflammatory bronchitis, gonorrhea, upper respiratory tract infection?, hemorrhoids, parotitis, asthma, traumatic bleeding, erysipelas,  bacteriological diarrhea?, swelling?, bronchopneumonia, enteritis, conjunctivitis, hypertension?, and tonsillitis.
• Empress trees may also have wound-healing properties, as the leaves have been used for the treatment of frostbite and leg ulcers.
• Leaves, fruits, and flowers are  the  most  important plant parts used  in  folk  herbal
• Folk remedies in China use mashed Empress Tree flowers to treat acne vulgaris and the decoction to treat fungal? infection? on the sole of the foot and the skin between toes.
• Flowers are also used in the treatment of first to second-degree pyrosis.

Other Facts

• Wood is used for making boxes, clogs, furniture, musical instruments, etc.
• It is good for posts and beams in construction.
• It is suitable for intercropping with wheat, oilseed rape, and sweet potato, and in the sub-tropics, it may be intercropped with tea and bamboo.
• It can also be used for windbreaks on farmlands, roadsides, or canal banks.
• It is also believed to reduce sulfur dioxide pollution and grow in environments where other trees may suffer leaf loss.
• Wood is used for oil drums, wine, and beer barrels, tea boxes, fruit boxes, grain storage containers, traditional handicrafts, ornaments, agricultural tools, and especially beehives which maintain suitable temperatures resulting in increased honey production.
• It has been used for plywood and particleboard manufacture, and for kitchen utensils such as wooden bowls, plates, and rice steamers.
• Flowers and leaves are traditionally used as fodder for pigs, goats, and rabbits in Sichuan and Hebei.
• It is cultivated as an ornamental tree in parks and gardens.
• It has gained the Royal Horticultural Society’s Award of Garden Merit.
• The wood yields excellent charcoal used for high-class fireworks and gunpowder.
• It is also used for beams and poles.
• The lightweight timber is highly valued in Taiwan and Japan and is suitable for woodwork, musical instruments, sandals, delicate furniture, linings, cabinets, badminton rackets, and also for fishing net floats, boxes and crates.
• In China, it is planted for erosion control and intercropped with wheat.
• Wood and bark are reported to have astringent properties.
• Several species are used for reforestation in Thailand, and their use is being promoted in East Asia.
• The tree was introduced into the Philippines for wood-producing plantations.
• It seems capable of cleaning air polluted with chlorine.

Management/Monitoring

Paulownia tomentosa can be controlled most effectively using an integrated management approach. Cutting or girdling trees with power or manual saws are effective at preventing seed production, but repeated cutting or herbicide treatment is necessary following cutting since Paulownia readily resprouts.

Hand pulling

Young seedlings of Paulownia can be successfully controlled by manual removal. Pulling is easiest following a rain event, as the soil becomes loose. It is important to remove all root fragments as Paulownia can resprout from root fragments.

Cutting and Girdling

Cutting of Paulownia trees is most effective at the onset of flowering. Cutting at ground level can prevent seed production for that year, but cutting alone must be repeated for several years to successfully kill the tree. Girdling results in top-kill of that stem, but may also induce increased resprouts. Cutting and girdling followed immediately by an herbicide application (cut-stump, hack-and squirt) has good rates of efficacy.

Chemical Control

Paulownia can successfully be controlled by herbicides. The most common herbicides used to control Paulownia include glyphosate and triclopyr.

Foliar Spray

Paulownia seedlings can be controlled by using a foliar spray of either glyphosate (2% solution with 0.5% nonionic surfactant) or triclopyr (2% solution with 0.5% nonionic surfactant). These spray herbicides should be applied directly to the leaves and sprayed to wet.

Cut-Stump

Following the cutting of the trees at ground level, glyphosate (25% solution) or triclopyr (50% solution) should be directly applied to the stump. The cut-stump method can be used at all times of the year, as long as the ground is not frozen.

Girdling or Hack-and-Squirt

Immediately following girdling (approximately 15 cm above the ground and the cut should be well into or below the cambium layer) or hacking, directly apply glyphosate (25% solution) or triclopyr (50% solution) into the cut area.

Basal Bark

Apply a mixture of 25% triclopyr and 75% horticultural oil to the basal parts of the tree to a height of 30-38 cm (12-15 in) from the ground. Thorough wetting is necessary for good control, and spray until run-off is noticeable at the ground line. Basal bark applications should not be applied when the ground is frozen.

References