Future Plants by Randy Stewart: Paulownia

Thursday, August 12, 2010

Paulownia

A genus of 6 species of trees which are among the worlds fastest growing. All are native to eastern Asia though some have been planted in temperate to warm regions around the world. They have been cultivated in China for over 3000 years and are valued for their strong but light timber. The fine-grained, soft, warp resistant wood is used for boxes and chests. Timber may produced on plantation trees as early as 5 years and if cut while dormant, harvested trees regenerate from their existing root systems. The leaves are rich in nitrogen and the roots are excellent for preventing soil erosion. The Paulownias roots survive forest fire and will resprout after.
Massive large trees, they can be equally massive underground. One tree had a root spread of 9000 square feet ( 2.8 times the canopy ). Paulownias are very deep rooted trees with a well developed root system.
Paulownias prefer full sun on moist, fertile, well drained soils. Young trees should be protected from excessive wind which damages the massive leaves. Young trees hate competition and the roots should be kept free of weeds and turf. Insect pests and disease problems do not normally occur.
They are propagated either from root cuttings in winter or seed sown either in autumn or spring. The seed is collected from the ovoid woody brown capsules borne in upright clustes during Autumn. The dried seed pods often persist through the winter after having split open to release hundred of seeds.
Most can grow 15 feet in the first year from seed with ideal conditions. They can also grow up to 30 feet in a single year from stump sprouts.
Seed should be soaked for 10 minutes in 104 F ( 40 C ) water then left in water at room temperature for 24 hours. They can also be grown from root cuttings.
Young trees can be pruned back in March to 2 or 3 basal buds to induce vigorous growth of a strong single trunk. Spent flower clusters may be removed from young trees to increase vigor.
In the far northern parts of the range, these trees are sometimes cut back to the ground each winter to be grown as a massive foliage perennial for tropical effect.
Paulownias do grow in the cooler summer climates of western Europe however are much more vigorous in the eastern U.S. and the warmest parts of Ontario, Canada due to their love of hot humid summers. In fact Paulownia tomentosa has shown invasive tendencies naturalizing into the wild from Arkansas to southeast Pennsylvania; south to Louisiana to South Carolina.
Late spring frosts where they occur may damage the flowers however generally not the foliage which is late emerging. Care should be taken mowing around trees as trunk damage can later result in rot.

An interesting website on Paulownia found on internet ( link below )

American Paulownia Association Inc.
http://www.paulowniatrees.org/

Another Intersting Site
http://paulowniatrees.com/html/photos.html

* photos of unknown internet source

* videos found on Youtube

Paulownia elongata
A very rapid growing tree known to increase trunk diameter at a rate up to 3.5 inches per year. It is among the worlds fastest growing trees and is used for reforestation and timber plantations in the U.S. and China. Also valuable for biofuel production. Some records include: 1st year - 15 feet; 5 years - 37 x 20 feet with a trunk diameter of 9 inches; 13 years - 60 x 37 feet with a trunk diameter of 2.7 feet; 19 years - 60 feet with a trunk diameter of 3.5 feet; largest on record - 75+ feet.
The foliage is very large and the flowers are light purple.
Hardy zones 7+. Similar in appearance to Paulownia tomentosa.

Paulownia fargesii ( Sichuan Paulownia )
A large tree common at elevations of 4000 to 7500 feet in western China where it is native. Some records include: 5 years - 37 feet with a trunk diameter of 7 inches; 11 years - 70 feet with a trunk diameter of 2.5 feet; 31 years - trunk diameter of 3.5 feet; 75 years - 170 feet with a trunk diameter of 7 feet; largest on record - . the growth occurs at temperatures above 46 F from June to September.
The flowers, up to 4 inches in length are white to violet though usually lilac and having golden anthers. They are borne in clusters up to 18 x 12 inches in size during mid to late spring before the foliage emerges.
Hardy zones 6 to 10

Paulownia fortunei ( White-Flowered Paulownia )
A straight trunked, rounded large tree native to China south of the Yangtze river delta. Some records include: 1.5 years - 27 feet with a trunk diameter of 3 inches ( stump sprout ); 4 years - 23 feet with a trunk diameter of 7 inches; 5 years - trunk diameter of 13 inches; 6 years - 37 feet; 10 years - 52 feet; 15 years - 75 feet; largest on record - 170 x 70 feet with a trunk diameter of 7 feet.
The leaves are up to 10 x 7 inches.
The fragrant, white to soft violet flowers, up to 4 x 3 inches are borne in upright terminal panicles in spring before the foliage emerges. The flowers are the largest of any Paulownia and are often spotted within.
The bark is gray-brown.
Hardy zone 6 to 10, requiring hot summers to thrive.

Paulownia glabrata
Some records include: 5 years - 27 feet with a trunk diameter of 5 inches; largest on record -

Paulownia kawakamii ( Taiwan Paulownia )
Also called Sapphire Dragon Tree. A sturdy, erect large tree native to Taiwan and less commonly neighboring parts of China. It is critically endangered due to habitat loss in the wild. Some records include: fastest recorded growth rate - 16 feet; 11 years - 33 feet with a trunk diameter of 9 inches; 21 years - 40 feet with a trunk diameter of 16 inches ( average ); largest on record - 66 x 60 feet ( larger trees likely exist ).
The heart shaped leaves borne on the stems in pairs are huge, reaching over 12 inches, even up to 24 x 24 inches on vigorous shoots.
The flowers, up to 2 inches in length, are pale purple and white, borne in terminal clusters.
Hardy zone 6 to 9

* video found on Youtube

Paulownia tomentosa ( Royal Paulownia )
Also called Empress Tree, Princess Tree & Hairy Paulownia. A large broadly columnar tree native to north and central China, Korea and Japan. Some records include: fastest recorded growth rate ( non stump sprout ) - 20 feet; 1st year - 13 feet ( from seed ); 1st year - 27 feet ( from root cutting ); 2 years - 23 feet; 3 years - 35 feet; 5 years - 37 x 20 feet with a trunk diameter of 14 inches; 11 years - 70 feet with a trunk diameter of 30 inches; 18 years - 40 inch trunk diameter; 20 years - 82 x 82 feet; largest on record - 170 x 70 feet with a trunk diameter of 7.6 feet. Longest lived - 200 + years ( typical lifespan is over 80 years ). The Paulownia's large leaves cast a dense shade.
The sometimes lightly lobed, taper pointed heart shaped leaves are up to 12 x 12 inches on older trees, up to 40 x 36 inches in length on young vigorous shoots. The downy foliage is bright green at first, turning to deep green in summer then to yellow-brown in autumn.
The trumpet shaped, foxglove-like flowers, up to 3 inches in length are violet-blue outside, yellow inside. Up to 50 to 60 flowers are borne in the upright terminal panicles in mid to late spring before the foliage emerges.
The curved, stout twigs are light gray.
The bark has shallow orangish furrows and broad greenish-gray ridges.
Hardy zone 6 to 10 as a tree ( tolerating -12 F to 106 F ). It is root hardy in zones 4 and 5 and is even known to be grown as a massive foliage perennial as far north as Montreal where it reaches up to 12 feet in a season. Young trees in zone 6 should be protected from winter winds though are fully hardy once established.
Tolerant of salt, pollution and poor soil. Royal Paulownia is NOT tolerant of swampy sites and can be killed by as few as 3 days of flooding during the growing season.

* photo taken on March 1994 @ Longwood Gardens near Philly, PA