Saturday, November 25, 2006

Paulownia: aka Kiri Tree aka Princess Tree: Heritage and the Future

Invasive Species Weblog, Thursday, November 23, 2006, on Paulownia tomentosa presents land managers and naturalists with a seemingly horrifying scenario: intentional replanting of a known invasive. The references to this plant’s potential to destroy natural areas are extensive. The Plant Conservation Alliance, Alien Plant Working Group notes that (underlining is mine): “Princess tree can be found along roadsides, stream-banks, and forest edges. It tolerates infertile and acid soils and drought conditions. It easily adapts to disturbed habitats, including previously burned areas, forests defoliated by pests (such as the gypsy moth) and landslides and can colonize rocky cliffs and scoured riparian zones where it may compete with rare plants in these marginal habitats. Its ability to sprout prolifically from adventitious buds on stems and roots allows it to survive fire, cutting, and even bulldozing in construction areas.” The adaptability of the species is the threat to native plants which it can out-compete.

Other people would see the species with a different filter, identifying the above stated qualities as positive for short term human endeavors including fodder for livestock, furniture, musical instruments, and quick erosion control, as well as being attractive under current landscape norms. The World Agroforestry Centre posts the following: “Products: Fodder: Leaves make good fodder for pigs, sheep and rabbits. Fibre: Its rapid early growth has attracted the interest of the paper industry. Timber: This species is not grown for its biomass alone, but also for its use as a quality furniture wood, veneer, carving and musical instruments. Services: Shade or shelter: It plays an important service role as a windbreak wherever it grows. Reclamation: In the USA, for instance, it seems well adapted to harsh micro-climates on surface mines and may aid in the reclamation of such sites. Ornamental: its rapid growth, attractive flower, and excellent wood quality make it a genus that needs to be considered for further use in the United States. Intercropping: The roots occupy a different layer than most annual crops and this suggests its potential for intercropping. However when propagated by cutting, the tree forms an extensive lateral root system and loses its deep rooting characteristics.” © ICRAF Copyright

In addition, we find from Invasive species fact sheet prepared by:
Ann F. Rhoads and Timothy A. Block. Morris Arboretum of the University of Pennsylvania, 100 Northwestern Ave., Philadelphia, PA 19118
April 2002: (underlining is mine) “EFFECTS OF INVASION Empress-tree appears to be limited to edges or openings; however, it is occasionally found on steep rocky slopes or along stream banks. It is tolerant of dry, infertile soils and can be quite invasive in rocky areas with a naturally open canopy. Most of the documented occurrences are in southeastern Pennsylvania and the Pittsburgh vicinity, however empress-tree probably occurs elsewhere in the state also; its northern spread is limited by the vulnerability of the flower buds to winter injury.”

So, current cultural practices are propelled by a market for the wood of this species, by historic associations with culture and heritage, by older reforestation practices, and, by traditional reforestation practices. Of course, science marches on, and whereas at one time states as diverse as Vermont, Kentucky, and Virginia may have recommended the planting of the princess tree, the overwhelming preponderance of evidence today affirms the danger to natural areas. Yet there is the short term market place which provides a demand which encourages industry to provide economically competitive sources of the wood. Also, the tendencies to reclaim severely challenged environmental sites with inexpensive solutions, sets the two sides of the discussion at logger-heads.

The historic nature of a planting ("The landscaping accentuates the central position of the Swann Fountain. Ever since Logan Circle opened in the 1920s, its princess trees (Paulownia tomentosa have been local favorites. Their clusters of purplish flowers appear in early spring, creating a mist of delicate colors. The surrounding beds of flowers and shrubs were originally designed in a formal French pattern, but have since been changed to a looser, more Romantic English style. Masses of tulips, dahlias, grape hyacinths, and azaleas bloom in season" seems to fall within a corner of invasive species issues which perhaps also includes arboretum and universities. As long as human collect things, there will be collections of exotica. Anyone currently suggesting that an arboretum grow only native would be faced with a public display of indignation. The issue perhaps is one of the good neighbor policy. Planting of known invasives should demonstrate a special need, perhaps such as historic accuracy. Care would be taken to assess the likelihood of escape and introduction to natural areas when deciding to plant. Management plans perhaps might be required.

In the end we return to the need for public education and involvement. Are we willing to pay more for long term benefits? Is it better to burn fossil fuels to bring the wood to North America, or should we grow it here to lower transportation costs?

1. Plant Conservation Alliance, Alien Plant Working Group
2. The Bugwood Network, USDA Forest Service and USDA APHIS PPQ.The University of Georgia - Warnell School of Forestry and Natural Resources andCollege of Agricultural and Environmental Sciences - Dept. of Entomo
4. Southeast Exotic Pest Plant Council Invasive Plant Manual
5. The Global Invasive Species Database

1. Plants For A Future
3. The American Paulownia Association, Inc.
4. Australian Paulownia Trees and Plantations
R. C. Kellison

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