Descriptions and photos of five nonnative (alien) invasive tree species of Virginia. Focus on history, importance in built landscapes and, control and management.

Overview

In September 2003, The Virginia Department of Conservation and Recreation, Division of Natural Heritage and the Virginia Native Plant Society listed as invasive five alien (nonnative) tree species:

1. Ailanthus altissima (Tree-of-heaven),
2. Albizia julibrissin (Mimosa or Silktree),
3. Melia azedarach (Chinaberry, Pride-of-India, Persian Lilac or Bead-tree),
4. Paulownia tomentosa (Princess Tree, Royal Paulownia or Empress Tree),
5. Morus alba (White or Common Mulberry).

Government Action

In 2006, Governor Tim Kaine established a thirteen member Invasive Species Working Group and a nineteen member Invasive Species Advisory Committee. These groups are responsible for efforts to:

• Prevent invasive species from entering Virginia, and
• Manage problem species already established in the Commonwealth.

They will also:

• Implement a state invasive species management plan,
• Develop a list of high priority invasive species, and
• Maintain a website.

Hold on Built Landscapes

All five plants make interesting and attractive landscape trees despite rampant spreading and reproductive characteristics. Though out of control and a threat to natural environments, they are easily available and attractive to landscape gardeners.

An example is Ailanthus altissima (Princess Tree) in an avenue planting near the entrance of Longwood Gardens (Kennett Square, PA). Their two-inch-long pale violet flowers are impressive seen across the "Cow Lot" in Longwood's Central Outdoor Gardens.

Tree Descriptions

Highly Invasive

Ailanthus altissima (Tree-of-heaven), Chinese native, is fast growing and produces copious seeds and persistent stumps and root sprouts. It survives where few trees do and competes aggressively with surrounding vegetation (phytotoxic). A Tree Grows in Brooklyn (1943) by Betty Smith shows the toughness of this tree.

The Tree-of-heaven came into the U.S. via two routes:

• William Hamilton, a Philadelphia plantsman, brought saplings from England around 1784. By 1840, the Tree-of-heaven regularly sold in eastern nurseries because of its fast growth and beautiful foliage.
• Chinese migrants, during California gold rush days, brought Ailanthus seeds with them.

Moderately Invasive

Albizia julibrissin (Mimosa or Silktree), Iran to China, is a small ornamental that exhibits pale pink powder-puff-like flowers throughout summer months. It adapts easily to a wide variety of soil conditions and high winds. It spreads by suckers growing from roots.

André Michaux, a French citizen, shared mimosa seeds upon arrival to the U.S. in 1758 with Philadelphia plantsman William Bartram. Ultimately, William Hamilton and Thomas Jefferson planted mimosas.

Melia azedarach (Chinaberry, Pride-of-India, Persian Lilac or Bead-tree), northern India, is famous worldwide for its fragrant lilac flowers and shade-producing qualities. Michael A. Dirr labels Melia as a weed tree, adaptable to most situations. Melia produces abundant animal-dispersed fruit and sprouts vigorously from stumps and deceptively-looking dead trunks.

André Michaux listed Chinaberry in North American Sylva (1819) because it was already well established in the southern U.S. . Chinaberry is currently listed as one of sixteen most prevalent exotic trees in southern U.S. forests.

Paulownia tomentosa (Princess Tree, Royal Paulownia or Empress Tree), China, came to the U.S. about 1840 as an ornamental cherished for spring flowers, stately appearance and fast growth. It adapts to a wide variety of soils, and withstands air pollution.

Each abundant, nondescript Paulownia fruit capsule contains upwards of 2000 viable seeds. Stressed trees sprout from roots and these can grow more than 15 feet in a single season.

Western botanists named this tree for Queen Anna Pavlona of The Netherlands (1795 - 1865), daughter of Tsar Paul I of Russia. Anna Paulowna is 19th century Dutch for Anna Pavlovna.

Occasionally Invasive

Morus alba (White or Common Mulberry), China, traveled to North America with Jamestown, VA settlers,about 1608. Mulberry leaves serve as food for silkworms, while other plant parts supply textile- and paper-making, pesticides, furniture, musical instruments, sculptures, and medicines.

The white mulberry is exceptionally tolerant of hostile growing conditions and produces fruit preferred and spread by birds. It may develop witches' brooms that make it look unkempt. Dirr refers to the white mulberry as a garbage can tree.

© Text by Georgene A. Bramlage. 2008. Reproduction without permission prohibited.