Phellodendron amurense

Leaves are dark green, compound and oppositely arranged with five to eleven leaflets. Photo credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

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Description

Amur corktree is a member of the Rue family (Rutaceae)
Amur corktree is a medium sized deciduous, dioecious tree growing up to 50 feet in height, given the right conditions. Its thick, corky bark is a good diagnostic feature, as are the conspicuous grape-like drupes (fruits), emerging towards the end of the summer. A member of the citrus family, its leaves are strongly pungent when crushed.

Leaves
Dark green, compound leaves are oppositely arranged with five to eleven leaflets. Leaflets are elliptical in shape, up to four and a half inches long, and smell strongly of turpentine when crushed. (5)

Flowers
Creamy yellow to white flowers in June are arranged in large, terminal clusters. (4)

Fruit/Seed
Amur corktree fruits are round, grape-like clusters of drupes up to half an inch wide which ripen to black in early fall. (1)

Introduction History

Amur corktree was introduced to North America from its native China in the 1850s. The extremely hardy, drought-, cold-, and pollution-tolerant species was commonly sold as a street tree, favored for planting in urban areas. The species is now present in at least 14 states. (3, 1)

Ecology and Habitat

Amur cork tree colonizes roadsides, old fields, woodland edges and other waste spaces. Although the species prefers moist, well-drained soil in full sun, it is a good competitor on depauperate, dry sites and can adapt to both alkaline and acid soils. (2)

Reproduction and Phenology

Female Amurcork trees are capable of producing thousands of seeds a year once mature. Each drupe contains five seeds which require no stratification prior to germination. Light and fire appear to increase germination rates of Amur corktree seedlings. Although no studies have been conducted expressly on the longevity of Amur corktree seeds in the seedbank, the species has a moderately hard endocarp, suggesting seeds may persist as viable propagules for at least several years. (1, 3). Vectors include birds and water. (9, 10)

Impacts of this species

Amur corktree is a shade tolerant, prolific seed producer capable of adapting to a variety of soil conditions. Due to its quick growing seedlings, young Amur corktrees can germinate and outcompete understory competition, rapidly converting diverse forests and woodlands to homogeneous stands. Furthermore, Amur corktree is known to be allelopathic, inhibiting the germination of seedlings of other plants and potentially modifying the species dynamics of native forest ecosystems in irreversible ways. (2) One study reports that Amur corktree gains an advantage over native vegetation in areas with high deer concentrations, as these herbivores do not eat this malodorous invasive. (12)

Management Methods

Biological Control
No biological control option is currently available.

Manual or Mechanical Control
Pulling / Digging Up: Hand pulling or digging young plants is effective, though time consuming. Larger plants can re-sprout from root fragments left in soil. (10)

Mowing: Mowing, weed whacking or cutting will cause larger individuals to re-sprout. This tactic is more effective when followed up with chemical treatment. (10)

Girdling: Girdling is an effective method of control if used with a chemical control method such as cut stump application Otherwise, re-sprouting will occur. (10)

Prescribed Fire: Controlled burns will eliminate seedlings and top kill larger trees. (11)

Prescribed Grazing: No information available

Soil Tilling: Not advisable as larger plants can re-sprout from root fragments

Mulching: No information available

Solarization: Not applicable

Hot Foam Spray: No information available

Chemical Control
Foliar Spray: A 3-4% solution of glyphosate, triclopyr, or Clopyralid is effective. Always read all instructions on the label. (10)

Cut Stump: A 50% solution of glyphosate applied immediately to cut stems is effective in controlling this species. (11)

Basal Bark: A 25% solution of triclopyr is effective when applied from early fall through winter. (11)

Stem Injection: No information available

Pre-Emergent Spray: No information available

Frill and Spray: Apply a 50% solution of glyphosate or triclopyr to cuts in Amur cork tree’s cambium. (13)

The pesticide application rates and usage herein are recommendations based on research and interviews with land managers. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be listed on a pesticide label, requiring a 2(ee) exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator.

Summary of Best Managment Practices

General management overview and recommendation
As with any other invasive infestation complex, large stands of Amur cork tree are best managed via a combination of mechanical and chemical means. Larger individuals should be treated with a cut stump or basal bark or frill and spray herbicide application, while small individuals can be pulled or sprayed. All managed infestations should be monitored for several years to ensure exhaustion of the seed bank and to monitor for any re-sprouting. Any new seedlings can be hand pulled. New sprouts must be treated with foliar spray or continued re-cut of the new growth.

Post treatment monitoring
Controlled populations should be revisited at least 2 times a season for at least 4 years to ensure exhaustion of the seed bank and to check that no re-sprouting has occurred.

Disposal Methods
Mowed, cut, or pulled Amur cork tree can be composted or chipped so long as management occurred prior to fruiting.

Additional Information

REFERENCES

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