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DNR invasive species staff
Amur cork tree

Amur cork tree
(Phellodendron amurense)

Distinct tree with thick corky or spongy outer bark, and bright yellow inner bark. Leaves are opposite pinnately compound and faintly smell of citrus when crushed. Trees have strong, rot-resistant wood.

Overview

Regulated areas of Amur cork tree
This species is Prohibited (Red counties)

Other names for this plant include:

  • Common names: Amur cork tree
  • Scientific names: Phellodendron amurense

Ecological threat:

  • Suppresses regeneration of native tree species and displaces native shrub and herbaceous layers.
  • Research shows decreases in acorn and hickory nut production as well as overall tree populations where Amur cork tree is present.
  • Adaptable to different soil types (clays to sands), acidic to alkaline, but preferring moist, well-drained soils.
  • Grows in both full sun and under dense shade.
  • Reproduces by both seed and by resprouting from stumps. A female tree can produce 1000's of seeds.
  • Allelopathic; chemical exudates alters soil microorganisms and surrounding vegetation.
  • Grown throughout the United States; tolerant of urban areas (pollution, parking lots, golf courses, highway medians).

Classification in Wisconsin: Prohibited *Exempt male cultivars and seedling understock.

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for Amur cork tree was based upon this literature review developed by the department.

Identification

Leaves & stems: Distinct thick corky or spongy outer bark; cutting into the bark reveals bright yellow inner bark. Opposite pinnately compound leaves smell somewhat of citrus or disinfectant when crushed. Leaflets are entire and dark green, turning yellow in fall. Can resprout from cut-stumps.

Flowers: Both male and female flowers (on separate trees) are greenish panicles.

Fruits & seeds: Trees are dioecious, producing fruit only on female plants. Fruits are drupes (fleshy fruit with a single stone), green in color, turning black in fall. Fruits remain on trees into winter.

 

Distribution

Phellodendron_amurense
Counties in WI where Amur cork tree has been reported (as of April 2013). Both vouchered and unvouchered reports included.

Do you have Amur cork tree in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical:

  • Control should prioritize removal of female (fruiting) trees first.
  • Trees can be controlled by girdling.
  • Resprouts vigorously if not treated after cutting.
  • Follow up with replanting of desirable species.

Chemical:

  • Treatment can include hack and squirt (frilling), cut stump treatments, or basal bark treatments.
  • Systemic herbicides include triclopyr and glyphosate.
  • Treat with a foliar spray of Transline (1 oz/gal) in mid-summer, pre-bloom to bloom stage.
  • All trees larger than 3" can be cut and treated with either Tordon or Element 4. Smaller trees can be treated with foliar applications of Element 4 (3-4%).
  • A cut-stump treatment applied with Crossbow (2, 4-D + triclopyr) with diesel.

Photos

View Amur cork tree pictures in our photo gallery!

Resources

Sources for content:

  • Elizabeth J. Czarapata. Invasive Plants of the Upper Midwest: An Illustrated Guide to Their Identification and Control. Madison, WI: University of Wisconsin Press, 2005.
  • Plant Conservation Alliance's Alien Plant Working Group
  • Center for Invasive Species and Ecosystem Health; Invasive.org

Links for More Information

Last revised: Tuesday April 28 2015