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Description

The common name Trifoliate Orange is in reference to the three-lobed leaves and orange fruit. This shrub grows 8-15 feet tall. The white flowers have 4-7 petals and are fragrant and showy, and the stems are covered heavily with sharp thorns. The leaves emerge as a yellowish green and turn dark green by summer, and fall off the tree in autumn. The fruit are edible but they are very acidic, sour, and seedy. They ripen to a bright yellow and are usually 1-2.5 inches in diameter.

Ecological Threat

This hardy and thorn-laden shrub is able to invade woodlands, forest edges, and disturbed urban areas such as fence rows and green spaces. They grow in the understory very rapidly, and are able to shade out native plants. Their vicious thorns do not provide adequate habitat or shelter for nesting birds, squirrels or burrowing animals.

Biology

Flowers bloom from April to May, fully covering the branches. Fuzzy green fruit appear from July to October and contain multiple seeds within They ripen to a bright yellow. Animals help disperse the seeds.

History

In the 1850s it was introduced from China and Korea, possibly as a thorny hedge to confine livestock. It has fully established throughout Louisiana, prominent in Arkansas, and is now present in over 15 counties in Texas.

Native Origin

Central and northern China

Current Location

U.S. Habitat: Ideal in full sun exposure in soils with medium moisture. It is not cold tolerant.

U.S. Present: AL, AR, DE, FL, GA, LA, MD, MO, MS, NC, OK, PA, SC, TN, TX, VA and WV.

For a state and county distribution map provided by the PLANTS database click here.

Resembles

Initially placed in the Citrus genus, its fruit closely resembles those Citrus species. The thorns and fruit can also resemble the Osage-Orange, Maclura pomifera.

Management

With the plant being covered in thorns, mechanical management can prove to be quite difficult. However, it does respond well to bulldozing when the fruits are not present. If you find new plants, pull them or treat them chemically before fruits can be formed. The hardy orange does respond to chemical treatments with glyphosate, triclopyr or a combination of the two. The herbicides work better after the plant has been freshly cut and the chemicals are directly applied to it.

References

Dansereau, K. 2007. The Role of Plant Water Deficits on Cold Tolerance during Cold Acclimation of a Cold Tolerant (Poncirus trifoliata) and Cold Sensitive (Citrus unshiu) Species. (Doctoral dissertation).

Nesom, G. Citrus trifoliata (Rutaceae): review of biology and distribution in the USA.

Webber, H. J., & Swingle, W. T. 1906. New citrus creations of the Department of Agriculture. Scientific American, 62, 25784-25787.

Yelenosky, G., Brown, R. T., & Hearn, C. J. 1973. Tolerance of trifoliate orange selections and hybrids to freezes and flooding. In Proc. Fla. State Hort. Soc (Vol. 86, pp. 99-104).

Internet Sources

http://plants.usda.gov/core/profile?symbol=POTR4

http://www.invasiveplantatlas.org/subject.html?sub=11571

http://www.uaex.edu/yard-garden/resource-library/plant-week/hardy-orange-2-9-07.aspx

http://www.invasive.org/publications/ipsf/TrifoliateOrange.pdf

http://wiki.bugwood.org/Archive:MGIPSF/Trifoliate,_Hardy_Orange