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August 2010

No Comparison Between Apples and ...
Trifoliate Orange

Contact: Marc Imlay, Mid-Atlantic Exotic Pest Plant Council, Maryland Native Plant Society | ialm@erols.com

trifoliate orange
Photo: Nancy Fraley, USDI National Park Service, Bugwood.org
trifoliate orange
Photo: John D. Byrd, Mississippi State University, Bugwood.org

ANNAPOLIS, MD (August 9, 2010) - Trifoliate orange, Poncirus trifoliata is commonly known as hardy orange and has been found to be highly invasive in southern states. For example, it invaded floodplains along Robeson Creek in Chatham County, North Carolina, where it forms dense thickets. So far a preliminary investigation reveals that trifoliate orange only shows up in scattered locations in Maryland, D.C. and Virginia but is not yet a very serious invasive in Maryland. The National Park Service did not find it on areas in Maryland that they manage, however it was found by others in Swann Park in Charles County, and by Trumbule Trail in Magruder Woods in Hyattsville, Prince Georges County. Due to its invasive qualities and its strengthening foothold in Maryland, the Maryland Invasive Species Council has chosen trifoliate orange to be the August Invader of the Month.

Trifoliate orange is a deciduous shrub or small tree that grows from 8-30 feet in height. The leaves are alternate, compound with three leaflets (trifoliate), up to 2 inches long and have a winged petiole or stem. The twigs are green with stout sharp 1 inch long thorns. The bark is conspicuously green-striped. Spring flowers are white with 5 petals, 1-2 inches in diameter and showy. The fruit looks like a small orange it is golf ball sized, dull yellow, and sticky to the touch. The fruit is very bitter but is sometimes used for marmalade.

As is the case with many invasive species, trifoliate orange was introduced intentionally for the purpose of beautifying the landscape. Due to its hardy nature it is often used as rootstock for citrus trees. Originally from China, trifoliate orange is popular with homeowners for its unique form and green color. Trifoliate orange needs to be watched closely since it can easily become established and create even more competition for desirable trees in forest settings. Because of the spiny stems deer will most likely avoid browsing on it which gives it a leg up when compared to most native plant species.

To prevent the spread of trifoliate orange, do not plant it; choose alternative plants, and eradicate the plants you find outside of a landscaped setting. Alternatives for trifoliate orange include: winterberry holly, which has colorful red berries that attract birds throughout the winter, and American holly, which is another evergreen with spiny leaves that can be planted for privacy, security or beautification. Control can be achieved by hand pulling seedlings or for larger specimens the cut stump application of an herbicide. Contact your local state forestry office or University of MD Cooperative Extension office for specific recommendation and as always follow label directions. To be safe use basic precautions like gardening gloves, long pants/long sleeved shirts, and eye protection.

For more information, please visit:

SC-EPPC Invasive Plant List

For more information about Invasive Species of Concern in Maryland, visit www.mdinvasivesp.org

photos available electronically on request.

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