American Holly Ilex opaca 'Clarendon Spreading'

'Clarendon Spreading' is an all-female cultivar of the American holly in the Aquifoliaceae (holly) family.  The genus name Ilex is in reference to the similarity of the evergreen leaves to Quercus ilex or holm oak.  The specific epithet opaca means dull, dark or opaque in reference to the dullness of the leaf surface.

This broadleaf evergreen shrub grows 3 to 4 feet tall and 8 feet wide.  Plants have been known to live to 80 years.  It has alternate leaves with spiny toothed and sometimes smooth margins. The bark is gray-white in color and may be splotched or warty. Small, dull green-white, solitary flowers mature in late spring. Female specimens produce a bright red or orange fruit which matures in the fall and persists into the winter. Being dioecious, plant one male for every 6 female.  

The American holly is easily grown in average, consistently moist, acidic, well-drained soils in full sun to part shade. It will tolerate a broad range of soil conditions and is pollution tolerant, but will not tolerate flooding or soils saturated with moisture. For optimum growth avoid poorly drained soils. Its best growth in the wild usually occurs in rich bottomlands and swamp margins. It will not do well in locations not protected from cold winter winds and winter sun. Part afternoon shade is best in hot summer climates. Being situated in too much shade will cause the plant foliage to lose density.

Uses this low-growing shrub as a specimen or plant in small groups along a foundation or slope.  It makes an excellent small hedge and its dark green leaves and red fruits provide interest in a winter landscape. Branches from this species are often used in the creation of Christmas wreaths.  

It is a food source for Henrys elfin (Callophrys henrici) caterpillar.

Fire Risk: This plant has a high flammability rating and should not be planted within the defensible space of your home. Select plants with a low flammability rating for the sites nearest your home. 

Quick ID Hints:

• Dull, dark green leaves are both entire and spiny.
• Spines are evenly spaced and are long and sharp.
• Leaves usually have a dull, dirty look.

Insects, Diseases, and Other Plant Problems:  Insects that can potentially cause issues are holly leaf miner, spider mites, scale and whitefly.  Diseases can include powdery mildew, leaf rot, leaf spot, and tar spot.   Planting in soils that have a high pH can cause leaf drop, leaf scorch, and chlorosis.  

The Clemson Cooperative Extension Home and Garden Information Center has a factsheet on common diseases and insect pests.

VIDEO: Part of a series of Native Plant Picks from the North Carolina Sea Grant Coastal Landscapes Initiative.

Additional Ilex opaca video created by Andy Pulte for “Landscape Plant Identification, Taxonomy and Morphology” a plant identification course offered by the Department of Plant Sciences, University of Tennessee.