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The Ilex opaca is a species of evergreen tree, also known as the American holly. Native to the southeastern part of the United States, the tree reaches a maximum mature height of up to 50 feet (about 15 meters) in its native environment, though landscape trees are generally much smaller. Its green leaves and bright red berries are often used in Christmas decorations, including wreaths and garland.
Also known as dune holly, Christmas holly and scrub holly, the Ilex opaca can be found growing wild in the US states south of Delaware. Generally the farther south the trees are found, the larger they get. The trees have a relative slow growth rate and are very tolerant to shady areas; they are often found growing among and beneath larger trees, such as pines.
The tree has leathery leaves similar to those of other types of holly. The leaves are evergreen, dull in color, about 3.5 inches (8.8 cm) long, and are supported by a maze of crooked branches. Flowers appear in the late spring, typically in June, and are small and white. Male and female trees are easy to tell apart during the time they flower, as female flowers bloom one to a stalk and male flowers bloom in clusters. Since the trees are either male or female, more than one must be planted in the area for fertilization; the formation of the holly's distinctive berries only occurs if there has been pollination.
After the flowers bloom, the female pollinated Ilex opaca form small red berries that are actually the seeds. These berries and the evergreen leaves are a popular image for Christmas, and berries remain on the trees even in areas with cold, snowy winters. They are generally not appetizing to deer or other animals, and can make attractive accent trees that bring color to what would be an otherwise white landscape.
These slow-growing trees have a long life span, and specimens have been found that are more than 100 years old. There have been some instances in which areas have been wiped almost barren of holly trees because of the desirability of their branches for winter decoration. Laws have been passed in some US states to protect the wild trees, and this has allowed the Ilex opaca to flourish.
The Ilex opaca has been hybridized to form a number of cultivars. Some have leaves that are a darker green than the parent plant, and others sport yellow berries instead of red. Since these berries are such a desirable feature of the tree, some cultivars have been created to bear more berries than the parent original. Most of the trees selected as landscape plants are one of the hybridized cultivars.