San Diego Natural History Museum--Your Nature ConnectionSan Diego Natural History Museum Biodiversity Research Center of the Californias: Botany Department


Plant Atlas
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Field Guide

Natural History of Holiday Plants Exhibit
Evergreens | Holiday Color | Poinsettia | Holly | Mistletoe
Christmas Cactus | Christmas Tree | Common Holiday Plants


Ilex, photo courtesy of Norm Roberts Scientific name: Ilex opaca (New World) and Ilex aquifolium (Old World)
Plant family: Aquifoliaceae (Holly family)
Other common names: American Holly, English Holly, Christmas Holly

Holly is a plant frequently utilized to "deck our halls" during the holiday season. The boughs used to decorate typically are cuttings from any evergreen trees or shrubs in the genus Ilex. The most common holly species used are Ilex opaca from the eastern United States and Ilex aquifolium from Eurasia. Both species have spiny-margined, evergreen leaves, and usually exhibit red berries.

Are male or female holly plants most often used in holiday decorating?

If you are decorating with holly that has red berries, then you are using pistillate "female" plants. Many holly species are dioecious, which means that staminate "male" and pistillate "female" reproductive organs are separated on different individual plants. This sexual condition (dioecy) with individual plants bearing separate sexes promotes cross-fertilization, or outcrossing, which increases the genetic variability of the species but usually at the cost of lower seed-setting efficiency. Dioecy also prevents isolated individuals from reproducing on their own most of the time. Therefore, in most cases it is necessary that male and female plants grow in close proximity, or no red berries will be produced on the female plants for use during the holidays.

The Desert-Holly (Atriplex hymenelytra) that commonly grows in Anza-Borrego Desert State Park and in northeastern Baja California is not closely related to the holly (Ilex spp.) used during the holiday season. Although their common names suggest a close relationship, the name refers to its sharply-toothed leaves. Desert-Holly is a saltbush in the Chenopodiaceae (Goosefoot family) that is actually more closely related to beets (Beta vulgaris) and pickleweeds (Salicornia spp.) than to the evergreen decorative holly.

In the Cape region of Baja California Sur, there is a species of holly (Ilex californica) that can be found naturally occurring in the Sierra de la Laguna.

Continue to Mistletoe

Text by Jon P. Rebman, Ph.D., Curator of Botany;
Ilex sp., photo courtesy of Norm Roberts