Native Plant of the Week - American Holly

This week's Native Plant of the Week is Ilex opaca, American Holly. American holly is an evergreen tree native to the mid-Atlantic region. “Ilex” is the botanical name for all plants in the holly genus. “Opaca” is from latin “opacus” (opaque) presumably because of its dark, lustrous leaves. These plants are dioecious, which means that a plant is either male or female. A male plant (androecious) has flowers that produce pollen only, but no seed. A female plant (gynoecious) produces seeds, but no pollen.  It is the females that bare the red berries. Generally, we need 1 male nearby for every 10 females in order for cross pollination to occur. Without, the females would not bear fruit. Bees and wasps are the primary pollinators for the American holly.

The berries of the American holly are an important food source for many birds including wild turkeys, 3 types of woodpeckers, cedar waxwings, bluebirds and robins. I have seen 40’ tall trees shaking vigously as dozens of Robins devour the berries and virtually denude the tree in mid-January! The new growth is one of the primary larval food sources of the Henrys Elfin butterfly.

In May, the hollies flush out new growth. At this time, the leaves that were produced 2 years earlier are dropped.  This leaf drop is perfectly normal, but can be alarming to those who are unfamiliar with the growth habits.

American hollies prefer partial shade and well drained soil. A drive around the beltway in the winter will reveal more hollies growing naturally in the lightly wooded areas on the eastern side (PG County) than in the western side (Montgomery County). Presumably the sandy soil on the eastern side of DC drains better than the heavier clay soil found on the western side.

If the goal is to display the berries, a light summer trimming will help. The fruit is set where the flowers were borne in June. Then, 6 to 8 inches of growth flushes out beyond the flowers. This growth partially masks the fruit. Growth generally stops in August. This can be done for most hollies where the berry display is important.

Other than it’s ornamental value, the American Holly has very little commercial value except for it’s very white colored wood which is prized for veneer inlays.