By Julie Christensen
American holly trees (Ilex opaca) were valued long before Europeans arrived. Native Americans dried the berries and used them for buttons or decorations. They also used the hard wood for various purposes. In the landscape, American holly trees make excellent specimen trees, hedges or street trees. Although they can grow to 60 feet tall, they usually remain under 20 or 30 feet. These evergreen trees have an attractive pyramidal form. The leaves are glossy and bright green, with a traditional holly shape and barbed edges. Small, white flowers in spring are followed by clusters of bright-red fruit in the fall. The fruit remains on the trees through the winter and is attractive to wildlife and birds, although it is toxic to humans. American holly trees are dioecious, so be sure to plant a male tree as well as a female to ensure fruit production.
Planting American Holly Tree
Plant American holly trees in spring through summer from potted nursery plants. This tree is hardy in USDA plant hardiness zones 5 through 9. Select a location for American holly with partial to full sun. Although wild holly trees often grow as understory trees in partial shade, the female trees will produce better fruit if they’re planted in full sun.
Plant American holly in moist, well-draining soil with a pH below 6.5. Before planting American holly trees, dig compost or peat moss into the soil to improve drainage. Amend alkaline soils with sulfur and use acidifying fertilizers. Dig a hole as deep as the root ball, and at least twice as wide. Remove the plant from its pot and set it gently in the hole. Fill the hole half full of soil and add two gallons of water. Let the water drain and add the remaining soil, tamping it down firmly.
Water a newly planted tree at least weekly, or as often as needed to keep the soil consistently moist, but not soggy. Once established, American holly trees can tolerate mild drought. In consistently dry conditions, they’ll produce few fruit and the foliage may become thin.
American holly trees grow quite slowly. It’s not uncommon for a tree to grow only 20 to 30 feet in 40 years. The trees may not need any fertilizer, especially if they’re planted in a fertilized lawn, but you can apply an acidifying fertilizer in spring, according to package directions.
Pests and Problems
The most common insect pests that afflict American holly include scale insects and spider mites. Both these insects cause wilting, or speckled or stippled leaves. Treat small trees with insecticidal soap or oil. Larger trees are difficult to treat, but the damage is usually mild.
American holly trees suffer from several fungal and bacterial leaf spots and cankers. In most cases, these diseases aren’t serious. To prevent diseases, keep the tree healthy through adequate watering. Rake up leaf litter and discard promptly. Make sure American holly is planted in moist, but well draining soils to reduce the risk of root rots.
On alkaline soils, American holly trees develop iron chlorosis, which occurs when the trees can’t access iron from the soil. The main symptom is yellow leaves with green veins. To prevent this problem, avoid planting American holly trees on soils with a pH above 6.5. You can also lower the soil pH with sulfur and acidifying fertilizers.
Harsh winter weather can cause the plants to become scorched and browned. If you live in the north, plant American holly trees in an area protected from fierce winds and bright winter sunlight.
American Holly Varieties
- ‘Howard’ is a compact cultivar with glossy green leaves with few barbs and large berries.
- ‘Greenleaf’ responds well to pruning, making it the best choice for a hedge form.
- ‘Canary’ and ‘Morgan Gold’ have yellow fruit, rather than the more common red.
For more information on growing American holly trees, visit the following links:
American Holly from North Carolina State University Extension
American Holly from the Fairfax County Public Schools
American Holly on YouTube.
Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.