Holly trees provide the garden with visual interest with their characteristic evergreen foliage and bold red berries. Choose the holly tree that grows best in your region and provide consistent care. Dahoon hollies (Ilex cassine) reach up to 40 feet in height and thrive in U.S. Department of Agriculture plant hardiness zones 7a through 11. American hollies (Ilex opaca) grow up to 50 feet tall and perform best in USDA hardiness zones 5b through 9. Yaupon hollies, however, grow to only 20 feet tall and thrive in USDA hardiness zones 7 through 9.
Cut back with pruning shears any plants that create excessive shade near holly trees, as these plants thrive in full sun to partial shade.
Maintain moist, well-drained soil unless growing a dahoon holly, which thrives in wet conditions. Improve soil drainage and increase fertility by incorporating organic content, such as compost, into the uppermost layers of soil. Irrigate soil when the top layer feels dry to the touch; though these trees tolerate drought, they thrive in consistent moisture.
Lay a 2- to 3-inch layer of organic mulch, such as wood chips, on the soil surrounding the holly tree without pressing the mulch against the trunk. Mulch decreases soil pH, keeps weeds at bay and conserves moisture.
Test your soil by taking a soil sample to a lab; contact a local extension office for a lab referral. Make necessary amendments to the soil, such as changes to improve the nutrient balance. Holly trees are susceptible to poor fruiting as a result of high nitrogen levels.
Examine holly trees for sucking pests, such as scales or red mites. Identify scales by their small, immobile bodies that look like bumps on foliage and twigs. Search for scale damage, including yellowed, distorted leaves. Identify southern red mites by their damage, as they are nearly invisible to the naked eye. Look for leaves that become bronzed before falling to the ground. Release natural enemies onto the tree, such as parasitic wasps for scale control, or predatory mites for mite control, as a form of biological management. Apply horticultural oil to the entire plant to kill pests on contact.
Examine plants regularly for common disease problems, such as root rot diseases caused by fungal pathogens. Look for yellowing leaves that drop early, wilting, diminished health and limb dieback. Apply fungicides for control. For example, apply a fungicide with an active ingredient, such as etridiazole, to trees suffering from Phytophthora root rot. Remove and destroy severely affected holly trees. Replace the tree with a more resistant species, such as Chinese holly (Ilex cornuta), which thrives in USDA hardiness zones 7 through 9.
Things You Will Need
- Pruning shears
- Organic mulch
- Parasitic wasps
- Predatory mites
- Horticultural oil
- Gardening gloves
- Protective eyewear
- Avoid waterlogged soil, which encourages root rot and fungal disease.
- Always wear gardening gloves and protective eyewear to prevent injury when handling dangerous tools, such as pruning shears and/or fungicides.
- University of Florida IFAS Extension: Ilex Cassine -- Dahoon Holly
- University of Florida IFAS Extension: Ilex Opaca -- American Holly
- North Carolina State University Cooperative Extension: Ilex Vomitoria
- University of Florida IFAS Extension: Hollies for the Holidays
- Clemson Cooperative Extension: Holly
- Clemson Cooperative Extension: Holly Diseases & Insect Pests
- North Carolina State University Cooperative Extension: Ilex Cornuta
- Jupiterimages/Photos.com/Getty Images