Holly trees provide the backyard with visual interest using their feature evergreen foliage and bold red berries. Select the holly tree which grows best on your area and provide consistent care. Dahoon hollies (Ilex cassine) reach up to 40 feet in height and also prosper in U.S. Department of Agriculture plant hardiness zones 7a through 11. American hollies (Ilex opaca) develop 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 prosper in USDA hardiness zones 7 through 9.
Cut back with pruning shears any plants which create excessive shade near holly trees, as these plants thrive in full sun to partial shade.
Preserve moist, well-drained dirt unless expanding a dahoon holly, which thrives in wet conditions. Increase soil drainage and increase fertility by integrating organic content, like compost, in the uppermost layers of dirt. Irrigate dirt once the upper layer feels dry to the touch; though these trees bear drought, they prosper in constant moisture.
Put a 2- to 3-inch layer of organic mulch, such as wood chips, on the ground surrounding the holly tree without pressing the mulch from the trunk. Mulch decreases soil pH, keeps weeds at bay and also conserves moisture.
Test your soil by taking a soil sample to a laboratory; contact a local extension office to get a laboratory referral. Make necessary amendments to the ground, like changes to improve the nutrient balance. Holly trees are vulnerable to poor fruiting as a consequence of high sulfur levels.
Examine holly trees to get sucking pests, like red or scales mites. Identify scales by their small, immobile bodies which look like bumps on leaf and twigs. Search for scale damage, such as yellowed, distorted leaves. Identify southern red mites by their damage, as they are nearly invisible to the naked eye. Look for leaves which eventually become bronzed before falling to the bottom. Release natural enemies onto the tree, like parasitic wasps for scale control, or predatory mites for mite management, as a form of biological management. Apply horticultural oil to the whole plant to kill pests on contact.
Examine plants regularly for frequent disease complications, like root rot diseases brought on by fungal pathogens. Look for yellowing leaves which fall early, wilting, diminished health and limb dieback. Apply fungicides for control. For example, apply a fungicide having an active ingredient, like etridiazole, to trees suffering from Phytophthora root rot. Remove and destroy severely affected holly trees. Replace the shrub with a more resistant species, like Chinese holly (Ilex cornuta), that thrives in USDA hardiness zones 7 through 9.