Nellie Stevens Holly Trees can be easily manipulated into the desired shape. They are usually planted to form a living privacy wall but can also be allowed to grow in a natural pyramidal form. At maturity, the tree is between 15 and 25 feet tall. Without pruning, healthy Nellie Stevens trees can grow as much as 3 feet annually. Disease is not common, but as with any tree, the holly can be prone to attacks from insects such as aphids which produce a substance that leads to a black surface growth called sooty mold.
Prune wilting, damaged and dying leaves. Cut them off where they meet healthy wood. Make clean, non-ragged cuts.
Remove black soil that may be growing at the base of the Nellie Stevens Holly tree. Put it and the dying leaves in a plastic bag for disposal. Do not leave it on the ground or in a compost pile because the disease can spread.
Thin out the branches and foliage growing at the bottom of Nellie Stevens. This will allow air to circulate more freely. Sunlight will also be better able to reach the bark and soil.
Keep weeds at bay. They will encourage pest and insect infestations. Pull or rake them away from the holly tree.
Use a registered insecticide at the first sign of mealybugs, aphids or whiteflies. Follow the instructions on the label pertaining to application and precautions. There are also organic products on the market.
Check drainage around the Nellie Stevens Holly Tree. If the water is pooling, this can cause the tree to die. You may need to add sand to the soil or dig a trench to enhance drainage .