Spread a 2 to 4 inch layer of some attractive organic material like chopped leaves, pine needles, or wood chips on the soil under each Holly tree.
Holly normally does not need supplemental watering except when it's first planted, in time of drought, or in late fall before the ground freezes for the winter. Even well established trees will need watering during severe drought.
Pruning Hedges – Japanese Hollies and others that are pruned into hedges can be pruned in late spring or early summer after the new growth has hardened off. When shaping hedges, do not cut lower branches shorter than higher ones. Hollies that are narrower at the bottom than the top often lose these lower branches, and sometimes the whole shrub actually dies.
Tip – After pruning hollies with leaves with spines, be sure to pick up all the leaves and dispose of them. If stepped on by a bare foot child, they can be painful.
Fertilizing - Hollies are sensitive to over fertilization. They need only one application each year of a slow-release granular fertilizer designed for acid-loving plants. In the fall sprinkle this fertilizer on the soil under the tree out to 1-1/2 feet beyond the branch tips (drip line). About 1/2 pound of fertilizer is sufficient for Hollies with a trunk diameter of 1/2 inch at the base. For larger ones, use 1 to 2 pounds for each inch of trunk diameter.
Winter Protection - Severe winter conditions, and sometimes soil deficiencies, may cause physiological problems such as sunscald and purple spot on the leaves of evergreen Hollies. Winds blowing the spiny leaves together cause punctures in Holly foliage. Spray Holly leaves with anti-transpirant spray to protect their surfaces from harsh winter sun and wind. Consider erecting a wind barrier of burlap or similar material around Holly trees and shrubs that are exposed to prevailing winter winds. Never wrap a tree or shrub with plastic. Spread winter mulch on the soil over the roots after the ground freezes.
Pruning - Chinese Hollies do not require regular pruning, because of their naturally compact pyramidal or mounded shape. American Hollies require routine pruning. Regularly pyramidal as young trees, they tend to become more open and irregular as they age and some homeowners prune them to maintain a tighter shape. Prune to shape Hollies into hedges or to remove dead or diseased growth, or trim the bottom branches off trees to expose the trunk.
Prune Holly when plants are dormant in the winter. Christmas is an excellent time. American Holly can be lightly pruned almost any time of the year, but keep in mind that if the plants are pruned heavily after flowering, or during the summer months, berry production may be reduced. Never "top" a Holly tree by cutting off its central stem to reduce its height.