Holly, or Ilex, is an evergreen tree that ranges in size from 6-inch-tall dwarf varieties to large, 70-foot specimens. These trees offer year-round green foliage and colorful berries that may attract birds. Holly trees are diverse. There are over 400 species which can be used as climbers, shrubs and landscaping trees.
Holly trees prefer well-drained soil, rich in organic matter. These acid loving trees will grow in partial shade but need full sun for berry production. In addition, most hollies need both a male and female plant in order to properly pollinate and produce berries on the female plant. Some varieties of holly are self-pollinating. Only female plants and self-pollinating plants produce berries. Ask at your local nursery if the holly you have selected is self-pollinating, male or female.
Hollies can be used for a variety of landscaping purposes. Commonly they are planted for their berries, which provide a backsplash of color throughout the bleak winter landscape. However, these trees are also used as privacy screens, foundation plantings and low hedges.
According to Clemson University Extension, holly trees are susceptible to a number of diseases including black root rot, Phytophthora root rot, tar spots and nematodes. Both forms of root rot will cause damage to the plant's root system and will decrease growth. Black root rot is caused by a fungus, Thielaviopsis basicola, found in the soil. Phytophthora root rot, however, is caused by wet soil conditions. Tar spots, caused by a fungus, are small, yellow spots on the holly leaves. These spots eventually turn black and fall out of the leaf. Nematodes are parasites that feed by sucking juices from plant cells. Although there are currently no control methods against nematodes, a fungicide such as thiophanate-methyl will address holly related diseases.
Insects associated with holly trees include southern red mites, leafminers and scales. Horticultural sprays are effective against both mites and scales. Leafminers can be treated by handpicking and destroying infested leaves.
Holly berries are poisonous to humans and pets. These trees should not be used if the berries may threaten small children or household pets. In areas where deer infestation is abundant holly trees may act as a deterrent. Deer and other wildlife, such as rabbits, rarely eat hollies due to their sharp leaves and berries.