Caring for holly plants is generally easy as long as you understand the conditions in which they grow best. These handsome and varied plants range in height from upright trees of 60 feet to creeping plants 12 inches tall suitable for rock gardens. So there is a holly for almost every garden! Tolerating acid soil, hollies are good companion plants for rhododendrons. They’re known for their brightly colored, red fruit, but some varieties showcase orange, yellow, black or even white berries. The fruits sometimes lasts six months or longer, making hollies ideal ornamentals.
Holly Growing Conditions
Hollies prefer partial shade or full sun. They thrive in acidic soils with access to moist soil conditions. However, they do not tolerate poor drainage under cultivation. When growing in high pH soils, chlorosis can be an issue. Consistent soil temperatures (45°F to 48°F) are important for optimum growth and vigor. Hollies are most productive where annual precipitation is between 32 and 56 inches. They often grow near wetlands and springs to overcome regional drought. A holly’s root system is shallow and essential for holding soil along water resources. Holly roots assimilate nitrates and other associated nutrients that would otherwise run off into water supplies.
Hollies are air pollution tolerant. While American holly is more cold hardy than given credit, it is not wind tolerant in newly exposed locations. Therefore, you should not plant holly trees in extremely dry, windy, unprotected places. This is particularly true when the plant is young. Further, hollies do become more tolerant of their site as they mature. If protected from winter sun and desiccating winds, cold hardy selections should withstand -20 to -25°F.
One unique trait of holly is that there are dioecious, meaning there are separate male and female plants. Females produce berries, though the male plants do not. To ensure fruit, be sure to plant 1 male for every 2 to 3 females.
Pests and Diseases of Holly Plants
Using an Integrated Pest Management (IPM) approach is a best practice in caring for holly. It allows an arborist to identify insect and disease issues early and properly time the emergence of these pests to assure control.
Holly suffers from phytophthora, or a pathogen that lives in the soil, attacking roots first and then moving into the main stem, causing dieback. Black blotches form on the large and smaller stems. Waterlogged sites particularly stress these trees, making them more susceptible to the phytophthora pathogen as it moves through the roots.
Common insect pests include aphids, scale, and holly leaf miner. Regular monitor for these pests will help manage populations before damage can become widespread.
Cultural Tactics for Holly Care
- Provide soil analysis to create soil prescriptions.
- Transplant balled-and-burlapped or planted trees from a container in spring into moderately fertile, moist, loose, acidic, well-drained soil.
- Plant hollies using 1 male for every 2 to 3 females for pollination success and abundant berry production on the female trees.
- Administer micro-elements using a prescription for holly culture to create a pH range from 4.2 – 6.4 to assure optimum growth.
- Prune hollies in the winter for berry production and light prune obvious small deadwood.
- Destroy old leaves on the ground to prevent overwintering survival of holly leaf miner insects.
- Water during summer dry spells and just before winter months to super-charge around the hollies to prevent winter desiccation.
- Plant groupings of hollies in sheltered locations. Hollies protect each other from harsh winds and other environmental influences while creating protection and food stores for wildlife.
- Create ordinances in your community to protect holly trees during new home construction and general urban sprawl.