Also known as "Helleri" or dwarf Japanese holly, Heller's Japanese holly (Ilex crenata "Helleri") is a dense evergreen shrub that generally thrives on neglect, tolerating urban conditions and requiring no pruning. If this tough shrub starts to turn brown, it may be suffering from pests, diseases or poor growing conditions. A good management strategy will improve cultural conditions to help the shrub become stronger and healthier.
Black Root Rot
Japanese holly is highly susceptible to black root rot, a fungus that attacks the root system and causes symptoms such as stunted growth, chlorosis and decline. Just under the soil surface, roots will be visibly black and rotted. Unfortunately, infected shrubs cannot be cured, according to the Clemson Cooperative Extension. Your only option is to remove the shrub. If you want to continue growing holly, choose a resistant species such as Chinese holly (Ilex cornuta), as black rot can remain active in the soil for years. Chinese holly may be grown in U.S. Department of Agriculture plant hardiness zones 7 to 9.
Hollies prefer a well draining, slightly acidic soil that is kept moist, but not water logged or flooded. In poor, alkaline soil, hollies may suffer from iron or manganese nutrient deficiencies that can cause the foliage to become yellow or brown. Compacted soil makes it more difficult for the plant to absorb nutrients. You may apply an iron or manganese foliar spray evenly over leaves to help the plant quickly absorb nutrients. Follow the label recommendations for dosage.
Heller's Japanese holly is very sensitive to drought, according to the Clemson Cooperative Extension, and requires regular watering. This is especially true when the shrub is newly planted. With inadequate irrigation, leaves may quickly turn yellow or brown. Winter damage may also cause leaves to brown or scorch on the edges. Monrovia recommends Heller's Japanese holly for USDA zones 6 to 9, while the University of Florida Extension recommends the shrub for USDA zones 5B to 8A. Plant Heller's Japanese holly in a bright, sunny location with shelter from drying winds.
If your holly has discolored brown patches, trails or holes in its leaves, you may have an infestation of foliage miners. Numerous larvae cause these symptoms. Luckily, an infestation of miners rarely becomes serious enough to kill a woody shrub. The University of California Statewide Integrated Pest Management Program recommends pruning out and disposing of infested foliage and avoiding broad-spectrum insecticides, which can kill beneficial predators. Water regularly to keep the shrub vigorous.
- Monrovia: Heller's Japanese Holly
- University of Connecticut Extension: Ilex Crenata
- University of Florida Extension: Ilex Crenata 'Helleri' Helleri Holly
- UC IPM: Mineral Deficiencies
- Clemson Cooperative Extension: Holly Diseases & Insect Pests
- UC IPM: Foliage Miners
- Missouri Botanical Garden: Ilex Cornuta