Aucuba (spotted laurel) is recommended for its robustness and ability to grow in dry, shaded sites. However, despite this reputation, Aucuba can become stressed such as when its roots become waterlogged during cold, wet winters, for example, and as a result the leaves and shoot tips turn black.
The leaves (and shoot tips) develop moist blackened areas. There is no evidence that a pest or disease causes this and there is no need to apply pesticides.
The blackening of the leaves is usually caused by root stress due to excess moisture levels in the soil during cold, wet winters. Other forms of stress, including root diseases (mainly phytophthora root rots) might also be involved.
There are no chemicals to control (or prevent) Aucuba blackening. If it happens in your garden do the following:
- On established plants remove any affected foliage and shoots
- Encourage strong regrowth by applying a balanced general fertiliser around the base of the plant in early spring
To prevent Aucuba blackening, try the following:
- Avoid planting Aucuba in areas prone to waterlogging
- Improve texture and drainage of heavy clay soils prior to planting by incorporating bulky organic matter such as composted bark, garden compost or well rotted farmyard manure to a larger area
- In wet districts planting on low, wide mounds, about 20cm (8in) high can help
- Mulching with bulky organic matter can be also beneficial. Keep the base of the plant free from mulch