These are causes for browning across part of the leaf, and the controls.
Brown leaf tips or margins
Brown tips or margins often indicate drought in spring or summer. Young growth is particularly susceptible. It may also indicate establishment failure. This is particularly common where dry weather follows spring planting, prior to new roots developing into the surrounding soil.
The damage is often worse where exposure to wind dries out leaves. The damage is usually worse on the windward side of the plant. In coastal areas, salt-laden winds can also be especially harmful, but this is due to the effect of the salt as well as drying.
- Keep young plants well watered while they establish. This can take from three months to three years, depending on the plant, site and conditions
- Provide shelter from the wind by using a length of shelter fabric (available at garden centres); planting a hedge or shrubs to give protection
- Grow plants that are suited to coastal positions
Blackening within leaves
The blackening of leaves, usually starting along the vein, is due to water-logging. This is common after wet winters on heavy soils and is frequently seen on Aucuba (laurel) as a problem known as aucuba blackening. The roots, when examined, are a bluish-black and fall apart when teased apart. On larger roots the outer sheath may pull away easily, leaving the inner core. There is often a sour smell to both the soil and roots.
Similar leaf symptoms can sometimes be caused by certain foliar diseases, such as Phytophthora ramorum.
- Where waterlogging is a permanent problem, consider installing a drainage system
- Grow plants that thrive in wet soils
- Use raised beds to lift the roots clear of the winter watertable
- See our advice on Phytophthora ramorum for further information where this problem is suspected