What causes leaf burn and how to avoid it?
Leaf burning is a complex phenomenon and is the result of burst leaf cells. A significant cause of rupturing of cell walls is an excessive osmotic effect of the cell content and therefore an excessively strong water influx. The leaf finally discolours from grey to brown and feels dry and crunchy to the touch. Extraneous substances from other flowers/branches in the vase may also contribute to the leaf burn (leaf necrosis).
Avoid the following situations to reduce the chance of leaf burn:
- Excessively long assimilation lighting (extended daylight hours, artificial lighting in the green house) in winter and/or for flower supply for special holidays. The stomata lose the ability to close. The flower’s moisture content continues to evaporate and the flower sucks up too much vase water if flower food has been added. However, without flower food the flower often doesn‘t get enough water
- Weak tissue resulting from lack of light during the last phase of growth, makes the flower sensitive to flower food
- Overdose of flower food from an average of over 150% of the pre-scribed amount
- ‘Toxic’ metal ions in the vase water, such as Zinc, Chlorine, Fluoride and Iron (from well water)
- Use of vase cleaning products, such as chlorine, washing-up liquid and cleaning of sterilising tablets in the correct dosage.
- Slime or other secretions from other flowers/branches in a mixed bouquet in container or vase (for example Narcissus slime)