Oriental lily growers, especially growers of Star Gazer, are familiar with upper leaf “burn’. Characterised by curled, distorted or dead upper leaves, the disorder is found in greenhouse-grown Oriental hybrid lilies worldwide.
We call this problem “upper leaf necrosis”, or ULN. Described in Asiatic lilies nearly 20 years ago in the Netherlands, ULN was thought to be caused by rapid changes in the greenhouse environment, specifically by bright sunny weather following periods of cloudy, dark days. Our work shows instead that ULN is caused by calcium deficiency. The problem occurs long before you see brown leaf margins and is unrelated to light changes in the greenhouse. 

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