Cymbidium Foliage

Question

Some of my cymbidium leaves are turning black at their bases and now even some of the pseudobulbs are turning black as well. They have received morning sun throughout the winter, during which time they have also had some overhead cover. I live in Southern California. My plants are fertilized monthly over the cooler months. What is likely to be causing the blackness and what should I do to correct it? —C. Duran
 

Answer

First, it has been a fairly wet, cool, winter in Southern California, which has possibly accentuated your plants' ailments. Part of your problem is cosmetic, but the blackening you describe can spread in cool, damp conditions and damage the plant. Without seeing your plants and checking for the causal fungus, I will make my comments more general because cultural practices will often have the greatest influence in either exacerbating or bringing fungal problems under control. Always water early in the day in winter so that the plants are completely dry by nightfall. Check your winter fertilizer and be sure that it is higher in nitrate nitrogen rather than ammonium nitrogen or urea. Tailor your watering to the predicted weather and try to carry plants through rainy spells without watering even if this means the interval between waterings extends by a few days. The one proviso is that you must be willing to get in and water whenever the first warm spring days appear, as a dry plant will really suffer in warm temperatures and your cymbidium flower quality will be undermined. —Andy Easton