Q: Why are my orchid leaves turning yellow and drying up? The plants are located in the bathtub where they get sun daily from the south and west window.
A: While it is normal for the oldest leaves of moth orchids (Phalaenopsis) to turn yellow and dry up as they age, when there is uniform yellowing and shriveling of newer leaves, it is a sign of distress. The shriveling suggests there is a lack of water reaching the leaves. Check the root system of your plant. If the roots are in poor condition, they cannot take up water. Overwatering can cause roots to rot. If you haven’t repotted your orchid in a couple years, the potting medium may have broken down and become too dense to allow for good drainage. Bacterial rot also can occur if water is allowed to sit around the center shoot or in the leaf sheaths for a long period of time. Water only in the morning so that your plants can dry out by nightfall. Never let them stand in water and keep the plants in a location where they can get good air circulation, indirect light, and a warm daytime temperature above 75F. Watering instructions can be found in our orchid care video.
See additional information on Phalaenopsis orchid care on the Home & Garden Information Center website.
By Christa K. Carignan, Maryland Certified Professional Horticulturist, Coordinator, University of Maryland Extension Home & Garden Information Center
I try to not comment here because I am not in Maryland. Also, I do not grow Phalaenopsis. (I am guessing that the question is specifically in regard to the orchids in the picture.) Cymbidiums that are very popular here normally get yellowish foliage along with their blooms. In fact, their leaves are sometimes trimmed with scissors to eliminate some of the discoloration (if the whole plants are to be displayed). They can grow like weeds, and those that are too green do not bloom as well as those with some bit of discoloration. Leaves that are shed tend to fall away cleanly and discretely below the viable foliage.