Why are my leaves leathery, limp and wrinkled?
Wrinkled leaves, wilty and leathery leaves usually occur on Phalaenopsis and Paphiopedilum orchids due to two problems: lack of hydration (for one of two reasons) or heat stress.
Lack of hydration is probably the most usual culprit. Either the plant is not being watered enough, or the roots are rotted (usually from over watering) and the plant is not able to obtain water because the roots simply cannot carry the water to the plant. If your plant has aerial roots, look at their condition . Are they silver and wrinkled? If so, your problem may be under watering rather than over watering. While I don't like to recommend constantly unpotting your plants, if your plant is failing, it is often more prudent to check the condition of the roots rather than lose the plant. If you unpot the plant and find the roots hollow, the velamin slipping off , leaving behind a string-like part, then you have a case of root rot. Once your plant has gotten to the point of being limp, leathery, and wrinkled, reviving the plant is usually a long process and often unsuccessful.
Over watering causes root rot and is the most common cause of orchid loss among new growers. Check your method of determining watering. Clean away the rot from the roots, dust (or dab) cut portions on the roots with cinnamon, Physan is also useful. Use rooting hormone on the plant and repot, being careful to keep the plant in reduced light, and increase humidity. Sphag and bag (or it's variants) is often successful in this case. Once the leaf is wrinkled, it rarely comes back to the glossy "hard" state it was before, but it can improve somewhat.
The second cause of wilty leaves is often overheating. Touch the leaves, if they feel warm, then this is your problem. Lights may be too close to the plant, or in the summer, temperatures over 90 do not make for a happy Phal. Increasing humidity and air circulation can be helpful in preventing heat stress.
Extreme cold can also cause wilty leaves, but the leaves are often mushy from freezing and usually have darkened in color.