Yellow leaves on a seemingly healthy plant can cause panic. One moment everything seems fine and the next, a lower leaf seems pale, soft, yellow, or completely so. The important thing to know is that the story of one yellow leaf is not complete in itself. It requires additional clues such as soil moisture, placement and light exposure, pot drainage and how else the plant is growing.
Yellowing of an old leaf can be a normal part of plant growth and not a cause of concern. If there is new growth at the top of the plant, a plant may actually be trying to discard this particular lower leaf. In this instance, there is no need to adjust watering schedules, move the plant around to a more suitable position or repot or fertilize immediately. Allow a plant’s lower leaf to become largely yellow or dry and then remove this leaf with a pair of clean pruned pruning shears or scissors, then relax and wait to see what happens with the next few leaves.
As the number of yellow leaves grow, this can provide additional context and insight as to what is happening with your plant. The leaves seem soft or wet and perhaps damp soil in the container, which may be indicative of overwatering or insufficient drainage. First, inspect the soil to the level of the top inch of surface or remove the pot’s inner nursery pot from an outer decorative container and notice if there is standing water within the bottom container. If you are watering and the saucer under the pot is full, it could be causing root rot or other stress that may make other leaves start to yellow and wilt or smell musty.
The position of the plant may also play a factor. A plant that is in low light will have slow growth, wetter soil, and possibly the shedding of an older leaves as insufficient light is not being provided for growth. A plant may be receiving too much sun and show light or sun scald on leaves instead of yellowing evenly. Look at light timing as to when light does hit the plant, where the pot is located, and temperature or heat level of the pot in light or a location where the plant was recently placed or adjusted.
A brief observation period is helpful and can help you avoid overcorrecting. Check moisture level in the potting medium by feeling with the fingers or using wooden probe or stick, check to see if the pot has drainage holes and if the pot is free of cracks, observe and look to either side of other leaves, and see whether leaves are older or newer growths or on the stem and leaves and the amount or intensity of sunlight on the plant. Keep a brief care record or journal. One sentence in the plant’s care record is useful for noting the leaf that changed, the soil moisture reading and where the plant is currently situated. These notes will serve you if the situation reoccurs or the plant begins to show yellowing.
Be gentle when a plant is showing one leaf that is changing. You can overcompensate for one yellow leaf by overwatering, fertilizing, or repotting or pruning, which may cause additional stress. If soil is wet, just wait and monitor the pot’s contents. If pot is sitting in excess water, empty this excess water out. If plant is in the dark in an undesirable spot, consider a brighter location with indirect light that might better suit the plant, then allow a short adjustment period to see if the plant responds positively before moving it again or to another location.
Start to consider the yellow leaves in their current context of overall plant care, asking the questions: is the soil wet or dry, old or new leaf yellowing, good pot drainage, recently repotted or watered, or any recent moves? A single leaf does not tell the full story, but it can alert you that further observation is needed.