As I begin this article, I must confess that I am not an indoor plant expert. Frankly, I think plants belong outside.
In our house, my wife is the houseplant caregiver. That said, we do get lots of questions on houseplants at the Extension office, and this column aims to answer one of the most common - "Why is my (insert your favorite plant here) turning yellow?"
Even the inexperienced recognize yellowing leaves are a pretty good sign that something is wrong with your plant, but unfortunately it can be a sign of almost anything. Yellow leaves can be a symptom of too much or too little water, over or underfertilization, low light conditions and /or pests. How do you figure out what the problem is? Think like a detective.
Has the plant recently been moved? Plants will often shed leaves if they are moved from a location of high humidity to one with low humidity.
Even a new temperature range can cause some stress. Plants need time to acclimate to new environments, and the loss of leaves is their way of readjusting to their surroundings. This type of yellowing and leaf drop usually occurs on the lower, older leaves.
Leaves may yellow if the plant is exposed to a cold draft, so pay attention to plants you keep near windows. Now that cool weather has arrived, your plants will let you know if you have leaky windows or doors. This may cause a lot of leaves all over the plant to yellow and fall off.
If your plant has not been moved and the yellow leaves are new, you need to investigate a little further. Improper watering is another possibility as symptoms of poor watering can take a little time to show up.
Pick the plant up: is it heavy or light? If it is very light, then not enough water is a possible cause of the leaves yellowing. If it is very heavy and soggy, especially if you haven't recently watered, the problem is likely too much water.
Very high light levels can cause yellowing; however, this is unlikely. In the winter, many houseplants suffer from low light levels. The reason for this is twofold: 1) houseplants that spent the summer and fall outdoors are receiving much less light indoors, and 2) these winter days are shorter so even if the plants are in a sunroom or bright window, they're simply not getting as much light.
Sometimes yellowing is caused by insect pests, so you may want to look your plant over thoroughly if you still haven't discovered the cause of its decline. Look on stems and leaves, especially the undersides, for webbing and stippling from spider mites, honeydew from aphids or even the actual insects themselves. A magnifying glass can be helpful in spotting pests, but most of them can be seen with the naked eye.
If nothing else makes sense, fertilization practices should be considered as a possible cause of leaf yellowing. If an entire plant has taken on a light green to yellow cast and the newest leaves are very small, the plant is lacking in nitrogen. Yellowing between the veins on a leaf is also an excellent sign that your plant is hungry and needs fertilizer.
If none of these factors is the culprit, it could be suffering from ‘up and die' disease. This occurs when for no good reason your favorite plant just up and dies! I have diagnosed this several times over the years and still cannot tell you the root cause.
Billy Skaggs is an agricultural agent and Hall County extension coordinator. Phone: 770-531-6988. Fax: 770-531-3994.