by Jerry Meislik
Anthony Di Masso, of New York, has a wonderful indoor bonsai collection. He is growing several different Ficus as well as elms, jade and other tropical and sub-tropical plants. His setup includes three metal halide lamps providing the light needs of his trees.
Anthony's indoor setup with metal halide lights, 2011
Recently he has noticed that some of the Ficus are showing yellowing leaves. At least two varieties of Ficus microcarpa are affected.
Anthony writes "I have a question for you. The top leaves on the Ficus microcarpa are a bit yellow. I don't think it would be due to a nitrogen deficiency as I've been using Miracle Grow Liquid fert and that has a very high nitrogen content. Could it be I have it too close to the lights or do you think there is another problem going on?
Ficus microcarpa showing yellow and mic-colored leaves, 2011
I can comfortably leave my hand under the light for any length of time. My hand just gets warm not too hot to move.
The water comes from the tap.
I dont know if this is the same issue with the Green Island but this guy has no trace elements in its soil. All yellow leaves are new and turn that way soon after being put on."
Ficus microcarpa 'Green Island', 2011
Close up view of the leaves, 2011
Chlorosis is a not uncommon problem with plants in cultivation. Basically the normally green leaves get a washed out or yellow color over part or some of the leaves. Determining the exact cause of the coloring problem is often difficult. In this situation with Anthony's plants there are two varieties of Ficus trees being affected with poorly colored leaves; the likely problem lies with some imbalance in the soil, water, or fertilizer routine.
The fertilizer seems fine and definitely not overly strong.
The soil mix is fresh and an open freely-draining mix that should not be too water retentive.
The trace elements are a bit on the heavy side but only one of the trees has had trace elements added.
My suggestion is that the new appartment has a water problem. There may be some major problem with hardness or other chemical problem resulting in dis-colored new leaves.
My suggestion to Anthony is to temporarily change to reverse osmosis, distilled water, or rainwater and continue the normal fertilzer schedule. If the water is the problem Anthony should notice an improved leaf color in 2-3 weeks. Long term if he continues to use r/o, distlled or rain water he may need to switch to a more complete fertilizer as the one he is using is missing key elements.