I have a ficus macrocarpa that is cycling leaves. It grows new leaves, and drops the larger older leaves. The cycle lasts about a week or so. The base of the tree is always covered with fallen leaves. I don't think that I am under watering. It could be light, but I'm not sure how many lumens ficus needs. It receives 14 hours per day of artificial light. The light is adjusted toward the UV / Blue end of the visual spectrum. Red light light is slightly attenuated. The Ficus is in a greenhouse. Temperature is very steady at ~75 degrees, humidity is about 45 percent. The ficus is potted in a standard bonsai mix that is fairly pores. The plant is watered when it appears to be slightly dry. The mix of leaves is about 60% old leaves, 40% new tiny leaves. growth seems strong. Fertilizer is Bio-Gold, changed every month. I water with water that has been adjusted and filtered. Chloring/Chloramines are filtered, and pH is adjusted to 5.5-6.5. I also have two Chinese elms that were very strong, but are slowly dropping leaves. No disease is evident on plants and only a few flys on tack boards. All maples seem to be stable and healthy. Any ideas why leaves are dropping?

i would say the space is too hot. 25-30 is optimal

hbruch wrote:

14 hours per day of artificial light.
The light is adjusted toward the UV / Blue end of the visual spectrum.
Red light light is slightly attenuated.
I water with water that has been adjusted and filtered.
Chloring/Chloramines are filtered,
pH is adjusted to 5.5-6.5.

My trees are outdoors, in the rain.

My willow leaf ficus does okay in the winter indoors, but drops a lot of leaves, just like yours. Today or tomorrow, outdoors, and it will start growing lots of leaves. This is a pattern it has followed for 20 years.
I don't know what the humidity is, probably around 50% or so. Temperature is room temperature for winter, probably 68F, 20C. Take it outside for some real sunshine.

75 degrees F, sorry I wasn't clear.

Thank you for your reply.
75 degrees F is about 24 C.

Ficus microcarpa is an indoor plant. It's a tropical tree. Our outdoor temperatures at night are still dipping to the upper 30s and lower 40s. Daytime temperatures are in the 60s - 70s.

Ah, ok. Sorry. THat sounds like ideal.

Do you have a picture? I have a hard time understanding what is going on and sometimes a picture tells the story well.

I do not work with filters and PH adjustments. I never know what is being added and what might buildup in the soil that way. But it does not sound like there should be anything wrong, except for the light source perhaps. THere again.. My plants are mostly outside, and the ones inside in winter just sit in the window and I find that is mostly enought; I do provide 5 hrs of supplemental light from a balanced daylight LED array.

Thank you for your help. I think that I have the problem solved. It seems that I have been giving my bonsai to much light. When daylight saving arrived I reset the lights for the new time but all the lights defaulted to 100%. I set the lights back to 50%, and the leaves have stopped dropping at the rate they were falling before. So, a note to everyone; you can give your bonsai too much of anything, including light. After one day the plants have reverted back to green leaves, and seem to have stopped their cycling. I cleaned leaves up this morning and will check them again tomorrow. They look much better.

although I am happy that ypur tree has stopped dropping. leaves, i disagree with your conclusion that it was too bright.

ficus is a tropical canopy species and takes full tropical sun. your lamps will not reach that intensity I am pretty sure.