Looks great to me.

Who: 30 year old Calamondin tree with beautiful canopy.

What: Winter leaf drop

When: Fall

Where: Less light and dry air

Why: Not enough photosynthesis

How to stop: Provide a reflective grow tent with higher humidity and supplemental light and actively grow or find a much cooler place to hibernate. Beautiful tree with a stunning canopy. As citrus get larger they are exponentially harder to manage indoors. If money is no object than Gavita Pro 1700e with a gorilla grow tent. Sunlight is 10,000 lumen per square feet measured 1 foot from canopy. Unless windows are in a greenhouse they can't provide the same amount of light a single window can. A cheaper alternative would be to provide 48" Sunblaster strips of LED lighting in a vertical position on 4 sides of the tree. Vertical lighting is better than horizontal lighting with lower power LED like Sunblaster.

Read the WLD (Winter Leaf Drop research) which you can find on this form. It has been posted many times.

https://www.gardena.com/int/garden-life/garden-magazine/everything-you-have-always-wanted-to-know-about-citrus-trees-and-overwintering-them/

Some older leaf drop is normal. Hang a thermometer or get a laser and take reading of temperature around canopy and soil. Try to keep them close and soil temps above 70. If the soil is greatly cooler than ambient air around tree you will get leaf drop. Too much light can actually worsen the condition if roots are cold. A cheap spotlight or two aimed at the top of pot and soil times coming on before any daylight enters the room can get roots going to keep up. You need a growlight for canopy as well.

My canopy grew too large this summer. Added 12" Sunblaster facing upwards to get hard to reach places the overhead light can no longer reach. Even 100,000 lumens can't come close to the quality of the sun.

Citrus, Cacti, Succulents, Photography · More Info