Charles:  Thank you for contacting the UVM Extension Master Gardener Helpline asking for help in identifying the cause of your coffee plant leaf-drop.

I reached out to our UVM plant pathologist, Ann, and our "Houseplant Hero" Judy (who you may have seen on several Across the Fence segments giving advice on houseplant care).  I'm forwarding along their thoughts on the problem:

Ann Hazelrigg's comments:   It looks like there is a nutritional issue there and I suspect the pH may be on the higher side since this plant prefers acidic soil. That may be the cause of the iron chlorosis look to the plant. Have they used any fertilizer throughout the summer? I they have, there may also be salts build up.. If not, the plant may benefit from an acidic fertilizer. What do the roots look like? are they mushy brown or healthy white? If healthy and white i would suspect some fertilizer may help. Not many foliar fungal diseases inside homes.  My guess is the iron deficiency. i would have them look at the roots.

Judy's comments:  Yellow leaves usually indicate the coffee plant is suffering from a nutrient deficiency. Iron deficiency can be common. When the leaf veins of an iron deficient plant remain green the rest of the leaf will turn pale yellow. I think that's what we're seeing here. The discoloration is also known as "intercostal chlorosis". Iron deficiency usually occurs when the watering contains too much lime. In the case of iron deficiency, it's best to repot the plant and water with rainwater or distilled water for a while.

Water treatment plants add lime (calcium hydroxide) to drinking water to increase its alkalinity and raise its pH level, which helps to make it less corrosive to pipes (and taste better).

Overfertilizing can lead to chlorosis which causes the leaves to yellow. It's easily remedied with a vigorous flushing to completely clean out any extra fertilizer that's still hanging in there. Or repotting with fresh soil.

Over watering can also cause the leaves to turn yellow before turning brown.

Tips -- Add humidity! and good air circulation (a fan). Add bright, indirect light. Repot. If all else fails - cut the plant back to about two feet (or 1-1/2 ft) and let it regrow! They are resilient. And do not over water.

Hope these tips are helpful. (I have three trees and some starters).

I am also attaching a link to a fact sheet discussing coffee plants from North Carolina State, that you may find interesting.   

Coffea arabica (Arabian Coffee, Coffee, Coffee Plant) | North Carolina Extension Gardener Plant Toolbox

I hope this information helps.  Good luck!

Charles:  Thank you for contacting the UVM Extension Master Gardener Helpline asking for help in identifying the cause of your coffee plant leaf-drop.

I reached out to our UVM plant pathologist, Ann, and our "Houseplant Hero" Judy (who you may have seen on several Across the Fence segments giving advice on houseplant care).  I'm forwarding along their thoughts on the problem:

Ann Hazelrigg's comments:   It looks like there is a nutritional issue there and I suspect the pH may be on the higher side since this plant prefers acidic soil. That may be the cause of the iron chlorosis look to the plant. Have they used any fertilizer throughout the summer? I they have, there may also be salts build up.. If not, the plant may benefit from an acidic fertilizer. What do the roots look like? are they mushy brown or healthy white? If healthy and white i would suspect some fertilizer may help. Not many foliar fungal diseases inside homes.  My guess is the iron deficiency. i would have them look at the roots.

Judy's comments:  Yellow leaves usually indicate the coffee plant is suffering from a nutrient deficiency. Iron deficiency can be common. When the leaf veins of an iron deficient plant remain green the rest of the leaf will turn pale yellow. I think that's what we're seeing here. The discoloration is also known as "intercostal chlorosis". Iron deficiency usually occurs when the watering contains too much lime. In the case of iron deficiency, it's best to repot the plant and water with rainwater or distilled water for a while.

Water treatment plants add lime (calcium hydroxide) to drinking water to increase its alkalinity and raise its pH level, which helps to make it less corrosive to pipes (and taste better).

Overfertilizing can lead to chlorosis which causes the leaves to yellow. It's easily remedied with a vigorous flushing to completely clean out any extra fertilizer that's still hanging in there. Or repotting with fresh soil.

Over watering can also cause the leaves to turn yellow before turning brown.

Tips -- Add humidity! and good air circulation (a fan). Add bright, indirect light. Repot. If all else fails - cut the plant back to about two feet (or 1-1/2 ft) and let it regrow! They are resilient. And do not over water.

Hope these tips are helpful. (I have three trees and some starters).

I am also attaching a link to a fact sheet from North Carolina State, that you may find interesting.   

Coffea arabica (Arabian Coffee, Coffee, Coffee Plant) | North Carolina Extension Gardener Plant Toolbox

I hope this information helps.  Good luck!