Lots of people must be growing Meyer lemon trees indoors, because lots of people keep asking Grumpy what the heck is wrong with theirs. If you're one of them, console yourself with the thought that these citrus trees are notoriously finicky and often drive their owners nuts. Here's a list of common complaints and what you can do about them.
But first, let's review what these trees require in order to grow well in a pot. They need very bright light, excellent drainage, mild temperatures, and proper fertilization with a fertilizer formulated just for citrus that contains iron, zinc, manganese, and magnesium. Leave out just one of these things and your tree will not be happy.
OK, these are the complaints Grumpy hears most often and actions you should take to keep them from happening again.
"Most of the fruit drops off while it's still small." It's natural for a Meyer lemon to do this, because it often sets much more fruit than it can ripen. (Remember, it's growing in a pot, not in the ground.) Other possible causes -- too much fertilizer at the wrong time (use citrus fertilizer at the rate recommended on the label in spring or summer when the tree is actively growing); soil got too dry after fruit set.
"Most of the flowers fall off before setting fruit." Meyer lemon often does this as a way to prevent setting too much fruit. Other possible causes -- fertilizing at the wrong time; soil got too dry; soil stayed too wet; tree was exposed to cold temperatures.
"Lots of leaves turn yellow and drop at the same time." Something is wrong with the soil. Most often, it's that the roots are staying wet too long. This leads to root rot, leaf drop, and possible death. Citrus trees should NEVER sit in saucer filled with water. When you water, do so thoroughly so that excess water runs out of the drainage hole. Then let the soil go somewhat dry before watering again. Other possible causes -- nutrient deficiencies due to lack of fertilization; exposure to cold; poor drainage and wet soil.
"The lemons stay green and don't ripen." Meyer lemon doesn't ripen like an apple. The process takes a long time. Often the fruit will reach full size and stay green for months before it changes color. So be patient. Other possible causes -- lack of sun; your kids painted the fruits green for a school project.