My lemon tree had lots of flowers in early spring, but they dropped off shortly after. I started using 0-10-10 last month, still no fruit.
These articles have information on how to fertilize your trees: https://www.gardeningknowhow.com/edible/fruits/citrus/fertilizing-citrus-trees-best-practices-for-citrus-fertilizing.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm
I would also try giving it some phosphorus rich fertilizer, like bone meal. If it is lacking phosphorus, it will not be able to produce blossoms (which means no fruit.)
The requirements for lemons are very similar to that of limes. If you have not read it yet, this article may also be helpful: https://www.gardeningknowhow.com/edible/fruits/lime/reasons-and-fixes-for-lime-tree-not-producing-blossoms-or-fruit.htm
How to grow and fertilize a (container) lemon tree?
These articles will help: https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm
What type of soil do I need to grow a lemon tree in a pot?
They need the same soil in a pot as they do in the ground--well draining and slightly acidic. This article will help: https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm
I have a 30+ year old lemon tree that was transplanted last year. Ever since it was transplanted, the leaves look droopy and the lemon size is much smaller than usual. We live in northern Illinois so the tree is brought inside during the cold months. How can we make the tree happier?
With a tree that old, most certainly transplant shock is a factor. The older the plant, the longer it needs to recover from it. I would consider this year a loss while the tree recovers and I would make sure that it has optimal water and fertilizer. A fertilizer higher in phosphorous wold be best as this helps with root development You should see it back to full health by next year.
My lime green, pea size Lemons are turning a dirty yellow. What to do?
It sounds like the tree is in the process of aborting the fruit. This can happen for a few reasons. This article will help:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-fruit-drop.htm
Plenty of unripe fruit but the leaves keep falling off. New leaves coming in on top. Live in zone 9, and 85 degrees here.
It is likely stress related, possibly from the heat. Make sure it is getting plenty of water and a little fertilizer may help as well. Leaf drop is a common problem in both lemon and lime citrus trees. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/fruits/lime/lime-tree-leaf-drop-why-a-lime-tree-is-losing-leaves.htm
My lemon tree in a pot drops fruit before they are set.
Most citrus trees will shed fruit if they do not have the nutrients and/or water to support the fruit. You can always expect some fruit drop as the tree evens things out, but if there is a lot of fruit loss, you can fertilize and increase water to the tree to help it keep its remaining fruit. Too much nitrogen fertilizer, however, limits fruit production. Adding more phosphorus should help with this, such as bone meal. This article will also help: https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-fruit-drop.htm