My lemon tree is in a pot. It has abundant fruit, but some are in their second year of growing and they are still very green. They look about the right size for lemons. The tree is about 5 1/2 feet tall.
How Long Does It Take Lemons to Ripen
Certified GKH Gardening Expert
Lemon Trees need plenty of water, sunlight and a regular fertilizer schedule.
Here are a few articles that will help you pinpoint the issues.