I have a lemon tree that I grew from seed 16 years ago. It gets lots of light and water. We live in Tokyo so cold is not a problem. Yet, it has NEVER bloomed. I fertilize it with a general fertilizer, but perhaps that isn't enough. We really want some lemons!
Lemon Tree Doesn’t Bloom
I found this answer while doing research.
I think the lemon thing may have to do with fact that the lemons we see today bear little resemblance to natural lemons, which are small hard fruits with tough skins and tons of seeds. Also extreeeemly bitter. In an attempt to make more and better lemonade, these nasty little fruits were improved to what we see today, a much better lemon. If you go to buy a lemon tree you'll notice they are all grafted clones. They can't be grown from seed, first of all because 99% of the seeds are inert, and secondly because any seed that does sprout will not produce true to form, but will revert to whatever parent stock the tree was engineered from.