Q.My Lemon Tree Is About 3 Years Old I Planted It From A Seed Of A Store Bought Lemon. It Is Looking Wonderful, This Spring I Trans
planted it into a larger pot and it is doing wonderful; the leaves are beautiful and it’s about 16 inches tall and has side sprouts, but I don’t get blossoms or fruit. Why is it? I keep it outdoors in the summer and place it indoors by a sunny window in the winter. Please help me to have it produce fruit. It looks beautiful and is growing well.

Certified GKH Gardening Expert
It can be 6-10 years before you see the first flower, when planted from seed!
This is assuming that you got lucky with the seed genetics. Most lemons are cross pollinated with an inedible, wild, type. Some are cross pollinated with sterile cultivars that do not produce fruit at all!
Unless planted from a clone and grafted to a vigorous root, it is best to assume that your lemon will not flower. It can be disappointing to grow a lemon from seed, expecting fruit, only to find out that it is completely sterile!
Give it 3 to 7 more years, and if you don't see flowers by then, you can safely call the tree sterile.
Here are a couple of articles that will help: https://www.gardeningknowhow.com/edible/fruits/lemons/propagating-lemon-seeds.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm