I grew a lemon tree from a pip 3 years ago, lovely and green but again no blossom. Will it ever flower?

ok if you are tired of waiting and are willing to try radical techniques,
cut through the bark-gently- and remove a band of bark down to the cambium, turn the band 180 degrees, reverse it. This disrupts the phloem enough to cause a bottleneck in the food supply to the roots, the accumulation of carbos could initiate flower formation.

Read more of Lovely Flower