Dwarf Pomegranate Blossoms

How do you get dwarf pomegranates to blossom? I have had one that I bought from you for several years. It is an extremely healthy and attractive green plant, but it has never flowered. Each spring, the green growth is vigorous and lush. I cut it back, and it continues to grow all summer. In the fall, I bring it into a cold greenhouse for the winter. The leaves fall off (as with any deciduous tree), and in the spring when it breaks dormancy, it all starts again. Could the problem be the temperature of the greenhouse, the type of plant food I use, or some other factor?

There could be many reasons for the lack of flowers on your dwarf pomegranate. Pomegranate could be like forthythia and only bloom on last years wood. By trimming the year's growth off you could cut off all wood that might have flowered.
Also plants that are given a lot of nitrogen in their plant food feel no need to do anything other than grow green leaves! To encourage flowers, get a fertilizer with a high middle number and use it all the time. This will compensate for the relatively weak sunlight plants get in our temperate zone latitude. During the summer your plant should be gradually moved into full sun. Take two to three weeks to move it from deep shade to full sun to avoid burning tender foliage.
You could also try to somewhat underpot the plant, as that will often make a plant try to move elsewhere via seeds!