Question
how do I get new stems to grow on my Phalaenopsis orchids? I have one on which the stem appears to be dead but the leaves are beautiful. And several others with great leaves but no stem growth.

Answer
Palmier, Phalaenopsis flower spikes appear but once per year.  When flowering has finished, the old flower spike may stay green or die back, depending upon the parentage.  You apparently have the type that rebloom on new flower spikes generated during the next flowering season.  You didn't mention how long you have been growing the plants since last flowering.  As long as the plants are healthy, you might try a bloom booster plant food at the rate of about 1/4 tsp per gallon of water.  The usual bloom time for phalaenopsis orchids is the spring time so they could still bloom this year.  Blooming is also promoted by increased light levels.  If your leaves are a deep green, that may be a sign that they are not getting enough light to promote flowering.  Try to raise the light level.