Question
QUESTION: I have two Phalaenopsis orchid plants that were repotted in April of 2009. They are hearty plants and only produce new leaves and healthy roots. I cannot get new spikes which were cut off when the plants were repotted in April '09. I do use the MSU fertilizer and they are in a southwest window that gets indirect light in the winter and direct sunlight in the spring and summer. I contol the amount of light by closing and louvering the blinds. What can I do to make them spike? I've had them 4+ years.

Thank you.

ANSWER: If the plant leaves look very healthy and are dark green, this usually signifies too little light for flowering.  The leaves should be a yellow green with even a slightly reddish pigment to indicate adequate light for flowering.  Some phalaenopsis hybrids also like a daily temperature change of at least 10 degrees to set buds.  The  fact that you have flowered them previously, suggests that you try to reproduce the conditions under which they were grown and flowered at that time.

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QUESTION: Thank you for your response. One of the plants has a young leaf which does have the reddish pigment you mention. As I have had these for 4+ years I don't know what to do. They were originally grown in an office so all they had was artifical light 24 hrs a day, and a temperature that probably was cooler at night but not 10 degrees. As it is winter now, and I am in New England, I really can't turn the heat back 10 degrees at night. I have also heard that placing them in a dark, cool environment for 2 weeks or so and then bringing them back to their originalunny site will also work. Have not tried this, but will try anything right now. I don't want to throw them away.
Thank you for your help.

Answer
Thanks for your explanation Jan.  Different growing environment, different results.  You don't need to turn the heat back.  If your plant is on a windowsill or could be so placed, moving the plant closer to the window should drop the temperature near the plant.  In a sunny window, you have the combined effect of cold nights and warmer sunny days to permit this temperature differential.  If you don't have the windowsill option, you might try the option you mentioned.  It shouldn't damage the plant and might achieve the desired result.