Answer: Most flowering houseplants, orchids included, will not bloom if they are not getting enough light. This is generally the main reason that orchids do not bloom. Northern exposure is usually not sufficient. A bright western, slightly shaded in the hottest months, or eastern exposure work well. A southern exposure gives you the greatest flexibility. If your window is heavily shaded by trees or adjacent buildings, this will reduce light to your plants and you will have to make adjustments accordingly. If you have bright indirect light, your phals and paphs should do fine. Oncidiums generally need slightly brighter light. Dendrobiums and Cattleyas need the brightest light of all, and do best in a Southern exposure.
If your plants are not getting enough light move them closer to the window. Even a foot can make a huge difference as light falls off very rapidly with increasing distance from a window. During the summer months place plants outdoors in dappled shade if you can. Whenever you move plants into brighter conditions always do so very gradually as you risk burning the leaves.
Best wishes with your orchids!
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