How do I know that my orchid is dormant and does not need to be fertilized?
Try to identify it. You can look online or go to your local arborist and they would help you. Gardening is a craft involving patience so do not rush into fertilizing it. Since orchids do not bear fruit and you are not concerned about your yield, your plant will not be affected by late fertilization; a premature, over fertilization can be potentially fatal to your plant, especially if it is still young. Good Luck and Happy Growing!
Different varieties of orchids are dormant at different times. Since you didn't say what your orchid is, it's difficult to answer this question.