Believe it or not, temperature is the most important factor in getting an orchid to bloom. While the majority of orchids thrive in normal household temperatures, blooms will only occur if there is a difference in the temperature between day and night. This means there needs to be at least a 10 degree (and sometimes more, depending on the species of orchid) difference between the temperature during the day and the temperature at night, with the lower temperature coming at night.
Second to variations in temperature, orchids need the proper amount of light to bloom. Most indoor orchids do well with around four hours of good light per day. To get this amount of light, place the orchids near a window or under artificial growing lights.
While orchids do need direct or indirect light, they cannot get too hot or they will quickly die. If they are placed in direct sunlight for more than six hours, they will probably fail to bloom and eventually die. If your orchid is in a location that may get too hot (including under a heating vent), you will need to keep it cool by increasing its humidity. See Section 3 for how to keep your orchid humid.
Watering and Humidity
Orchids are efficient at storing water and usually only need to be watered once a week. In fact, most beginners overwater their orchids, which is another reason they fail to bloom. Overwatering causes root rot. Some orchids, such as Cattleya and Dendrobium, like to get completely dry before being watered again. Others, such as the popular Paphiopedilum, prefer their soil to be slightly moist at all times, which may necessitate watering twice per week instead of only once per week.
Orchids are air plants, and they like high humidity. If you have low humidity in your house, you need to help your orchids by adding humidity to the air around them. You can do this by misting your orchids once every morning, or by using a humidity tray. Fill a shallow tray with rocks and just a 1/2 inch of water, then set the orchid plant on the tray. The plant should be touching the rocks and not the water.