Answer: The problem can be attributed to light, nutrition and/or temperature. While your orchid is obviously getting the basics, it may not getting exactly what it needs to make it happy enough to bloom lots. Here are a few suggestions:
If you use a regular flowering house plant fertilizer, apply it at half the strength recommended. If you buy a special orchid fertilizer, follow the package directions. Try fertilizing your plants about twice a month. Increase feeding during the spring and summer months when orchids are growing rapidly, and reduce feeding to once a month during the winter. Be sure to rotate in a blossom-booster or flowering plant fertilizer as well. Every month, leach your plants thoroughly-water them with plain water several times and allow them to drain. This helps flush out the fertilizer salts that will build up over time. Most garden supply firms carry a variety of houseplant or orchid fertilizers-you may wish try one or two differentbrands to see what works best.
Most orchids like a day and night temperature variation of about 8 to 10 degrees year 'round, especially to stimulate them to bloom. As night temperatures drop in the fall, or spring, place plants next to a window that is cracked at night to let in a little cool air. Give your plants this treatment for about 3 to 4 weeks and you should begin to see flower stalks emerging soon after. How low should you let the night temperature drop? For paphs and phals, temperatures of about 55 to 60 degrees should suffice. Make sure your plants are not in a cold draft, or protect them with a light curtain. Placing them in an unheated room at night will also do the trick. Remember that day temperatures need to be about ten degrees higher.
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 orchid should do fine.
The yellowing leaf, especially if it is the lowest on the plant, is probably natural. The leaves eventually die and are replaced by new ones. Allow it to turn brown, then gently pull it off the plant.
Orchids need to be repotted when they have absolutely outgrown their pots. Potbound orchids usually bloom better than those with lots of root room.
Best wishes with your orchid.
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